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The ankle joint (Fig. 50.1)
tendocalcaneus inserts; a smooth upper part which is separated from
• Type: the ankle is a synovial hinge joint involving the tibia, fibula
the tendocalcaneus by a bursa (retrocalcaneal bursa) (Fig. 50.4); and a
and talus. The articular surfaces are covered with cartilage and synovial
lower part which is covered by a fibro-fatty pad that forms the heel.
membrane lines the rest of the joint. posterior surface has three areas: a roughened middle part where the
• Capsule: the capsule encloses the articular surfaces. The capsule is Medial and lateral tubercles are present on the inferior surface to which
reinforced on either side by strong collateral ligaments but is lax anter- the plantar aponeurosis is attached. The sustentaculum tali is a distinct-
iorly to permit uninhibited hinged movement. ive projection on the medial surface which forms a shelf for the support
• Ligaments: the medial collateral (deltoid) ligament consists of a of the talus. The peroneal tubercle, a small projection on the lateral sur-
deep component which is a vertical band passing from the medial face of the calcaneus, separates the tendons of peroneus longus and
malleolus to the talus. The superficial component of this ligament is fan brevis. The anterior surface has a facet for articulation with the cuboid.
shaped and extends from the medial malleolus to (from front to back): • Cuboid: has a grooved undersurface for the tendon of peroneus
the tuberosity of the navicular, the spring ligament (see below), the sus- longus.
tentaculum tali and the posterior tubercle of the talus (Figs 50.1 and 50.4). • Navicular: has facets for the articulations with the head of the talus
The lateral collateral ligament consists of three bands: the anterior posteriorly and the three cuneiforms anteriorly. It has a tuberosity on its
and posterior talofibular ligaments and the calcaneofibular ligament medial aspect which provides attachment for tibialis posterior.
(Fig. 50.3). Abduction/adduction forces on the ankle can cause a • Cuneiforms: there are three cuneiforms which articulate anteriorly
sprainaan incomplete tear of one of the collateral ligaments. Complete with the metatarsals and posteriorly with the navicular. Their wedge-
tears of the ligaments also occur and lead to painful instability at the shape helps to maintain the transverse arch of the foot.
ankle joint on clinical examination. Severe forces on the ankle joint can • Metatarsals and phalanges: these are similar to the metacarpals and
result in fracture or fracture dislocation. phalanges of the hand. Note the articulations of the heads of the
metatarsals. The 1st metatarsal is large and is important for balance.
The movements at the ankle The head is grooved on its inferior surface for the two sesamoid bones
It is important to note that the inversion and eversion movements of within the tendon of flexor hallucis brevis.
the foot do not occur at the ankle joint except in full plantarflexion.
These occur at the subtalar and midtarsal joints (see below). Only The foot joints
dorsiflexion (extension) and plantarflexion (flexion) occur at the ankle. • Subtalar joint (Fig. 50.2): this compound joint comprises the talo-
The principal muscles are: calcaneal and the talocalcaneonavicular joints. Inversion and eversion
• Dorsiflexion: tibialis anterior and to a lesser extent extensor hallucis movements occur at the subtalar joint.
longus and extensor digitorum longus. • The talcocalcaneal jointais a synovial plane joint formed by the
• Plantarflexion: gastrocnemius and soleus and to a lesser extent articulation of the upper surface of the calcaneus with the lower
tibialis posterior, flexor hallucis longus and flexor digitorum longus. surface of the talus.
• The talocalcaneonavicular jointais a synovial ball and socket
The foot bones (Fig. 50.2) joint between the head of the talus and the sustentaculum tali, the
With the exception of the metatarsals and phalanges the foot bones are spring ligament and the navicular.
termed collectively the tarsal bones. • Midtarsal joint (Fig. 50.2): is also a compound joint which con-
• Talus: has a body with facets on the superior, medial and lateral sur- tributes towards foot inversion/eversion movements. This joint is com-
faces for articulation with the tibia, medial malleolus and lateral malle- posed of the calcaneocuboid joint and the talonavicular component of
olus, respectively. There is a groove on the posterior surface of the the talocalcaneonavicular joint.
body for the tendon of flexor hallucis longus. To the groove’s lateral • The calcaneocuboid jointais a synovial plane joint formed
side is the posterior (lateral) tubercle, sometimes known as the os between the anterior surface of the calcaneus and the posterior
trigonum, as it ossifies from a separate centre to the talus. A head pro- surface of the cuboid.
jects distally which articulates with the navicular. The head is con- • Other foot joints (Fig. 50.2): these include other tarsal joints, tar-
nected to the body by a neck. sometatarsal (synovial plane), intermetatarsal (synovial plane), meta-
• Calcaneus: has two facets on the superior surface which participate tarsophalangeal (synovial condyloid) and interphalangeal (synovial
in the subtalar (talocalcaneal and talocalcaneonavicular) joint. The hinge) joints.

The ankle and foot I 115