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Posterior Ankle Bursa

bursa tendinis calcanei posterior

The posterior ankle bursa (pre-Achilles bursa or retrocalcaneal bursa is sometimes conflated, but the posterior ankle bursa specifically refers to the adventitial bursa in Kager's fat pad region between the posterior tibial structures and the posterior ankle capsule). The Kager's fat pad itself is the triangular adipose tissue in the posterior ankle space bounded by the FHL muscle anteriorly, the Achilles tendon posteriorly, and the calcaneus inferiorly. Inflammation within this fat pad (Hoffa-equivalent posterior ankle) produces posterior ankle impingement.

Region: Foot & Ankle

Clinical Relevance

Clinical Notes

Posterior ankle impingement from Haglund deformity (prominent superior calcaneal posterosuperior tuberosity), os trigonum, or posterior talar process produces pain at the posterior ankle during plantarflexion. The Kager's fat pad is compressed during plantarflexion and its MRI signal change (oedema) indicates posterior ankle impingement. Arthroscopic posterior ankle surgery decompresses the posterior ankle space including the os trigonum, the Haglund deformity, and the Kager's fat pad impingement through posteromedial and posterolateral portals.

Pathology

Common Injuries & Conditions

Posterior Ankle Impingement with Kager's Fat Pad Oedema

Ballet dancer's posterior ankle impingement in the demi-pointe position compresses the Kager's fat pad between the posterior calcaneus, os trigonum, and Achilles tendon producing posterior ankle pain and fat pad oedema on MRI; arthroscopic posterior ankle decompression removes the os trigonum and reduces the posterior tuberosity to relieve the impingement.