Tendon calcifications in chondrocalcinosis. A clinical, radiologic, histologic, and crystallographic study.

Fine linear extraarticular calcium deposits were found in X-rays of 7 of 52 patients with articular chondrocalcinosis (ACC). Seven Achilles tendons, seven quadriceps tendons, and one plantar fascia were affected. In a control group of comparable age and sex, without ACC but with generalized osteoarthritis, no calcifications were found in the tendons. On a biopsy specimen of Achilles tendon with such calcium deposits, X-ray diffraction showed that they had the characteristics of calcium pyrophosphate dilhydrate. Isolated small foci of crystals were observed on some segments of tendon bundles. The presence of fine linear calcifications on X-rays of the Achilles or quadriceps tendons may be a useful aid in the radiologic diagnosis of so-called articular chondrocalcinosis.