For the clinician and operator an exact knowledge of surface anatomy is absolutely essential. It can readily be acquired because the various bony points and tendons are usually evident both to touch and sight. Bony Landmarks. - There are five prominent bony points: they are the internal and external malleoli, the tubercles of the os calcis and navicular (scaphoid) and the tuberosity of the fifth metatarsal bone.

The internal malleolus is large and flat and has a somewhat rounded lower edge. It is above and anterior to the external malleolus. Immediately in front of its anterior edge runs the commencement of the long saphenous vein. Around its lower posterior border runs the tendon of the tibialis posterior muscle on its way to the tubercle of the scaphoid.

Fig. 588.   The foot in an abducted or pronated position.

Fig. 588. - The foot in an abducted or pronated position.

The external malleolus is more prominent than the internal, smaller, and more pointed. The fibula above for its lower fourth is subcutaneous. The tip of the external malleolus is 2 cm. (3/4 in.) below and behind the internal. Around its posterior and lower edge run the peroneus longus and brevis tendons.

The tubercles of the os calcis can be felt posteriorly and at the sides. The external surface can be followed forward, but the internal is buried beneath the soft tissues. Of the two tubercles on its under surface the internal can be felt by firm pressure.

The tubercle of the scaphoid {navicular) lies on the plantar rather than on the lateral aspect of the bone. It can be felt 4 cm. (1 1/2 in.) below and in front of the internal malleolus. It is the landmark for the tarsal joints on the inner side of the foot. The tibialis posterior muscle runs from it to the posterior edge of the internal malleolus.

Fig. 589.   Surface anatomy of the inner side of the ankle.

Fig. 589. - Surface anatomy of the inner side of the ankle.

The sustentaculum tali can be found by feeling 2.5 cm. (1 in.) below the internal malleolus. It is not very distinct.

The tuberosity of the fifth metatarsal bone is the large bony prominence 6 cm. (2 1/2 in.) below and in front of the external malleolus. It is the guide to the tarsal joints on the outside of the foot. The tendon of the peroneus brevis runs from it to the posterior edge of the external malleolus.

Fig. 590.   Surface anatomy of the outer side of the ankle.

Fig. 590. - Surface anatomy of the outer side of the ankle.

The peroneal spine (tubercle) can be felt indistinctly as a small bony prominence 2.5 cm. (1 in.) below and a little in front of the external malleolus. In front of it runs the peroneus brevis and behind it the peroneus longus.