Ankle Joint Anatomy PDF

**Ankle joint** The ankle joint is synovial in type and involves the talus of the foot and the tibia and fibula of the leg ( [Fig. 6.104](https://www-clinicalkey-com.utrechtuniversity.idm.oclc.org/f0525) ). Fig. 6.104 Ankle Joint. ( **A **) Anterior view with right foot plantarflexed. ( **B **) S...

**Ankle joint** The ankle joint is synovial in type and involves the talus of the foot and the tibia and fibula of the leg ( [Fig. 6.104](https://www-clinicalkey-com.utrechtuniversity.idm.oclc.org/f0525) ). Fig. 6.104 Ankle Joint. ( **A **) Anterior view with right foot plantarflexed. ( **B **) Schematic of joint, posterior view. ( **C **) Superior view of the talus to show the shape of the articular surface. The ankle joint mainly allows hinge-like dorsiflexion and plantarflexion of the foot on the leg. The distal end of the fibula is firmly anchored to the larger distal end of the tibia by strong ligaments. Together, the fibula and tibia create a deep bracket-shaped socket for the upper expanded part of the body of the talus: - The roof of the socket is formed by the inferior surface of the distal end of the tibia. - The medial side of the socket is formed by the medial malleolus of the tibia. - The longer lateral side of the socket is formed by the lateral malleolus of the fibula. The articular surfaces are covered by hyaline cartilage. The articular part of the talus is shaped like a short half-cylinder tipped onto its flat side with one end facing lateral and the other end facing medial. The curved upper surface of the half-cylinder and the two ends are covered by hyaline cartilage and fit into the bracket-shaped socket formed by the distal ends of the tibia and fibula. When viewed from above, the articular surface of the talus is much wider anteriorly than it is posteriorly. As a result, the bone fits tighter into its socket when the foot is dorsiflexed and the wider surface of the talus moves into the ankle joint than when the foot is plantarflexed and the narrower part of the talus is in the joint. The joint is therefore most stable when the foot is dorsiflexed. The articular cavity is enclosed by a synovial membrane, which attaches around the margins of the articular surfaces, and by a fibrous membrane, which covers the synovial membrane and is also attached to the adjacent bones. **In the clinic: Fracture of the talus** The talus is an unusual bone because it ossifies from a single primary ossification center, which initially appears in the neck. The posterior aspect of the talus appears to ossify last, normally after puberty. In up to 50% of people there is a small accessory ossicle (the os trigonum) posterior to the lateral tubercle of the posterior process. Articular cartilage covers approximately 60% of the talar surface and there are no direct tendon or muscle attachments to the bone. One of the problems with fractures of the talus is that the blood supply to the bone is vulnerable to damage. The main blood supply to the bone enters the talus through the tarsal sinus from a branch of the posterior tibial artery. This vessel supplies most of the neck and the body of the talus. Branches of the dorsalis pedis artery enter the superior aspect of the talar neck and supply the dorsal portion of the head and neck, and branches from the fibular artery supply a small portion of the lateral talus. Fractures of the neck of the talus often interrupt the blood supply to the talus, so making the body and posterior aspect of the talus susceptible to osteonecrosis, which may in turn lead to premature osteoarthritis and require extensive surgery. The ankle joint is stabilized by **medial** (deltoid) and **lateral ligaments** . **Medial ligament (deltoid ligament)** The medial (deltoid) ligament is large, strong ( [Fig. 6.105](https://www-clinicalkey-com.utrechtuniversity.idm.oclc.org/f0530) ), and triangular in shape. Its apex is attached above to the medial malleolus and its broad base is attached below to a line that extends from the tuberosity of the navicular bone in front to the medial tubercle of the talus behind. Fig. 6.105 Medial Ligament of the Ankle Joint, Right Foot. The medial ligament is subdivided into four parts based on the inferior points of attachment: - The part that attaches in front to the tuberosity of the navicular and the associated margin of the plantar calcaneonavicular ligament (spring ligament), which connects the navicular bone to the sustentaculum tali of the calcaneus bone behind, is the **tibionavicular part **of the medial ligament. - The **tibiocalcaneal part**, which is more central, attaches to the sustentaculum tali of the calcaneus bone. - The **posterior tibiotalar part **attaches to the medial side and medial tubercle of the talus. - The fourth part (the **anterior tibiotalar part **) is deep to the tibionavicular and tibiocalcaneal parts of the medial ligament and attaches to the medial surface of the talus. **Lateral ligament** The lateral ligament of the ankle is composed of three separate ligaments, the anterior talofibular ligament, the posterior talofibular ligament, and the calcaneofibular ligament ( [Fig. 6.106](https://www-clinicalkey-com.utrechtuniversity.idm.oclc.org/f0535) ): - The **anterior talofibular ligament **is a short ligament, and attaches the anterior margin of the lateral malleolus to the adjacent region of the talus. - The **posterior talofibular ligament **runs horizontally backward and medially from the malleolar fossa on the medial side of the lateral malleolus to the posterior process of the talus. - The **calcaneofibular ligament **is attached above to the malleolar fossa on the posteromedial side of the lateral malleolus and passes posteroinferiorly to attach below to a tubercle on the lateral surface of the calcaneus. Fig. 6.106 Lateral Ligament of the Ankle Joint. (**A**) Lateral view, right foot. (**B**) Posterior view, right foot. **Intertarsal joints** The numerous synovial joints between the individual tarsal bones mainly invert, evert, supinate, and pronate the foot: - Inversion and eversion is turning the whole sole of the foot inward and outward, respectively. - Pronation is rotating the front of the foot laterally relative to the back of the foot, and supination is the reverse movement. Pronation and supination allow the foot to maintain normal contact with the ground when in different stances or when standing on irregular surfaces. The major joints at which movements occur include the subtalar, talocalcaneonavicular, and calcaneocuboid joints ( [Fig. 6.107](https://www-clinicalkey-com.utrechtuniversity.idm.oclc.org/f0540) ). The talocalcaneonavicular and calcaneocuboid joints together form what is often referred to as the **transverse tarsal joint**.  Fig. 6.107 Intertarsal Joints, Right Foot. Intertarsal joints between the cuneiforms and between the cuneiforms and the navicular allow only limited movement. The joint between the cuboid and navicular is normally fibrous. **\ ** **In the clinic: Ankle fractures** An appreciation of ankle anatomy is essential to understand the wide variety of fractures that may occur at and around the ankle joint. The ankle joint and related structures can be regarded as a fibro-osseous ring oriented in the coronal plane. - The upper part of the ring is formed by the joint between the distal ends of the fibula and tibia and by the ankle joint itself. - The sides of the ring are formed by the ligaments that connect the medial malleolus and lateral malleolus to the adjacent tarsal bones. - The bottom of the ring is not part of the ankle joint, but consists of the subtalar joint and the associated ligaments. Visualizing the ankle joint and surrounding structures as a fibro-osseous ring allows the physician to predict the type of damage likely to result from a particular type of injury. For example, an inversion injury may fracture the medial malleolus and tear ligaments anchoring the lateral malleolus to the tarsal bones. The ring may be disrupted not only by damage to the bones (which produces fractures) but also by damage to the ligaments. Unlike bone fractures, damage to ligaments is unlikely to be appreciated on plain radiographs. When a fracture is noted on a plain radiograph, the physician must always be aware that there may also be appreciable ligamentous disruption. Ottawa Ankle Rules The Ottawa ankle rules were developed to assist clinicians in deciding whether patients with acute ankle injuries require investigation with radiographs in order to avoid unnecessary studies. Named after the hospital where they were developed, the rules are highly sensitive and have reduced the utilization of unwarranted ankle radiographs since their implementation. An ankle X-ray series is required if there is ankle pain and any of the following: - Bone tenderness along the distal 6 cm of the posterior tibia or tip of the medial malleolus - Bone tenderness along the distal 6 cm of the posterior fibula or tip of the lateral malleolus - Inability to bear weight for four steps both immediately after the injury and in the emergency department A foot X-ray series is required if there is midfoot pain and any of the following: - Bone tenderness at the base of the fifth metatarsal bone - Bone tenderness at the navicular bone - Inability to bear weight for four steps both immediately after the injury and in the emergency department