Calcium pyrophosphate dihydrate crystal deposition disease: Frequency of tendon calcification about the knee

Objective. To delineate the prevalence of tendon and cartilage calcification as well as its possible predilection for age, sex, or side of involvement in calcium pyrophosphate dihydrate (CPPD) crystal deposition disease of the knee. Methods. We reviewed 225 lateral knee radiographs from 138 patients (M/F: 85/52, 1 unspecified sex, mean age: 73 yrs) to document quadriceps and gastrocnemius tendon calcification. Chondrocalcinosis of the knee was evaluated on 275 knee radiographs (lateral and anteroposterior projection) from 153 patients (MF: 97/55, 1 unspecified sex, mean age: 73 yrs) to determine the frequency of meniscal and hyaline cartilage calcification. Results. Gastrocnemius tendon calcification was found in 28.4% of knees, which is significantly more common than quadriceps tendon calcification (8.4%). No significant age or laterality difference existed for calcification of either tendon. Quadriceps tendon calcification was more prevalent in men, but no sex difference was present for the gastrocnemius tendon. Calcification of either tendon never occurred without associated chondrocalcinosis. Meniscal calcification was significantly more prevalent than hyaline cartilage calcification; meniscal calcification also was significantly more frequent in men. Increased prevalence of calcification with age was observed in hyaline cartilage but not in the menisci. Conclusion. Gastrocnemius tendon calcification is not infrequent in CPPD crystal deposition disease of the knee; identification of such calcification may further delineate the extent of this disorder.