The osteology of the ankle joint comprises three bones and three articulations. The tibia and the fibula both articulate at their distal ends with the talus, making the true ankle articulation. On the proximal part, there is a tiny surface connection between fibula and tibia, the so called syndesmosis that is extending from the articular surface of the distal fibula (i.e., lateral malleolus), including a small synovial recess. This explains why synovial joint fluid might extend into a completely normal syndesmosis. Lateral malleolus extents 1 cm more distal than the medial malleolus, the distal part of the tibia. This medial malleolus consists of two colliculi separated by a groove. The ventral colliculus extends 0.5 cm farther then the posterior colliculus. The third malleolus is the prominence of the distal tibia, known as posterior malleolus or malleolus tertius. The tibia and fibula are tightly bound, constituting a fork: medial malleolus, tibial plafond and lateral malleolus cover the talus on three sides. This is known as the “mortise” configuration. So the talus is intercalated, no tendons attach. Talus is cylindrical with more convexity in the a-p direction. Trochlea of talus is more wide anterior than posterior. This morphology leads to movements of talus in the mortise of 20 degree dorsiflexion and 50 degree of plantar flexion.

This intercalated talar bone firmly is attached to tibia, fibula and calcaneus by ligamentous network. On the medial side there is the important deltoid ligament, consisting of a deep layer connecting tibia with posteromedial talus. More superficial the deltoid comprises of less strong components making connection with navicular, spring ligament and calcaneus. On the lateral side tibia and fibula connect anterior to posterior with anterior tibiofibular ligament (ATiFL), interosseous membrane and the posterior tibiofibular ligament (PTiFL): together the syndesmotic complex. Posterior tibiofibular ligament is considered a posterior labrum, with two separate components superior band and deep transverse band. Final ligaments on the lateral side attach the fibula to the talus, with anterior (ATFL) and posterior (PTFL) talofibular ligament and to the calcaneus with the calcaneofibular ligament (CFL).

Extra articular structures that are of interest to us as radiologists are muscles and more specifically accompanying tendons (Fig. 1). Following the anatomy anteriorly we find from medial to lateral the tendons Tibialis anterior, the Extensor Hallucis and the Extensor Digitorum (Tom Hates Dick) tendon. Originating posterior and extending into the medial aspect of the ankle we encounter from anterior to posterior the tendons of the Tibialis Posterior, Flexor Digitorum, Flexor Hallucis Longus (Tom Dick and Harry). It is important to recognize that these tendon originate posteriorly, implying that posterior ankle pain can easily be caused by them. Posterior we encounter the Achilles tendon, a tendon that lies far back from the ankle joint, yet cause of severe posterior ankle pain. The Achilles tendon is anatomically different from the other tendon around the ankle for the absence of a tendon sheet, instead it is enveloped within a tiny highly permeable peritendinium. The lateral compartment comprises the peroneal tendons, peroneal Longus on the outside and the peroneal brevis on the inside. From an anatomical point of view this side of the ankle hosts anatomical variations quite often with additional peroneal muscles and tendons.

From a patients perspective the above mentioned anatomical separation is quite irrelevant. The patient almost always presents itself with a specific location of the ankle problem. This may be extremely obvious, such as inversion injury with immediate lateral ankle pain, or less obvious, such as an inversion injury with late posteromedial ankle pain or deep ankle pain. After a careful anamnesis and clinical assessment the referring medical specialist might know the anatomical structure that is suspected of pathology, yet quite often the request for MR lists a suggested Differential Diagnosis. We, as reading radiologists might feel the need to clear all mentioned anatomical structures. In my opinion the knowledge of the several pathological entities, distributed by their anatomical location, is more helpful in arriving at the right diagnosis.

I choose to focus the pathology section on some pathological entities that are frequently seen in our tertiary referral center for ankle and sports pathology.