Calcaneal abnormalities in articular disorders. Rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, and Reiter syndrome.

The calcaneus of normal control patients, and those with rheumatoid arthritis, ankylosing spondylitis, psoriasis, and Reiter syndrome was studied. Pathological abnormalities of the plantar aponeurosis, Achilles tendon, and retrocalcaneal bursa account for the radiographic alterations. In normal individuals, lateral radiographs show the thickness of the Achilles tendon to be not greater than 8 mm; the retrocalcaneal bursa creates a radiolucency which extends at least 2 mm below the superior surface of the calcaneus. In patients with any of these 4 articular disorders, Achilles tendinitis produces thickening of the tendon, and retrocalcaneal bursitis obliterates the normal radiolucency.