It is situated in the region of ankle. Classification: It is synovial, uniaxial and of the hinge variety. Bones taking part: Lower end of tibia, lower end of fibula and the talus. Lower end of tibia: Lower ends of the tibia and fibula are connected by means of inferior transverse tibio-fibular ligament forming the tibio-fibular mortise. Talus: Upper, lateral and medial aspects of talus present articular areas which are continuous with each other. Articular area on medial side is comma shaped, and the area on lateral side is triangular. Ligaments: (1) Capsular, (2) Anterior ligament, (3) Posterior ligament, (4) Lateral ligament, (5) Medial ligament, and (6) Inferior transverse tibio-fibular ligament. Lateral ligaments are: (1) Anterior talo-fibular ligaments, (2) Posterior talo-fibular ligaments, and (3) the Calcaneo-fibular ligaments. Medial ligament: It is one of the strongest ligaments in the body. It is triangular in shape, hence is known as deltoid ligament. Nerve supply: Ankle joint is supplied by (1) Deep peroneal nerve, (2) Tibial nerve, and (3) Superficial peroneal nerve. Blood supply: Malleolar branches of the anterior tibial and the peroneal arteries supply the joint. Superior tibio-fibular joint: It is a synovial plane variety of joint. Inferior tibio-fibular joint: It is a classical example of syndesmosis (bones are connected by means of ligament alone). Interosseous membrane of leg: It is attached to interosseous borders of the tibia and the fibula. Fibres are directed downwards and laterally from interosseous border of tibia. There is an opening in the upper part of the interosseous membrane meant for the anterior tibial artery. The perforating branch of peroneal artery passes through the opening in the lower part of the interosseous membrane. Joints of foot: Tarsals, metatarsals, and phalanges of toes articulate through the interosseous ligaments, forming the joints of foot. Following Joints Need to be Studied: (1) Joint between calcaneus, and talus (Talocalcanean joint). (2) Talo-calcaneo-navicular joint. (3) Calcaneo \'cuboid joint. (4) Cuneonavicular joint. (5) Cuboideo-navicular joint. (6) Indirect articulation between calcaneus and navicular. (7) Intercuneiform joints. (8) Cuneocuboid joint. (9) Tarsometatarsal joints and intermetatarsal joints. (10) Metatarso-phalangeal joints. (11) Interphalangeal joints. Talocalcanean joint: It is synovial joint. It is also known as sub-talar or sub-taloid articulation. The large posterior calcanean articular facet on the under surface of the body of talus articulates with the similar posterior talar articular facet on the superior aspect of calcaneus. Immediately in front of the respective articular facet lies the sulcus. The sulcus on talus is known as sulcus tali and sulcus on calcaneus is known as sulcus calcani. Articular facet of the calcaneus is convex, while that on talus is concave. Following are ligaments of joint: (1) Medial talocalcanean ligament, (2) Lateral talocalcanean ligament, and (3) Interosseous talocalcanean ligament. Interosseous talocalcanean ligament: It is attached to the groove on talus and the calcaneus in front of articular facets forming the joint. The ligament is arranged into two distinct parts, the medial and lateral. Medial part: It lies in medial part of sinus tarsi and is represented by two lamellae, anterior and posterior. Lateral part: It lies lateral to medial part and is placed in the wider part of the tunnel between talus and calcaneus (Sinus tarsi). It runs between the floor of the groove of calcaneus and the neck of talus. This ligament is known as the cervical ligament. It probably checks the movement of excessive inversion. Talocalcaneonavicular joint: It is synovial and ball and socket type of joint. Proximal component of this joint is formed by rounded head of talus, while distal component is formed by the articular facet of the navicular bone. Talonavicular ligament: It runs from dorsal surface of the neck of talus to dorsal surface of navicular bone. Calcaneo-navicular portion of bifurcated ligament:­ It lies on the lateral aspect of the joint. Bifurcated ligament is Y shaped having medial limb, lateral limb and the stem. Stem is attached to the upper surface of calcaneus to the part not covered by talus. Medial limb runs to dorsi-lateral part of navicular and lateral limb goes to dorsal aspect of cuboid. Movements: Movements of inversion occur at this joint. Indirect articulation between calcaneus and navicular: Anteriorly is attached to the under surface of the navicular and posteriorly to the anterior part of sustentaculum talare (Tali). Ligament support of the head of talus. Deltoid ligament is attached to the spring ligament from above. The tendon of tibialis posterior supports the spring ligament from below. (Deltoid pulls the spring from above and the tibialis posterior supports the spring from below). In the event of rupture of spring ligament, medial longitudinal arch of foot collapses. Tarsometatarsal Joint: Base of first metatarsal articulates with the kidney shaped facet of medial cuneiform bone. Metatarso-phalangeal joints: Heads of metatarsals articulate with concave articular facets on the bases of proximal phalanges. These joints are provided with fibrous capsule and following ligaments: (1) Plantar ligament, (2) Deep transverse metatarsal ligament, and (3) Collateral ligament which runs from tubercle on the side of the head of metatarsal downwards and forwards to the base of proximal phalanx. Deep transverse ligament connects adjoining metatarso-phalangeal joints through plantar metatarso-­phalangeal ligaments. Movements of inversion and eversion: It is due to inversion and eversion we are able to walk on un-even surfaces such as climbing the hill. When the sole of foot tries to face medially and its medial border is raised, it is known as inversion. When sole of the foot tries to face laterally and its lateral border is raised, is known as eversion. Movements associated with inversion and eversion: (1) During inversion, there is adduction of forefoot and plantar flexion of foot. (2) During eversion, there is abduction of the forefoot with the dorsiflexion of the foot. Axis: The axis of inversion and eversion runs upwards, medially and forwards, passing through the body of calcaneus and the neck of talus. Joints involved in movements of inversion and eversion: The movements solely occur at the mid-tarsal and the sub-taloid joints. The rotatary force generated in the midtarsal joint is transmitted to the calcaneus, and it is the calcaneus which rotates under the talus. Mid-tarsal joints are: Calcaneo-cuboid, talo-calcaneo-navicular.