Familial Absence of the Patella

Bilateral absence of the patella as an isolated congenital abnormal ity is an extreniely rare condition. The only previous report of a case we have been able to find was in a nine-year-old girl reported by Kutz in I 949. The faniily reported here is unique. Two members of the family have been found with absent patellae. Clinical examination failed to reveal any stigmata of hereditary osteo-onychodys plasia. Case Report A fourteen-year-old black boy was first seen in November I972 because of a cystic mass in the anterior aspect of the right knee, which had been present for approximately one year and was reported to have disappeared on one occasion, but to have recurred. The patient was active in sports and the knee had begun to bother him in those activities. His height was 153 centimeters and he weighed thirty-six kilograms. There was slight genu varum, and both patellae were absent (Fig. 1). Knee extension was 0 degrees bilaterally, and maximum voluntary flexion was 135 degrees. There was no lateral instability ofthe knee. There was a cystic mass lateral to the patellar tendon at the level of the knee joint, two centimeters in diameter, which was aspirated and yielded a clear, amber, gelatinous fluid. The elbows were normal as were the nails of the fingers and toes. The pelvis was palpated easily in this slender boy and there were no palpable iliac horns. The pupils were round and equal. The ankles were slender. Roentgenographic examination of the knees confirmed the absence of the patellae (Fig. 2). Roentgenograms of the elbows were normal. Roentgenograms of the pelvis were negative for the presence ofiliac horns. The cyst refilled after each of two aspiration procedures and since the cyst was enlarging and interfering with the patient's activity, surgical excision was done. The hospital work-up Flexed knees. Note the prominence offemoral condyles due to absence of patellae