The ankle-joint is composed of the tibia and fibula above and the astragalus below.

Surface Anatomy

A knowledge of the contour of the ankle aids considerably in determining the character of its diseases and injuries. The malleoli form prominences with distinct hollows above and below them. The sharp anterior edge of the tibia if followed down leads to the tibialis anterior tendon. On the medial (inner) side the malleolus is large and flat. It is subcutaneous and can be readily palpated. At its anterior edge is the commencement of the internal saphenous vein which runs up and slightly back to reach the posterior edge of the tibia 5 to 6 cm. (2 to 2 1/2 in.) above the tip of the malleolus. About 4 cm. (1 1/2 in.) below and in front of the inter-nal malleolus is the prominent tubercle of the scaphoid.

Fig. 566.   Surface anatomy of the outer side of the ankle.

Fig. 566. - Surface anatomy of the outer side of the ankle.

The external malleolus is small and somewhat pointed, and is placed a finger-breadth below and behind the level of the internal malleolus. For a distance of about 7.5 cm. (3 in.) above its tip the fibula is subcutaneous and readily palpated. It is here that it is most often fractured. The transverse line of the joint is level with the upper limit of the swell of the internal malleolus - about 2.5 cm. (1 in.) above the tip of the external malleolus. The ankle is covered in front and behind by tendons, most of which, especially in thin people, can be felt and seen when they are put on the stretch. Anteriorly the innermost tendon is the tibialis anterior, next the extensor longus hallucis, and then the extensor longus digitorum. Sometimes close to the outer side of the extensor of the little (fifth) toe the contraction of the pero-neus tertius tendon can be felt as it goes to be inserted into the fifth metatarsal bone near its base. Running directly downward along the posterior edge of the external malleolus and fibula are the peroneus longus and brevis tendons, the former being the more superficial. About 2.5 cm. (1 in.) below and a little in front of the external malleolus is the peroneal tubercle of the calcaneum; the peroneus brevis passes in front of it to be inserted into the prominent tuberosity of the fifth metatarsal bone. The long tendon passes behind the tubercle, winds around the cuboid, and crosses the sole to insert into the internal cuneiform and base of the first metatarsal bone.

Fig. 567.   Surface anatomy of the inner side of the ankle.

Fig. 567. - Surface anatomy of the inner side of the ankle.

Posteriorly the tendo calcaneus (Achillis) is large and prominent - along the anterior edge of its lateral (external) side run the external (short) saphenous vein and nerve. Running upward from the posterior border of the internal malleolus the tibialis posterior tendon can sometimes be seen and felt. Posterior to it runs the flexor longus digitorum muscle, then the posterior tibial artery, accompanied by venae comites, then the posterior tibial nerve, and lastly the flexor longus hallucis. The artery can be felt pulsating midway between the tendo calcaneus and the internal tuberosity of the calcaneum. The anterior tibial artery can be felt pulsating to the lateral (outer) side of the flexor longus hallucis.