The ankle joint forms the connection between the lower leg and the foot and consists of
the upper ankle joint (tibiotalar joint) and the lower ankle joint (subtalar joint), which
together function as a unit. The upper ankle joint is formed by the talus (ankle bone), the
tibia (shinbone), and the fibula (calf bone). Viewed from the front, the tibia with the medial
malleolus and the fibula with the lateral malleolus form the so-called ankle mortise, which
is held together by strong ligaments (syndesmoses). Other important stabilizing ligament
structures include the lateral ligaments and the deltoid ligaments located on the medial
side. Active stabilizers include muscle tendons such as the Achilles tendon, the peroneal
tendons (laterally), and the tibialis anterior tendon (medially). This complex functional unit
can be disrupted by ligament or muscle injuries, leading to painful instability, misalignment,
and cartilage damage.
The most important and most frequently injured ligament due to ankle sprains is the
anterior talofibular ligament (ATFL). If not properly diagnosed, such injuries can lead to
chronic instability with repeated sprains and resulting secondary damage. In most cases,
fresh ligament injuries can be treated non-surgically with braces or splints. However, if
symptomatic instability persists, ligament injuries should be identified early and treated
surgically.
The most common internal damage in the ankle joint is cartilage injury to the talus. Talus
cartilage is particularly thin yet resilient. The so-called "shoulders" of the talus are
especially sensitive and can be damaged by lateral sprains or shear forces from overuse.
Often, the bone beneath the cartilage is also affected, resulting in so-called osteochondral
combination defects. A form of overuse-related damage that can occur during childhood is
known as osteochondritis dissecans.
In early stages of cartilage damage, an arthroscopic procedure is usually sufficient to
remove the damaged tissue and stimulate the bone marrow. During this procedure, the
bone is microfractured to expose its blood-rich layer and release pluripotent stem cells,
which then settle in the defect and form scar-like regenerative tissue. This is sufficient in
most cases to close the defect. For larger osteochondral defects, both bone and cartilage
must be repaired. This can be done with a bone graft (e.g., from the iliac crest) in
combination with cartilage regeneration. For cartilage regeneration, collagen
membranes – with or without the patient´s own cartilage cells – are used.