Ankle and Foot Chapter PDF

Chapter 14 Ankle and Foot DONALD A. NEUMANN, PT, PhD, FAPTA C H A P T E R AT A G...

Chapter 14 Ankle and Foot DONALD A. NEUMANN, PT, PhD, FAPTA C H A P T E R AT A G L A N C E OSTEOLOGY, 595 Distal Tibiofibular Joint, 602 MUSCLE AND JOINT INTERACTION, 627 Basic Terms and Concepts, 595 Talocrural Joint, 602 Innervation of Muscles and Joints, 627 Naming the Joints and Regions, 595 Structure and Function of the Joints Innervation of Muscles, 627 Osteologic Similarities between the Distal Associated with the Foot, 608 Sensory Innervation of the Joints, 629 Leg and the Distal Arm, 596 Subtalar Joint, 608 Anatomy and Function of the Muscles, 629 Individual Bones, 596 Transverse Tarsal Joint (Talonavicular and Extrinsic Muscles, 629 Fibula, 596 Calcaneocuboid Joints), 610 Muscular Paralysis after Injury to the Distal Tibia, 597 Combined Action of the Subtalar and Fibular or Tibial Nerve, 637 Tarsal Bones, 597 Transverse Tarsal Joints, 618 Intrinsic Muscles, 638 Rays of the Foot, 600 Distal Intertarsal Joints, 622 SYNOPSIS, 641 ARTHROLOGY, 600 Tarsometatarsal Joints, 622 ADDITIONAL CLINICAL CONNECTIONS, 642 Terminology Used to Describe Movements, Intermetatarsal Joints, 623 REFERENCES, 648 600 Metatarsophalangeal Joints, 623 STUDY QUESTIONS, 651 Structure and Function of the Joints Interphalangeal Joints, 626 ADDITIONAL VIDEO EDUCATIONAL Associated with the Ankle, 601 Action of the Joints within the Forefoot CONTENT, 652 Proximal Tibiofibular Joint, 601 during the Late Stance Phase of Gait, 626 W alking and running require the foot to be sufficiently as a reference to the terminology used throughout Chapter 14 to pliable to absorb impact as well as to conform to the describe the different phases of the walking or gait cycle. countless spatial configurations between it and the ground. In addition, walking and running require the foot to be relatively rigid in order to transfer potentially large propulsive OSTEOLOGY forces. The healthy foot satisfies the seemingly paradoxical require- ments of shock absorption, pliability, and strength through a Basic Terms and Concepts complex functional and structural interaction among its joints, connective tissues, and muscles. Although not emphasized enough NAMING THE JOINTS AND REGIONS in this chapter, the normal sensation of the healthy foot also provides important measures of protection and feedback to the Fig. 14.1 depicts an overview of the terminology that describes muscles of the lower extremity. the regions of the ankle and foot. The term ankle refers primarily This chapter sets forth a firm basis for an understanding of the to the talocrural joint: the articulation among the tibia, fibula, evaluation and treatment of several disorders that affect the ankle and talus. The term foot refers to all the tarsal bones, and the joints and foot, many of which are kinesiologically related to the move- distal to the ankle. Within the foot are three regions, each consist- ment of the entire lower extremity. Several of the kinesiologic ing of a set of bones and one or more joints. The rearfoot (hind- issues addressed in this chapter are related specifically to the foot) consists of the talus, calcaneus, and subtalar joint; the process of walking and running, topics that are covered in detail midfoot consists of the remaining tarsal bones, including the trans- in Chapters 15 and 16. Figs. 15.10 or 15.11 should be consulted verse tarsal joint and the smaller distal intertarsal joints; and the 595 596 Section IV   Lower Extremity Lateral view Superior (dorsal) Posterior Anterior (proximal) (distal) Tibia Inferior Fibula Talocrural joint (plantar) Tarsa ls Subtalar Talus Me joint tata rsals Phalang es Calcaneus Transverse tarsal joint Rearfoot Midfoot Forefoot FIG. 14.1 Overall organization of the bones, major joints, and regions of the foot and ankle. TABLE 14.1 Structural Organization of the Bones and Joints of the Ankle and Foot Ankle Foot FIG. 14.2 Topographic similarities between a pronated forearm and the Bones Tibia Rearfoot: Calcaneus and talus* ankle and foot. Note that the thumb and great toe are both located on Fibula Midfoot: Navicular, cuboid, and the medial side of their respective extremity. Talus cuneiforms Forefoot: Metatarsals and phalanges Joints Talocrural joint Rearfoot: Subtalar joint Proximal Midfoot: Transverse tarsal joint: tibiofibular talonavicular and joint calcaneocuboid; distal intertarsal Distal joint: cuneonavicular, tibia in the leg each articulates with a set of small bones—the tibiofibular cuboideonavicular, and carpus and tarsus, respectively. When the pisiform of the wrist is joint intercuneiform and cuneocuboid complex considered as a sesamoid bone (in contrast to a separate carpal Forefoot: Tarsometatarsal, bone), the carpus and tarsus have seven bones each. The general intermetatarsal, anatomic plan of the metatarsus and metacarpus, as well as the metatarsophalangeal, more distal phalanges, is remarkably similar. A notable exception interphalangeal joints is that the first (great) toe in the foot is not as functionally devel- oped as the thumb in the hand. *Talus is included as a bone of the ankle and of the foot. As described in Chapter 12, the long bones of the lower extremity progressively internally (or medially) rotate during embryologic development. As a result, the great toe is positioned on the medial side of the foot, and the top of the foot is actu- ally its dorsal surface. This orientation is similar to that of the forefoot consists of the metatarsals and phalanges, including all hand when the forearm is fully pronated (Fig. 14.2). This plan- joints distal to and including the tarsometatarsal joints. With Fig. tigrade position of the foot is necessary for walking and standing. 14.1 as a backdrop, Table 14.1 provides a summary of the orga- With the forearm pronated, flexion and extension of the wrist nization of the bones and joints of the ankle and foot. are similar to plantar flexion and dorsiflexion of the ankle, The terms anterior and posterior have their conventional mean- respectively. ings with reference to the tibia and fibula (i.e., the leg). When describing the ankle and foot, however, these terms are often used Individual Bones interchangeably with distal and proximal, respectively. The terms dorsal and plantar describe the superior (top) and inferior aspects FIBULA of the foot, respectively. The long and thin fibula is located lateral and parallel to the tibia OSTEOLOGIC SIMILARITIES BETWEEN THE DISTAL LEG AND (Fig. 14.3). The fibular head can be palpated just lateral to the THE DISTAL ARM lateral condyle of the tibia. The slender shaft of the fibula transfers only about 10% of body weight through the leg; most of the The ankle and foot have several features that are structurally weight is transferred through the thicker tibia. The shaft of the similar to the wrist and hand. The radius in the forearm and the fibula continues distally to form the sharp and easily palpable  Chapter 14   Ankle and Foot 597 Anterior view nally rotated position of the foot during standing. This twist of the lower leg is referred to as external (lateral) tibial torsion, based on the orientation of the bone’s distal end relative to its proximal end. Interosseous ligament TARSAL BONES The seven tarsal bones are shown in four different perspectives in Talocrural joint Fibula Tibia Figs. 14.4 through 14.7. Anterior tibiofibular ligament Medial malleolus Lateral malleolus Osteologic Features of the Tarsal Bones Head of talu s TALUS Trochlear surface Deltoid ligament (cut) Head Neck Anterior, middle, and posterior facets FIG. 14.3 An anterior view of the distal end of the right tibia and fibula, Talar sulcus and the talus. The articulation of the three bones forms the talocrural Lateral and medial tubercles (ankle) joint. The dashed line shows the proximal attachment of the capsule of the ankle joint. CALCANEUS Tuberosity Lateral and medial processes Anterior, middle, and posterior facets Calcaneal sulcus Sustentaculum talus lateral malleolus (from the Latin root malleus, hammer). The NAVICULAR lateral malleolus functions as a pulley for the tendons of the fibu- Proximal concave (articular) surface laris (peroneus) longus and brevis. On the medial surface of the Tuberosity lateral malleolus is the articular facet for the talus (see ahead Fig. MEDIAL, INTERMEDIATE, AND LATERAL CUNEIFORMS 14.11). In the articulated ankle, this facet forms part of the talo- Transverse arch crural joint (Fig. 14.3). CUBOID Groove (for the tendon of the fibularis longus) DISTAL TIBIA The distal end of the tibia broadens to allow greater contact area for transferring loads across the ankle. On its medial side is the prominent medial malleolus. On the lateral surface of the Talus medial malleolus is the articular facet for the talus (see ahead The talus is the most superiorly located bone of the foot. Its dorsal Fig. 14.11). In the articulated ankle, this facet forms a small or trochlear surface is a rounded dome: convex anterior-posteriorly part of the talocrural joint. On the lateral side of the distal tibia and slightly concave medial-laterally (see Figs. 14.4 and 14.6).170 is the fibular notch, a triangular concavity that accepts the Cartilage covers the trochlear surface and its adjacent sides, pro- distal end of the fibula at the distal tibiofibular joint (see ahead viding smooth articular surfaces for the talocrural joint. The Fig. 14.11). prominent head of the talus projects forward and slightly medially In the adult the distal end of the tibia is twisted externally toward the navicular (see Fig. 14.3). In the adult, the long axis of around its long axis approximately 20 or 30 degrees relative to its the neck of the talus positions the head of this bone about 30 proximal end. This natural torsion is evident by the slight exter- degrees medial to the sagittal plane. In small children, the head is projected medially about 40 to 50 degrees, partially accounting for the often inverted appearance of their feet. Fig. 14.8 shows three articular facets on the plantar (inferior) surface of the talus. The anterior and middle facets are slightly curved and often continuous with each other. The articular car- Osteologic Features of the Fibula and Distal Tibia tilage that covers these facets also covers part of the adjacent head FIBULA of the talus. The oval, concave posterior facet is the largest facet. Head As a functional set, the three facets articulate with the three facets Lateral malleolus on the dorsal (superior) surface of the calcaneus, forming the Articular facet (for the talus) subtalar joint. The talar sulcus is an obliquely running groove DISTAL TIBIA between the anterior-middle and posterior facets. Medial malleolus Lateral and medial tubercles are located on the posterior-medial Articular facet (for the talus) surface of the talus (see Fig. 14.4). A groove formed between these Fibular notch tubercles serves as a pulley for the tendon of the flexor hallucis longus (see ahead Fig. 14.12). 598 Section IV   Lower Extremity Calcaneus 14.7). The more extensive dorsal surface contains three facets that The calcaneus, the largest of the tarsal bones, is well suited to join the matching facets on the talus (see Fig. 14.8). The anterior accept the impact of heel strike during walking. The large and and middle facets are relatively small and nearly flat. The posterior rough calcaneal tuberosity receives the attachment of the Achilles facet is large and convex, conforming to the concave shape of the tendon. The plantar surface of the tuberosity has lateral and medial equally large posterior facet on the talus. Between the posterior and processes that serve as attachments for many of the intrinsic muscles medial facets is a wide oblique groove called the calcaneal sulcus. and the deep plantar fascia of the foot (see Fig. 14.5). Located within this sulcus are the attachments of several strong liga- The calcaneus articulates with other tarsal bones on its anterior ments that bind the subtalar joint. With the subtalar joint articu- and dorsal surfaces. The relatively small, curved anterior surface of lated, the sulci of the calcaneus and talus form a canal within the the calcaneus joins the cuboid at the calcaneocuboid joint (see Fig. subtalar joint, known as the tarsal sinus (see Fig. 14.7). Superior view Inferior view Interphalangeal joint Extensor digitorum longus and brevis Flexor digitorum longus Distal and proximal Flexor digitorum brevis Flexor hallucis longus Extensor interphalangeal joints hallucis longus Head Phalanges Dorsal interossei Adductor hallucis and Shaft flexor hallucis brevis Distal phalanx Extensor Base digitorum brevis Middle phalanx Plantar interossei Abductor and flexor Head Proximal phalanx hallucis brevis 1st 2nd 3rd 4th Dorsal interossei Abductor and Lateral and medial flexor digiti minimi als Shaft 5th sesamoid bones Metatars Adductor hallucis Base Metatarsal (oblique head) Medial cuneiform Fibularis tertius Plantar interossei Fibularis longus Fibularis brevis Intermediate cuneiform Abductor and Tibialis anterior flexor digiti minimi cess ro loid Navicular Groove for Tibialis posterior ty S Cuneiforms p Tuberosity fibularis longus Cu Lateral cuneiform boid Head Flexor hallucis brevis Navicular Talus Neck Cuboid Trochlea Extensor digitorum Quadratus plantae Talus brevis Sustentaculum talus Calcaneus Groove for flexor hallucis longus Medial and lateral tubercles of talus Abductor Flexor digitorum brevis digiti minimi and abductor hallucis Calcaneus Lateral process Medial process Achilles tendon Calcaneal attaching to tuberosity tuberosity FIG. 14.5 An inferior (plantar) view of the bones of the right foot. Proxi- FIG. 14.4 A superior (dorsal) view of the bones of the right foot. Proximal mal attachments of muscles are indicated in red, distal attachments in attachments of muscles are indicated in red, distal attachments in gray. gray. Medial view chlea Facet for Neck Tro medial malleolus Hea d us Medial tubercle Ta l Na cuMed ul vic ar ne ia eus ifo l lcan tarsal rm Ca eta Distal tm phalanx 1s Sustentaculum talus Calcanea l Navicular y tuberosity tuberosit Middle Proximal phalanx phalanx FIG. 14.6 A medial view of the bones of the right foot.  Chapter 14   Ankle and Foot 599 Lateral view lu s Facet for articulation Ta Navicular with lateral malleolus Cuneiforms Subtalar joint (posterior articulation) 2nd m etat Cuboid ars eu s al lcan Ca 5th m etat a rsa l Tarsal Styloid sinus process Proximal Middle Distal phalanx phalanx phalanges FIG. 14.7 A lateral view of the bones of the right foot. Superior view tatarsal Me s Tibialis anterior Cunei form tendon s Anterior facet FIG. 14.8 A superior view of the talus flipped laterally id to reveal its plantar surface as well as the dorsal surface ic ular Talu s Middle facet of the calcaneus. With the talus moved, it is possible bo av Cu Socket for Interosseous to observe the three articular facets located on the talus N head of talus ligament and on the calcaneus. Note also the deep, continuous within concavity formed by the proximal side of the navicular talar sulcus and the spring ligament. This concavity accepts the Spring ligament head of the talus, forming the talonavicular joint. (The interosseous and cervical ligaments and multiple Tibialis posterior tendons have been cut.) Flexor digitorum longus Anterior facet Middle facet Posterior facets Interosseous ligament within calcaneal sulcus Cervical ligament Flexor hallucis longus Calcaneus Calcaneal (Achilles) tendon Medial, Intermediate, and Lateral Cuneiforms The cuneiform bones (from the Latin root meaning “wedge”) act as a spacer between the navicular and bases of the three medial The sustentaculum talus projects medially as a horizontal shelf metatarsal bones (see Fig. 14.4). The cuneiforms contribute to the from the dorsal surface of the calcaneus (see Fig. 14.6). The sus- transverse arch of the foot, accounting, in part, for the transverse tentaculum talus lies under and supports the middle facet of the convexity of the dorsal aspect of the midfoot. talus. (Sustentaculum talus literally means a “shelf for the talus.”) Cuboid Navicular As its name indicates, the cuboid has six surfaces, three of which The navicular is named for its resemblance to a ship (i.e., referring articulate with adjacent tarsal bones (see Figs. 14.4, 14.5, and to “navy”). Its proximal (concave) surface accepts the head of the 14.7). The distal surface articulates with the bases of both the talus at the talonavicular joint (see Fig. 14.4). The distal surface fourth and the fifth metatarsals. The cuboid is therefore homolo- of the navicular bone contains three relatively flat facets that gous to the hamate bone in the wrist. articulate with the three cuneiform bones. The entire, curved proximal surface of the cuboid articulates The medial surface of the navicular has a prominent tuberosity, with the calcaneus (see Fig. 14.4). The medial surface has an oval palpable in the adult at about 2.5 cm inferior and distal (anterior) facet for articulation with the lateral cuneiform and a small facet to the tip of the medial malleolus (see Fig. 14.6). This tuberosity for articulation with the navicular. A distinct groove runs across serves as one of several distal attachments of the tibialis posterior the plantar surface of the cuboid, which in life is occupied by the muscle. tendon of the fibularis longus muscle (see Fig. 14.5). 600 Section IV   Lower Extremity RAYS OF THE FOOT Talocrural joint A ray of the forefoot is functionally defined as one metatarsal and its associated set of phalanges. Talus Talonavicular Metatarsals joint The five metatarsal bones link the distal row of tarsal bones with Subtalar the proximal phalanges (see Fig. 14.4). Metatarsals are numbered joint 1 through 5, starting on the medial side. The first metatarsal is the shortest and thickest, and the second is usually the longest. The second and usually the third metatarsals are the most rigidly attached to the distal row of tarsal bones. These morphologic characteristics generally reflect the larger forces that pass through this region of the forefoot during the push off phase of gait. Each metatarsal has a base at its proximal end, a shaft, and a convex head at its distal end (see Fig. 14.4, first metatarsal). The bases of the metatarsals have small articular facets that mark the site of Calcaneocuboid joint articulation with the bases of the adjacent metatarsals. FIG. 14.9 A radiograph from a healthy person showing the major joints Longitudinally, the shafts of the metatarsals are slightly concave of the ankle and foot: talocrural, subtalar, talonavicular, and calcaneocu- on their plantar side (see Fig. 14.6). This arched shape enhances boid. The talonavicular and calcaneocuboid joints are part of the larger the load-supporting ability of the metatarsals, and provides space transverse tarsal joint. Note the central location of the talus. for muscles and tendons. The plantar surface of the first metatarsal head has two small facets for articulation with two sesamoid bones that are imbedded within the tendon of the flexor hallucis brevis (see Fig. 14.5). The fifth metatarsal has a prominent styloid process joints: talocrural, subtalar, and transverse tarsal (Fig. 14.9). As will just lateral to its base, marking the attachment of the fibularis be described, the talus is mechanically involved with all three of brevis muscle (see Fig. 14.7). these joints. The multiple articulations made by the talus help to explain the bone’s complex shape, with nearly 70% of its surface covered with articular cartilage. An understanding of the shape of the talus is crucial to understanding much of the kinesiology of the Osteologic Features of a Metatarsal ankle and foot. Base (with articular facets for articulation with the bases of adjacent metatarsals) Terminology Used to Describe Movements Shaft Head The terminology used to describe movements of the ankle and Styloid process (on the fifth metatarsal only) foot incorporates two sets of definitions: a fundamental set and an applied set. The fundamental terminology defines movement of the foot or ankle as occurring at right angles to the three standard axes of rotation (Fig. 14.10A). Dorsiflexion (extension) and plantar Phalanges flexion describe motion that is parallel to the sagittal plane, around As in the hand, the foot has 14 phalanges. Each of the four lateral a medial-lateral axis of rotation. Eversion and inversion describe toes contains a proximal, middle, and distal phalanx (see Fig. motion that is parallel to the frontal plane, around an anterior- 14.4). The first toe—more commonly called the great toe or posterior axis of rotation. Abduction and adduction describe hallux—has two phalanges, designated as proximal and distal. In motion that is parallel to the horizontal (transverse) plane, around general, each phalanx has a concave base at its proximal end, a a vertical (superior-inferior) axis of rotation. For at least the three shaft, and a convex head at its distal end. major joints of the ankle and foot, these fundamental definitions are inadequate because most movements at these joints occur about an oblique axis rather than about the three standard, orthog- Osteologic Features of a Phalanx onal axes of rotation depicted in Fig. 14.10A. A second and more applied terminology has therefore evolved in Base Shaft the attempt to define the movements that occur perpendicular to Head the prevailing oblique axes of rotation at the ankle and foot (see Fig. 14.10B). Pronation is defined as a motion that has elements of eversion, abduction, and dorsiflexion. Supination, in contrast, is defined as a motion that has elements of inversion, adduction, ARTHROLOGY and plantar flexion. The orientation of the oblique axis of rotation depicted in Fig. 14.10B varies across the major joints but, in Depending on the chosen nomenclature, one could argue that up general, has a pitch that is similar to that illustrated. The exact to 14 named joints or joint complexes are structurally or function- pitch of each major joint’s axis of rotation is described in subse- ally associated with the ankle and foot. Although all these joints quent sections. contribute to the kinesiologic function of the region, this chapter Pronation and supination motions have been called “triplanar” spends considerable attention to the interaction of three major motions. Unfortunately, this description is misleading. The term  Chapter 14   Ankle and Foot 601 Fundamental movement definitions Applied movement definitions PRONATION: SUPINATION: ABDUCTION/ EVERSION INVERSION ADDUCTION ABDUCTION ADDUCTION (vertical axis) DORSIFLEXION PLANTAR FLEXION EVERSION/ INVERSION Lateral (AP axis) view Oblique axis DORSIFLEXION/ A PLANTAR B FLEXION (ML axis) FIG. 14.10 (A) Fundamental movement definitions are based on the movement of any part of the ankle or foot in a plane perpendicular to the three standard axes of rotation: vertical, anterior-posterior (AP), and medial-lateral (ML). (B) Applied movement definitions are based on the movements that occur at right angles to one of several oblique axes of rotation within the foot and ankle. The two main movements are defined as either pronation or supination. TABLE 14.2 Terms That Describe Movements and Deformities of the Ankle and Foot Motion Axis of Rotation Plane of Motion Example of Fixed Deformity or Abnormal Posture Plantar flexion Pes equinus Dorsiflexion } Medial-lateral Sagittal Pes calcaneus Inversion Varus Eversion } Anterior-posterior Frontal Valgus Abduction Adduction } Vertical Horizontal Abductus Adductus } Supination Varying elements of inversion, Inconsistent terminology—usually implies one or Oblique (varies by adduction, and plantar flexion more of the components of supination Pronation joint) Varying elements of eversion, Inconsistent terminology—usually implies one or abduction, and dorsiflexion more of the components of pronation triplanar implies only that the movements “cut through” each PROXIMAL TIBIOFIBULAR JOINT of the three cardinal planes, not that the joint exhibiting this movement possesses three degrees of freedom. Pronation and The proximal (or superior) tibiofibular joint is a synovial joint supination share a given plane. Table 14.2 summarizes the termi- located lateral to and immediately inferior to the knee. The joint nology used to describe the movements of the ankle and foot, is formed between the head of the fibula and the posterior-lateral including the terminology that describes abnormal posture or aspect of the lateral condyle of the tibia (see Fig. 13.4). The joint deformity. surfaces are generally flat or slightly oval, covered by articular cartilage.175 Although the proximal tibiofibular joint is function- Structure and Function of the Joints Associated ally independent of the knee (tibiofemoral) joint, anatomic con- with the Ankle nections exist between the capsules of the two joints.145 A capsule strengthened by anterior and posterior ligaments and From an anatomic perspective, the ankle includes one functional part of the tendon of the biceps femoris encloses the proximal articulation: the talocrural joint. An important structural compo- tibiofibular joint (see Figs. 13.7 and 13.9). The tendon of the nent of this joint is the articulation formed between the tibia and popliteus muscle provides additional stabilization as it crosses the fibula—an articulation reinforced by the proximal and distal tib- joint posteriorly. When stressed by forces and torques generated iofibular joints and the interosseous membrane of the leg (see Fig. while walking, 1–3 mm of anterior and posterior translations 13.3). Because of this functional association, the proximal and have been measured at this joint in cadaver specimens.162 The distal tibiofibular joints are included under the topic of the relative stability at this joint is needed to ensure that forces “ankle.” within the biceps femoris and lateral collateral ligament of the 602 Section IV   Lower Extremity Anterior-lateral view Posterior view T Interosseous F i T ligament i Fibular i F b i b notch i b Groove for tendons u Groove for tendons i b of fibularis longus a u l of tibialis posterior and a and brevis a flexor digitorum longus l a Posterior tibiofibular Posterior tibiofibular s ligament malleolu ligament Medial Inferior transverse Anterior tibiofibular ligament ligament (cut) Posterior malleolu Lateral tibiotalar Articular facet Deltoid (deep) fibers Lateral ligament s malleolus for talus Deltoid ligament Tibiocalcaneal (cut) Posterior talofibular fibers ligament FIG. 14.11 An anterior-lateral view of the right distal tibiofibular joint with the fibula reflected to show the articular surfaces. Groove for tendon Calcaneofibular of flexor hallucis longus ligament Achilles tendon knee are transferred effectively from the fibula to the tibia. (cut) Although rare, acute dislocation of the proximal tibiofibular joint secondary to trauma has been described in the literature.77 FIG. 14.12 Posterior view of the right ankle region shows several liga- ments of the distal tibiofibular, talocrural, and subtalar joints. The dashed DISTAL TIBIOFIBULAR JOINT line indicates the proximal attachments of the capsule of the talocrural (ankle) joint. The distal tibiofibular joint is formed by the articulation between the medial surface of the distal fibula and the fibular notch of the tibia (Fig. 14.11). Anatomists frequently refer to the distal tibio- The shape of the fibular joint as a syndesmosis, which is a type of fibrous synarthro- talocrural joint dial joint that is closely bound by an interosseous membrane. As described ahead, movement is slight at the distal tibiofibular joint, and appears to be primarily associated with dorsiflexion at the talocrural joint. A carpenter’s Tibia mortise joint The interosseous ligament provides the strongest bond between the distal end of the tibia and fibula (see Fig. 14.3). This ligament is an extension of the interosseous membrane between the tibia and Fibula fibula. The anterior and posterior (distal) tibiofibular ligaments also Talus stabilize the joint (Figs. 14.11 and 14.12). A stable union between the distal tibia and fibula is essential to the stability and function of the talocrural joint.199 A B Ligaments of the Distal Tibiofibular Joint FIG. 14.13 The similarity in shape of the talocrural joint (A) and a car- Interosseous ligament (membrane) penter’s mortise joint (B) is demonstrated. Note the extensive area of the Anterior tibiofibular ligament talus that is lined with articular cartilage (blue). Posterior tibiofibular ligament compressive forces pass through the talus and tibia; the remaining TALOCRURAL JOINT 5% to 10% pass through the lateral region of the talus and the fibula.25 The talocrural joint is lined with about 3 mm of articular Articular Structure cartilage, which can be compressed by 30% to 40% in response The talocrural joint, or ankle, is the articulation of the trochlea to peak physiologic loads.198 This load-absorption mechanism (dome) and sides of the talus with the rectangular cavity formed protects the intra-articular subchondral bone from damaging by the distal end of the tibia and both malleoli (see Figs. 14.3 and stress. 14.9). The talocrural joint is often referred to as the “mortise,” owing to its resemblance to the wood joint used by carpenters Ligaments (Fig. 14.13). The concave shape of the proximal side of the The articular capsule of the talocrural joint is reinforced by mortise is maintained by ligaments that bind the tibia with the collateral ligaments that help maintain the stability between the fibula. The confining shape of the talocrural joint provides a major talus and the rectangular “socket” of the mortise. In addition to source of natural stability to the ankle.189,199 adding mechanical strength to the mortise, ligaments possess The structure of the mortise must be sufficiently stable to mechanoreceptors (primarily free nerve and Ruffini endings) that accept the forces that pass between the leg and foot. Although ultimately enhance the ability of muscles to subconsciously stabi- variable, while standing approximately 90% to 95% of the lize the region.147  Chapter 14   Ankle and Foot 603 The medial collateral ligament of the talocrural joint is often mortise and by the lateral collateral ligaments.26,199,201 Injury of called the deltoid ligament, because of its triangular shape. The the deltoid ligament is relatively uncommon, in part because of apex of the triangular ligament is attached along the distal medial the ligament’s strength and also because the lateral malleolus malleolus, with its base thickening and expanding to typically serves as a bony block against excessive eversion. Injuries that do include a superficial set of four bands of fibers (Fig. 14.14).26 The occur are often associated with trauma to other structures, such specific distal attachment points of the superficial fibers are high- as the distal tibiofibular joint (syndesmosis), lateral collateral liga- lighted in Fig. 14.14 and listed in the box. A deep set of shorter ments, spring ligament (formally described ahead), and bone vertical fibers exist in a separate plane, attaching between the (fracture and bruising).88,159 This cluster of associated injuries may medial malleolus and adjacent medial side of the talus. These deep be severe, frequently occurring while landing awkwardly from a anterior and posterior tibiotalar fibers (which are not visible in jump or from extreme twisting of the loaded lower limb, often Fig. 14.14) attach close to the medial side of the talocrural joint. combining the extremes of eversion and abduction (external rota- The deep posterior tibiotalar fibers attaching above and anterior tion). (The literature often uses the terms abduction and external to the medial tubercle of the talus are the largest and thickest fibers rotation of the ankle interchangeably. While weight bearing over of the entire deltoid ligament (Fig. 14.12).26 the foot, excessive abduction of the ankle occurs by way of exces- sive internal rotation of the lower leg relative to the fixed talus.) The lateral collateral ligaments of the ankle include the anterior Distal Attachments of the Fibers Comprising the Deltoid and posterior talofibular and the calcaneofibular ligaments. Unlike Ligament the intertwined deltoid ligaments, the lateral ligaments exist as separate anatomic entities (Fig. 14.15). The mechanics of the SUPERFICIAL SET typical “sprained ankle” usually involve a component of excessive Tibionavicular fibers attach to the navicular, above its tuberosity just distal to the talonavicular joint line. inversion. Not surprisingly therefore, about 80% of all ankle Tibiospring fibers blend with the plantar calcaneonavicular sprains are associated with injury to one or more of the lateral (“spring”) ligament of the midfoot. collateral ligaments.89,201 The relative high frequency of inversion Tibiocalaneal fibers attach to the sustentaculum talus of the sprains can be partially explained by the slight inversion of the calcaneus. calcaneus at the instant the heel contacts the ground while Tibiotalar fibers attach just anterior to the medial tubercle of the walking, coupled with the inability of the medial malleolus to talus. adequately block the medial side of the mortise. DEEP SET The anterior talofibular ligament attaches to the anterior aspect Anterior and posterior tibiotalar fibers attach along much of the of the lateral malleolus, then courses anteriorly and medially to medial surface of the talus, close to and following the talocrural the neck of the talus (see Fig. 14.15). This ligament is the most joint line. frequently injured of the lateral ligaments.57 Injury is often caused by excessive inversion or by horizontal plane adduction (internal rotation) of the ankle, especially when combined with plantar The primary function of the deltoid ligament is to reinforce the flexion—for example, when inadvertently stepping into a hole or medial side of the ankle. As a whole, the fibers are oriented to onto someone’s foot while landing from a jump. The calcaneofibu- limit the extremes of eversion across the talocrural, subtalar, and lar ligament courses inferiorly and posteriorly from the apex of talonavicular joints. Fibers also provide multidirectional rotatory the lateral malleolus to the lateral surface of the calcaneus (see Fig. stability to the mortise, a function shared by the shape of the 14.15). This ligament primarily resists inversion across the Lateral view F Deltoid Tibionavicular fibers Medial view Posterior i ligament tibiofibular Anterior tibiofibular ligament Tibiospring fibers b (superficial T ligament u Tibiocalcaneal fibers i Anterior talofibular ligament fibers) Tibiotalar fibers l b Posterior a i talofibular Cervical ligament Dorsal talonavicular a Medial malleolus ligament Bifurcated ligament ligament Achilles Dorsal tarso- Dorsal cuneonavicular metatarsal ligament tendon ligaments Achilles tendon (cut) Dorsal tarsometatarsal ligaments al tars m eta t Fibularis brevis 1s Calcaneofibular tendon (cut) Tibialis posterior Long plantar Plantar calcaneonavicular tendon (cut) ligament (spring) ligament ligament Dorsal calcaneocuboid ligament FIG. 14.14 Medial view of the right ankle region highlights the deltoid Fibular retinaculum Fibularis longus tendon (cut) (medial collateral) ligament. The distal attachment points of the four sets FIG. 14.15 Lateral view of the right ankle region highlights the lateral of superficial fibers are indicated by black dots. collateral ligaments. 604 Section IV   Lower Extremity talocrural joint (especially when fully dorsiflexed) and the subtalar medial malleolus, forming part of the posterior wall of the talo- joint. As a pair, the calcaneofibular and anterior talofibular liga- crural joint. ments provide resistance to inversion throughout most of the In summary, the medial and lateral collateral ligaments of the range of ankle dorsiflexion and plantar flexion. About two-thirds ankle limit excessive eversion and inversion of the ankle, respec- of all lateral ankle ligament injuries involve both of these tively. Furthermore, because most of the ligaments course obliquely ligaments.58 in varying anterior or posterior directions, most also limit anterior or posterior translations of the talus within the mortise.60,199 As described in the section on arthrokinematics, the movements Three Major Components of the Lateral Collateral of plantar flexion and dorsiflexion are therefore kinematically Ligaments of the Ankle linked to anterior and posterior translation of the talus, respec- tively. For these reasons, several of the collateral ligaments are Anterior talofibular ligament Calcaneofibular ligament stretched at the extremes of dorsiflexion or plantar flexion of the Posterior talofibular ligament talocrural joint. Many of the components of the ligaments that cross the talocrural joint also cross other joints of the foot, such as the subtalar and talonavicular joints. These ligaments therefore The posterior talofibular ligament originates on the posterior- provide stability across multiple joints. Table 14.3 provides a medial side of the lateral malleolus and attaches to the lateral summary of selected movements that stretch the major liga- tubercle of the talus (see Figs. 14.12 and 14.15). Its fibers run ments of the ankle. This information helps explain several nearly horizontally across the posterior side of the talocrural joint, aspects of clinical practice, including the mechanisms by which in an oblique anterior-lateral to posterior-medial direction (Fig. ligaments are injured, the reasoning for how certain stress tests 14.16). The primary function of the posterior talofibular ligament can assess the integrity of ligaments, and the rationale behind is to stabilize the talus within the mortise. In particular, it limits forms of manual therapy performed to increase the extent of excessive abduction (external rotation) of the talus, especially movement. when the ankle is fully dorsiflexed.31,60 The inferior transverse ligament is a small thick strand of fibers Osteokinematics considered part of the posterior talofibular ligament (see Fig. The talocrural joint possesses one primary degree of freedom. 14.12). The fibers attach medially to the posterior aspect of the Although dissimilar biomechanical descriptions have been pub- lished,170 this chapter assumes that rotation at the talocrural joint occurs primarily around an axis of rotation that passes through the body of the talus and through the tips of both malleoli.84 Because Superior view the lateral malleolus is inferior and posterior to the medial mal- leolus (which can be verified by palpation), the axis of rotation departs slightly from a pure medial-lateral axis. As depicted in Fig. 14.17A–B, the axis of rotation (in red) is inclined slightly superiorly and anteriorly as it passes laterally to medially through the talus and both malleoli.113 The axis deviates from a pure Fibularis medial-lateral axis about 10 degrees in the frontal plane (see tertius Fig. 14.17A) and 6 degrees in the horizontal plane (see Fig. Extensor 14.17B). Because of the pitch of the axis of rotation, dorsiflex- hallucis longus Extensor digitorum longus ion is associated with slight abduction and eversion, and plantar Tibialis anterior flexion with slight adduction and inversion.167 By strict definition, Extensor digitorum brevis therefore, the talocrural joint produces a movement of pronation muscle (cut) and supination. Because the axis of rotation deviates only mini- Inferior mally from the pure medial-lateral axis, the main components of extensor Inferior extensor retinaculum retinaculum pronation and supination at the talocrural joint are overwhelm- ingly dorsiflexion and plantar flexion (see Fig. 14.17D–E).110,169 Talus Medial The horizontal and frontal plane components of pronation malleolus Lateral malleolus and supination are indeed small, and ignored in most clinical situations. Fibularis brevis The 0-degree (neutral) position at the talocrural joint is defined Tibialis posterior Fibularis longus by the foot held at 90 degrees to the leg. From this position, the Flexor digitorum talocrural joint permits about 15 to 25 degrees of dorsiflexion and Posterior talofibular longus ligament 40 to 55 degrees of plantar flexion, although reported values differ Flexor hallucis longus considerably based on type and method of measurement.18,66,167 Achilles tendon Accessory movements in other joints of the foot may contribute up to 20–30% of the total reported range of motion.157 Dorsi- flexion and plantar flexion at the talocrural joint need to be visual- FIG. 14.16 A superior view displays a cross-section through the right ized when the foot is off the ground and free to rotate, and when talocrural joint. The talus remains, but the lateral and medial malleolus the foot is fixed to the ground as the leg rotates forward, such as and all the tendons are cut. during the stance phase of gait.  Chapter 14   Ankle and Foot 605 TABLE 14.3 Selected Full Movements That Stretch the Ligaments of the Ankle* Ligaments Crossed Joints Selected Full Movements That Stretch Ligaments Deltoid ligament (tibiotalar fibers) Talocrural joint Eversion; dorsiflexion with associated posterior slide of talus within the mortise (posterior fibers) { Talocrural joint Eversion, abduction, plantar flexion with associated Deltoid ligament (tibionavicular fibers) anterior slide of talus within the mortise Talonavicular joint Eversion, abduction Deltoid ligament (tibiocalcaneal fibers) Talocrural joint and subtalar joint Eversion Anterior talofibular ligament Talocrural joint Inversion, adduction, plantar flexion with associated anterior slide of talus within the mortise { Talocrural joint Inversion, dorsiflexion with associated posterior slide of Calcaneofibular ligament talus within the mortise Subtalar joint Inversion Posterior talofibular ligament Talocrural joint Abduction, inversion, dorsiflexion with associated posterior slide of talus within the mortise *The information is based on movements of the unloaded foot relative to a stationary leg. Talocrural joint ABDUCTION/ ADDUCTION (Vertical axis) DORSIFLEXION/ EVERSION/ PLANTAR INVERSION FLEXION (AP axis) DORSIFLEXION/ (ML axis) PLANTAR 10 FLEXION 6 (ML axis) A B Posterior view Superior view Neutral PRONATION: Main component SUPINATION: Main component DORSIFLEXION PLANTAR FLEXION C D E FIG. 14.17 The axis of rotation and osteokinematics at the talocrural joint. The slightly oblique axis of rotation (red) is shown from behind (A) and from above (B); this axis is shown again in (C). The component axes and associated osteokinematics are also depicted in (A) and (B). Note that, although subtle, dorsiflexion (D) is combined with slight abduction and eversion, which are components of pronation; plantar flexion (E) is combined with slight adduction and inversion, which are components of supination. 606 Section IV   Lower Extremity DORSIFLEXION Talocrural joint PLANTAR FLEXION Anterior capsule Achilles tendon DO Anterior RS talofibular Anterior IFL ligament Anterior capsule EX DE talofibular Posterior SLI IDE ION SL capsule ligament Posterior capsule ROLL ROLL N IO EX FL R TA AN PL A Calcaneofibular ligament B Calcaneofibular ligament FIG. 14.18 A lateral view depicts the arthrokinematics at the talocrural joint during passive dorsiflexion (A) and plantar flexion (B). Stretched (taut) structures are shown as thin elongated arrows; slackened structures are shown as wavy arrows. Arthrokinematics The following discussion assumes that the foot is unloaded and free to rotate. During dorsiflexion, the talus rolls forward relative to the leg as it simultaneously slides posteriorly (Fig. 14.18A). The simultaneous posterior slide allows the talus to rotate forward with only limited anterior translation.32,197 Fig. 14.18A shows the cal- 0 10 20 30 40 50 60 70 80 90 100 caneofibular ligament becoming taut in response to the posterior sliding tendency of the talus-calcaneal segment. Generally, any 40 collateral ligament that becomes increasingly taut from posterior 30 Ankle joint motion translation of the talus also becomes increasingly taut during dorsi- 20 (degrees) flexion. In addition to the calcaneofibular ligament depicted in Fig. 14.18A, full dorsiflexion also elongates the posterior talofibu- 10 DORSIFLEXION lar ligament and posterior tibiotalar fibers of the deltoid liga- 0 ment.60 Although the magnitude of the resistance produced by −10 PLANTAR the aforementioned collateral ligaments may be relatively small PUSH FLEXION −20 compared with a tissue like the Achilles tendon, in certain clinical OFF situations the tension exerted by collateral ligaments may be abnormally large and may restrict full dorsiflexion. For instance, 0 10 20 30 40 50 60 70 80 90 100 Swing phase Heel contact Foot flat Heel off Toe off full dorsiflexion is often limited following ligament injury or prolonged immobilization of the talocrural joint.7,40,41 One thera- peutic approach aimed at increasing dorsiflexion involves passive joint mobilization of the talocrural joint. Specifically, the clinician Percent of gait cycle applies a posterior-directed translation of the talus and foot relative to the leg.40,75,197 An appropriately applied posterior slide is FIG. 14.19 The range of motion of the right ankle (talocrural) joint is depicted during the major phases of the gait cycle. The push off (propul- designed to stretch all tissues that naturally limit dorsiflexion, sion) phase (about 40% to 60% of the gait cycle) is indicated in the which includes many of the collateral ligaments. The manually darker shade of green. induced posterior slide is also designed to mimic the natural arthrokinematics of dorsiflexion. During plantar flexion, the talus rolls posteriorly as the bone simultaneously slides anteriorly (see Fig. 14.18B). Generally, any Progressive Stabilization of the Talocrural Joint Throughout the collateral ligament that becomes increasingly taut from anterior trans- Stance Phase of Gait lation of the talus also becomes increasingly taut during plantar At initial heel contact during walking, the ankle rapidly plantar flexion. As depicted in Fig. 14.18B, the anterior talofibular liga- flexes in order to lower the foot to the ground (Fig. 14.19; from ment is stretched in full plantar flexion. (Although not depicted, 0% to 5% of the gait cycle). As soon as the foot flat phase of gait the tibionavicular fibers of the deltoid ligament would also become is reached, the leg starts to rotate forward (dorsiflex) over the taut at full plantar flexion [review Table 14.3].) Plantar flexion also grounded foot. Dorsiflexion continues until just after heel off stretches the dorsiflexor muscles and the anterior capsule of the phase. At this point in the gait cycle, the ankle becomes increas- joint. The extremes of plantar flexion can lead to a painful impinge- ingly stable because of the increased tension in many stretched ment between the distal tibia and the posterior talus or calcaneus, collateral ligaments and plantar flexor muscles (Fig. 14.20A). The especially in the presence of an os trigonum (a small and relatively dorsiflexed ankle is further stabilized as the slightly wider anterior rare accessory bone located near the posterior-lateral talus). part of the talus wedges into the tibiofibular component of the  Chapter 14   Ankle and Foot 607 Tibia DO us RS Tal IF LE XI Path of Superior view ON the tibia Achilles tendon Fibula Calcaneofibular B FULL DORSIFLEXION ligament Fibularis longus A FIG. 14.20 Factors that increase the mechanical stability of the fully dorsiflexed talocrural joint are shown. (A) The increased passive tension in several connective tissues and muscles is demonstrated. (B) The trochlear surface of the talus is wider anteriorly than posteriorly (see red line). The path of dorsiflexion places the concave tibiofibular segment of the mortise in contact with the wider anterior dimension of the talus, thereby causing a wedging effect within the talocrural joint. S PE C I A L F O C U S 1 4. 1 Ankle Injury Resulting from the Extremes of Dorsiflexion or Plantar Flexion T he ligaments of the distal tibiofibular joint and the interosse- ous membrane have a close structural relationship with the nearby talocrural joint. This relationship is apparent following an followed closely by the anterior fibers of the deltoid ligament (fibers coursing toward and crossing the talonavicular joint). Strains values of 8–9% were measured in these ligaments—a ankle injury associated with extreme dorsiflexion—for example, stretch theoretically capable of causing injury. resulting from landing from a jump or a fall. Extreme and violent High ankle or syndesmotic sprains are reported to occur in dorsiflexion of the ankle (leg over the foot) can cause the mortise about 10% of all ankle injuries,201 similar to the relative infre- to “explode” outward, injuring several tissues. The traumatic wid- quency of eversion sprains. Because of the likelihood of trauma ening of the mortise and associated displacement of the fibula can to multiple tissues, the recovery time following high ankle sprains injure ligaments of the distal tibiofibular joint as well as interos- often exceeds that required for the more common inversion seous membrane—the so-called high ankle or syndesmotic sprain.117 sprain.201 In combination with extreme dorsiflexion, the mecha- Full plantar flexion—the loose-packed position of the talocrural nism of injury common to many high ankle sprains involves an joint—slackens many collateral ligaments of the ankle and all excessive abduction (external rotation) torque applied to the talus plantar flexor muscles.199 In addition, plantar flexion places the within the mortise. From a weight-bearing perspective, this narrower width of the talus between the malleoli, thereby releas- extreme motion could occur while landing from a jump on the right ing tension within the mortise. As a consequence, full plantar dorsiflexed ankle as the body and lower leg simultaneously rotate flexion causes the distal tibia and fibula to “loosen their grip” on sharply to the left. (Such a motion forcefully internally rotates the the talus. Bearing body weight over a fully plantar flexed ankle, right tibia and fibula relative to the fixed foot.) Often, this stressful therefore, places the talocrural joint in a relatively unstable posi- movement also in