Examining the anatomy of the ankle

Hi all - this is an article I recently wrote for our newsletter:

Depending on what you read, the ankle is a combination of two or three joints.  Some say the ankle is the true ankle joint or talocrural joint and the subtalar joint.  Others include the distal tibiofibular joint in the term "ankle".  If we look at each of these joints in detail we will get a clearer picture of how the ankle moves, where the potential for misalignment lies, and how the "ankle" participates in and/or initiates compensation patterns.

The outlying joint that is an agreed upon part of the "ankle" is the subtalar joint.  The subtalar joint is a combination of two joints:  The talocalcaneal joint and the talocalcaneonavicular joint.  The talus is an irregularly shaped bone that sits on the calcaneus at an oblique angle.  This oblique angle means that the calcaneus articulates with the talus in three distinct places to form these two joints.

The posterior calcaneal articular surface of the talus articulates with the posterior talar articular surface to form the talocalcaneal joint.  While the talocalcaneonavicular joint is formed by three separate articulations:  the middle calcaneal articular surface of the talus articulates with the middle talar articular surface of the calcaneus; and the anterior calcaneal articular surface of the talus articulates with the anterior talar articular surface of the calcaneus and the proximal aspect of the navicular bone (these two articulations are also labeled the acetabulum pedis).

The three articulations and two joints formed between the talus, calcaneus, and navicular bones make up the subtalar joint complex, which is a gliding type joint within the diarthrodial (synovial) group.  Because the subtalar joint complex sits on an oblique angle, its actions occur in all three planes, and in all directions.  The subtalar joint moves into abduction, adduction, plantar flexion, dorsiflexion, eversion, and inversion.

While the subtalar joint complex is highly complex, the other outlying joint sometimes recognized as part of the "ankle" is fairly simple.  It is the distal tibiofibular joint.  The distal tibiofibular joint is an articulation between the distal lateral tibia and the distal medial fibula.  It is a syndesmosis type joint within the synarthrodial group.  It is characterized by the presence of a strong membrane, has no joint capsule, and moves very little.

The distal tibiofibular joint sits just proximal to the true ankle or talocrural joint, which is an articulation between the distal aspect of the tibia, known as the inferior articular surface, and the proximal aspect of the talus, known as the trochlea.  Where these two bones meet is the talocrural joint, which is a hinge joint in the diarthrodial joint group.  Whereas the subtalar joint moves in all three planes, and the distal tibiofibular joint maintains stability, the talocrural joint moves only in a sagittal plane, performing the actions of plantar flexion and dorsiflexion.

The talocrural joint has a ligamentous joint capsule as well as several relatively large ligaments to help it maintain alignment and stability.  The main medial ligament of the talocrural joint is the deltoid ligament.  The deltoid ligament has several portions, these are the posterior tibiotalar, the tibiocalcaneal, the tibionavicular, and the anterior tibiotalar portions.

On the lateral aspect of the talocrural joint there are three main ligaments: the posterior talofibular, the anterior talofibular, and the calcaneofibular ligaments.  The medial and lateral ligaments work together to keep the alignment of the talocrural joint.

There is one more joint that, because of proximity, might be considered part of the "ankle", and that is the talofibular joint.  The talofibular joint is an articulation between the articular facet of the lateral malleolus of the fibula and the lateral articular surface of the talus (in image to the right this is labeled "For lateral malleolus").  Generally, the talofibular joint is not recognized or paid much attention to.  Part of the reason for this may be that the construction of the distal tibiofibular joint holds the distal fibula to the tibia.  This should only let the fibula shift in the same direction as the tibia.  Therefore, there is a much stronger relationship between the tibia and the talus, and any talocrural or talofibular joint misalignment would most likely result from that relationship.

The alignment of the "ankle" is important not only to the proper function and tone in muscle tissue, but also to maintaining healthy ligament tension and preserving the alignment of other joints.  Misalignment at any of the ankle joints can result in compensation within other joints, either in the foot or more proximal in the knee, hip, and sacroiliac joints.  This compensation will create muscle imbalances and tension in connective tissues throughout the leg, thigh, hip, and lower back.