Bony landmarks
The malleoli are the starting point for every other landmark at the ankle. The medial malleolus, the lower end of the tibia, is broad and sits higher and further forward. The lateral malleolus, the lower end of the fibula, is narrower and reaches lower and further back, which is why the line joining their tips slopes downwards and backwards.
- Head of the talus: felt in front of the ankle, between the malleoli, and easiest to find when the foot is gently inverted and everted.
- Sustentaculum tali: a small ledge about a finger's breadth below the tip of the medial malleolus.
- Navicular tuberosity: the obvious bump on the inner border of the foot in front of and below the medial malleolus. It marks the summit of the medial arch and the insertion of tibialis posterior.
- Fibular trochlea: a small ridge on the lateral calcaneus below the lateral malleolus, separating the two fibular tendons.
- Tuberosity of the fifth metatarsal: the prominence halfway along the outer border of the foot, where fibularis (peroneal) brevis inserts.
- Calcaneal tuberosity: the back of the heel, felt through the thick heel pad.
Tendons you can see and feel
Most tendons at the ankle can be made to stand out by asking for one movement at a time.
| Tendon | Where | How to show it |
|---|---|---|
| Tibialis anterior | Front of the ankle, most medial | Dorsiflex and invert the foot |
| Extensor hallucis longus | Lateral to tibialis anterior, to the great toe | Lift the great toe |
| Extensor digitorum longus | Fans out to the lateral four toes | Lift the toes |
| Tibialis posterior | Behind and below the medial malleolus | Invert the plantarflexed foot |
| Fibularis longus and brevis | Behind and below the lateral malleolus | Evert the foot |
| Calcaneal (Achilles) tendon | Back of the ankle to the heel | Stand on tiptoe |
Extensor digitorum brevis forms a soft, fleshy swelling on the lateral dorsum in front of the lateral malleolus. It is normal and should not be mistaken for oedema or a mass.
Vessels and nerves
Two pulses, two named veins and several cutaneous nerves can be located from surface landmarks alone.
- Dorsalis pedis pulse: on the dorsum, just lateral to the tendon of extensor hallucis longus, pressed against the navicular and intermediate cuneiform.
- Posterior tibial pulse: behind the medial malleolus, roughly midway between it and the calcaneal tendon, felt against the tibia and talus with the foot relaxed.
- Great saphenous vein: runs just in front of the medial malleolus, with the saphenous nerve beside it. This constant position makes it the classic site for a venous cut-down.
- Small saphenous vein and sural nerve: pass behind the lateral malleolus, between it and the calcaneal tendon.
- Superficial fibular nerve: its branches can sometimes be seen under the skin of the anterolateral ankle when the foot is plantarflexed and inverted.
Clinical relevance
Surface landmarks decide who needs an X-ray, where to put a needle and how to test a tendon.
- Ottawa ankle and foot rules: bony tenderness at the posterior edge or tip of either malleolus, at the navicular or at the base of the fifth metatarsal, or an inability to take four steps, means radiographs are needed.
- Simmonds' (Thompson) test: with the patient prone and feet over the couch edge, squeezing a normal calf plantarflexes the foot. No movement suggests a ruptured calcaneal tendon, often with a palpable gap a few centimetres above the heel.
- Ankle joint injection or aspiration: usually anteromedial, just medial to the tendon of tibialis anterior at the joint line, which avoids the dorsalis pedis artery and deep fibular nerve lateral to extensor hallucis longus.
- Foot pulses: both pulses are checked, and an ankle-brachial pressure index is measured over them with a Doppler when they are weak.
- Tibial nerve block: placed next to the posterior tibial pulse behind the medial malleolus.
On the specimen
The station asks for the surface-visible structures on a prosected foot, and the skill is linking the specimen to what you would feel in a patient. The two malleoli are named first and used to side the foot: the lower, more posterior malleolus is lateral.
At the front of the ankle, the thick tendon closest to the medial malleolus is tibialis anterior, the tendon aimed at the great toe is extensor hallucis longus, and the tendon that splits into four is extensor digitorum longus. The muscle belly sitting on the lateral dorsum is extensor digitorum brevis, the same swelling you see on a living foot. Be ready to point on the specimen to where the dorsalis pedis pulse would be felt, lateral to extensor hallucis longus.