Our patient had inflammation of Kager’s fat pad. Kager’s fat pad is a lipomatous structure located in the posterior ankle joint anterior to the Achilles tendon. On lateral radiographs of the ankle the fat pad is radiolucent and triangular with boundaries formed by the flexor hallucis longus muscle and tendon anteriorly, the superior cortex of the calcaneus inferiorly and the Achilles tendon posteriorly.
What sorts of conditions cause inflammation of the fat pad? Fractures, joint effusions, Achilles tendon injury, arthritis and autoimmune diseases all can cause the fat pad to be opaque on xray. . The most common autoimmune diseases causing this enthesitis ( inflammation where the tendon inserts on the bone) are ankylosing spondylitis and Reiters syndrome. . Reiter’s syndrome( now called 'reactive arthritis" because Reiter experimented in Nazi concentration camps) consists of conjunctivitis, non-gonococcal urethritis and arthritis. It affects the heel in 50% of patients and is often caused by chlamydia. For this reason it has been known as “lover’s heel.” It usually occurs 1-3 weeks after infection and is most commonly associated with Chlamydia.however it can also occur after diarrheal illness with Salmonella, Shigella, or Camphylobacter..
Another cause of inflammation is a retrocalcaneal exostosis called a “pump bump”. This is more common in women and thought to be due to wearing high heeled shoes. This is also called Haglund’s deformity. The cure for this inflammation which leads to the exostosis is to change the height of the heels being worn.
Our patient had conjunctivitis and bilateral heel pain. The formal ultrasound did not show Achilles tendon injury. He was treated for Reiter’s with NSAIDS and antibiotics for Chlamydia.
Ly J, Bui-Mansfield L. Anatomy of and abnormalities associated with Kager’s fat pad. AJR 2004, 182(1).
Pavlov H, Heneghan MA, Hersh A, Goldman AB, Vigorita V. Haglund’s syndrome: intial and differential diagnosis of posterior heel pain. Radiology 1982;144:83-87
Frey C, Rosenberg Z, Shereff MJ, Kim H. The retrocalcaneal bursa: anatomy and burography. Foot Ankle 1992;13:203-207.
McGahan JP, Graves DS, Palmer PES. Coccidioidal spondylitis : usual and unusual radiographic manifestations. AJR 1980;136:5-9.