Knee, Leg, and Foot Anatomy

• Knee Joint, Posterior Leg, Lateral Leg, Tarsal Tunnel, Ankle Joint, Foot

Knee Joint Articulations

• Tibiofemoral articulation occurs between the medial/lateral femoral condyles and the medial/lateral tibial plateaus
  • It is a hinge joint
• Patellofemoral articulation is identified between the posterior surface of the patella and patellar surface of the femur
  • It is a plane joint
• Movements include flexion, extension, and some rotation, which is known as the screw home mechanism
• When the knee is extended with the foot planted, it passively "locks" with internal rotation of the femur on the tibia
• The femur must laterally rotate about 5 degrees to “unlock” the knee to produce flexion
• Articular facets on the posterior surface of the patella articulate with the patellar surface of the femur during flexion and extension
• The joint capsule consists of an external fibrous layer (fibrous capsule) and an internal synovial membrane
• The fibrous joint capsule is strengthened by 4 intrinsic and 1 extrinsic ligaments

Intrinsic (Capsular) Ligaments of the Knee

• The patellar ligament (tendon) receives medial and lateral patellar retinacula, maintains alignment of patella, and reinforces joint anteriorly
• The tibial (medial) collateral ligament (MCL) runs from the medial femoral epicondyle to medial tibia and medial meniscus and limits valgus stress
• The arcuate popliteal ligaments are positioned posterior fibular head to the medial side of the knee joint
  • Supports the posterolateral knee, and prevents hyperextension
• The oblique popliteal ligament is an expansion of the semimembranosus tendon and strengthens the capsule posteriorly

Extrinsic (Extracapsular) Ligaments of the Knee

• The fibular (lateral) collateral ligament (LCL) runs from the lateral femoral condyle to fibular head and limits varus stress

Intraarticular Ligaments of the Knee

• The anterior cruciate ligament (ACL) runs from the anterior intercondylar eminence of tibia extending posterolaterally to the posterior part of the medial surface of the lateral femoral condyle and limits posterior displacement of femur on tibia OR anterior displacement of tibia on the femur/hyperextension
• The posterior cruciate ligament (PCL) runs from the posterior intercondylar eminence of tibia extending anteromedially to the anterior part of the lateral surface of the medial femoral condyle and limits posterior displacement of tibia on femur OR anterior displacement of femur on tibia, and it prevents hyperflexion

Other Support Structures of the Knee

• Iliotibial band
• Pes Anserine
• Menisci (crescent): Fibrocartilage on the articular surface of tibia that deepens the articular surface.
  • It provides shock absorption, and it is thicker at external margins, tapering to thin
  • Coronary ligaments attach the menisci to the edge of the tibial plateau\
  • The transverse ligament connects the anterior surface of the medial and lateral menisci across the intercondylar space

Medial and Lateral Meniscus of the Knee

• The medial meniscus is C-shaped, attached to the intercondylar space anterior and posteriorly, attached to the MCL, and is less mobile
• The lateral meniscus is smaller and circular, attached to the popliteus tendon posteriorly, attached to the medial condyle of the femur posteriorly through the posterior meniscofemoral ligament, and exhibits minimal attachments, making it more mobile

Bursa of the Knee

• Bursa decreases friction
• Four bursae are continuous with the synovial cavity:
  • Suprapatellar is located between the femur and quadriceps tendon\
  • Pes Anserine is deep to tendons of pes anserine
  • Popliteus is between the tendon of the popliteus and the lateral tibial condyle
  • Gastrocnemius is deep to the medial head of the gastroc
• Prepatellar bursa is located between the patella and the skin
• Infrapatellar bursa is located between the patellar ligament and tibia

Muscles of the Posterior Compartment of the Leg

• Superficial (gastric + soleus = triceps surae) includes:
  • Gastrocnemius
  • Soleus
  • Plantaris
• Deep includes:
  • Popliteus
  • Tibialis posterior (Tom)
  • Flexor digitorum longus (Dick)
  • Flexor hallucis longus (Harry)

Arteries of the Posterior Compartment

• Popliteal Artery
  • A continuation of the femoral artery as it emerges from the adductor hiatus
  • Ends by dividing into anterior and posterior tibial arteries at the inferior border of popliteus
• Posterior Tibial Artery
  • Terminal branch of the popliteal artery
  • Supplies the posterior compartment of the leg and foot
• Fibular (Peroneal) Artery
  • Branch of the posterior tibial artery in the posterior compartment
  • Supplies the lateral compartment

Veins of the Posterior Compartment

• Superficial
  • Small (lesser) saphenous vein runs from the foot to the popliteal vein along the posterior calf
• Deep
  • Posterior tibial and fibular (peroneal) veins drain from the foot and flow into the popliteal vein
  • Popliteal vein drains the calf and lateral leg and flows into the femoral vein

Nerves of the Posterior Compartment

• Tibial Nerve
  • Larger terminal branch of the sciatic nerve
  • Has 2 cutaneous branches, the sural and medial calcaneal nerves
  • Runs between the flexor hallucis longus and flexor digitorum longus at the ankle
  • Divides into the medial and lateral plantar nerves
• Common Fibular (Peroneal) Nerve
  • Smaller terminal branch of the sciatic nerve
  • Leaves the popliteal fossa superior to the lateral head of the gastrocnemius
  • Divides into superficial and deep fibular (peroneal) nerves

Lateral Compartment of the Leg

• Fibularis (Peroneus) Longus
• Fibularis (Peroneus) Brevis

Tarsal Tunnel

• Formed by the medial malleolus, medial and posterior surfaces of the talus, and medial surface of calcaneus
• Contents include:
  • Tibialis Posterior Tendon
  • Flexor Digitorum Longus Tendon
  • Posterior Tibial Artery & Vein
  • Tibial Nerve
  • Flexor Hallucis Longus Tendon
• Covered by the flexor retinaculum spanning the tip of the medial malleolus and calcaneus

Tibiofibular Joints

• Superior Tibiofibular Joint
  • Plane joint between the fibular head and the lateral tibial condyle
  • Ligaments include the joint capsule, and anterior and posterior ligaments of the fibular head
  • Exhibits slight glides following ankle joint movements
• Inferior Tibiofibular Joint (Tibiofibular Syndesmosis)
  • Fibrous, syndesmosis joint between the shafts and distal ends of the tibia and fibula
  • Ligaments include the interosseous membrane, anterior and posterior tibiofibular ligaments, and the inferior transverse ligament (forms the posterior wall of ankle mortise)
  • Exhibits slight glides following ankle joint movements

Ankle (Talocrural) Joint

• Hinge joint between the distal ends of the tibia and fibula (ankle mortise) and the superior part of the talus
  • The tibiotalar articulation is the weightbearing surface
• Ligaments include the joint capsule, lateral (fibular) collateral ligaments, and medial (deltoid) ligament

Collateral Ligaments of the Ankle

• Lateral (fibular) collateral ligaments stabilize the joint during inversion, limiting adduction
  • Anterior talofibular ligament (ATFL) is a flat, weak band from malleolus to the neck of the talus
  • Posterior talofibular ligament is a thick, strong band from malleolar fossa to the lateral tubercle of the talus
  • Calcaneofibular ligament is a round cord from the lateral malleolus to the lateral calcaneus
• The medial ligament of the ankle (deltoid ligament) stabilizes the joint in eversion, limiting abduction
  • Fans out from the medial malleolus to distal talus, calcaneus, and navicular and stabilizes during eversion, preventing subluxation of the joint
• Movement includes dorsiflexion and plantarflexion
  • The talus is wider anteriorly, so the tibia and fibula must spread apart to accommodate during dorsiflexion

Subtalar Joint

• Plane synovial joint between the inferior surface of the talus and the superior surface of the calcaneus
• Ligaments include the fibrous joint capsule, medial/lateral/posterior talocalcaneal ligaments (support the capsule), and the interosseous talocalcaneal ligament (binds bones together)
• Movement includes eversion and inversion of the foot

Transverse Tarsal Joint

• Consists of the calcaneocuboid and talocalcaneonavicular joints

Calcaneocuboid and Talocalcaneonavicular Joints

• Calcaneocuboid
  • Articulation: Anterior calcaneus with posterior surface of cuboid
  • Ligaments: Fibrous capsule, dorsal and plantar calcaneocuboid ligament (short plantar ligament), and the long plantar ligament
• Talocalcaneonavicular
  • Articulation: Anterior and medial calcaneus and posterior aspect of navicular with the head of the talus
  • Ligaments: Fibrous capsule and spring ligament (plantar calcaneonavicular ligament)
    • Triangular band extending from sustentaculum tali to posteroinferior surface of navicular bone, blends with deltoid ligament medially, and plays an important role in maintaining the longitudinal arch of the foot
• Movements: Accentuate the motions of the subtalar joint

Tarsometatarsal Joints

• Plane synovial joint between the anterior aspect of tarsal bones with the base of metatarsal bones
• Ligaments: Separate capsules for each joint
• Movements: glides or slides

Metatarsophalangeal Joint (MTP)

• Condyloid synovial joint between the head of metatarsals and the base of proximal phalanges
• Ligaments: Separate capsules for each joint, medial and lateral collateral ligaments, plantar ligaments, and the deep transverse metatarsal ligament which links metatarsal heads
• Movements: Flexion/extension, abduction/adduction

Interphalangeal Joints

• Hinge synovial joint between the head of one phalanx and the base of the phalanx distal to it
• Ligaments: Separate joint capsules for each joint, medial and lateral collateral ligaments, and plantar ligaments
• Movements: flexion/extension

Arches of the Foot

• Bones of the foot are arranged in a transverse and 2 longitudinal arches
• Important for shock absorption, supporting body weight, and propulsion of movement

Longitudinal Arches of the Foot

• Medial longitudinal arch is high and important
  • Consists of: Calcaneus, talus, navicular, 3 cuneiform, and 3 metatarsals
• Lateral longitudinal arch is flatter and rests on the ground during standing.\
  • Consists of: Calcaneus, cuboid, and lateral 2 metatarsals
• Transverse Arch
  • Created by the cuneiforms, cuboid, and bases of the metatarsals
• The bony arches are maintained by passive and dynamic factors

Passive and Dynamic Factors

• Passive
  • Shape of the united bones
  • Four layers of fibrous tissue (superficial to deep)
    • Plantar aponeurosis, long plantar ligament, short plantar ligament (plantar calcaneocuboid), and the spring ligament (plantar calcaneonavicular)
• Dynamic
  • Reflexive bracing action of intrinsic muscles of the foot
  • Contractions of muscles with long tendons extending to the foot
    • Tibialis posterior, flexor digitorum longus, flexor hallucis longus, fibularis longus, and tibialis anterior

Functional Zones of the Foot

• Hindfoot: consists of the talus and calcaneus
• Midfoot: consists of the navicular, cuboid, and cuneiforms
• Forefoot: consists of the metatarsals and phalanges

Plantar Aponeurosis

• Thickening of the deep fascia on the plantar aspect of the foot
  • Anchored to the calcaneal tuberosity posteriorly
• Longitudinal bands of dense fibrous connective tissue extend toward digits
  • Divides into 5 bands to enclose digital tendons
• Extends laterally to form the superficial transverse metatarsal ligaments
• Supports the longitudinal arches and protects deeper structures of the sole of the foot

Fibrous Digital Sheaths and Dorsal Expansion Hoods

• Similar to hands
• Flexor digitorum longus and flexor digitorum brevis, and flexor hallucis longus, tendons are enclosed in fibrous digital sheaths.
  • Acts like tunnels on the plantar aspect of digits
• Triangular-shaped fibrous expansions over the dorsal aspect of the MTP and extending to the apex of the digits
  • Tendons of extensor digitorum longus, extensor digitorum brevis, extensor hallucis longus pass into the extensor expansions

Intrinsic Muscles of the Foot

• 2 originate on the dorsum of the foot
  • Extensor Digitorum Brevis and Extensor Hallucis Brevis
• All others are on the plantar aspect and organize into 4 layers:
  • Layer 1: Abductor Hallucis, Flexor Digitorum Brevis, Abductor Digiti Minimi
  • Layer 2: Quadratus Plantae, Lumbricals
  • Layer 3: Flexor Hallucis Brevis, Adductor Hallucis, Flexor Digiti Minimi Brevis
  • Layer 4: Dorsal and Plantar Interossei

Arteries of the Foot

• Dorsum
  • Dorsalis Pedis Artery
    • Continuation of anterior tibial artery and forms the deep plantar arch with the lateral plantar artery
• Sole
  • Medial Plantar Artery
    • Branch of the posterior tibial artery
  • Lateral Plantar Artery
    • Branch of the posterior tibial artery and forms the deep plantar arch with the dorsalis pedis artery

Veins of the Foot

• Superficial
  • Dorsal venous network drains into the great saphenous vein
  • Plantar venous network drains into the small saphenous vein
• Deep
  • Plantar venous arch drains to the posterior tibial and fibular veins
  • Posterior tibial and fibular veins accompany their named arteries

Nerves of the Foot

• Tibial N.
  • Divides into medial and lateral plantar nerves

Medial and Lateral Plantar Nerves

• Medial Plantar N. (Tibial N.)
  • Sensory: Plantar aspect of the medial foot and 3.5 digits and sides/dorsums of them
  • Motor: Abd Hallucis, Flexor Digitorum Brevis, Flexor Hallucis Brevis, 1st Lumbrical
• Lateral Plantar N. (Tibial N.)
  • Sensory: Plantar aspect of the lateral foot and lateral 1.5 digits as well as the distal dorsal aspects of those digits
  • Motor: Quadratus plantae, abductor digiti minimi, flexor digiti minimi brevis, plantar and dorsal interossei, Lumbricals 2-4, Adductor Hallucis
• Common Fibular N.
  • Divides into deep & superficial fibular nerves
• Deep Fibular N.
  • Sensory: Skin of the first webspace including the proximal dorsums of digits 1 and 2
    • Motor: Extensor Digitorum Brevis, Extensor Hallucis Brevis
• Superficial Fibular (Common Fibular N.)
  • Skin on the dorsum of foot and proximal dorsal aspects of all digits, except lateral side of 5th digit and 1st web space
• Sural N. (cutaneous branches of Tibial and Common Fibular N.s)
  • Skin of the lateral hindfoot, midfoot, and 5th digit
• Calcaneal Branches of Tibial and Sural Ns.
  • Skin of the heel of the foot
• Saphenous N. (Femoral N. in the femoral triangle)
  • Skin of the medial side of the proximal foot to the head of 1st metatarsal

Clinical Pearls

• Cruciate Ligament Injury/Testing
• Knee Arthroplasty
• Ankle Arthroplasty
• Pes Planus
• Plantar Fasciitis