We reviewed three cases of histologically confirmed benign chondroblastoma around the knee joint and discussed problems in diagnosis and prognosis.
Case 1: 17-year-old boy, complaining of right knee pain. X-ray pictures showed a translucent area with perifocal sclerosis in the medial condyle of the distal femur. 2 years after curettage and bone graft, there is on problem clinically and radiologically.
Case 2: 19-yer-old boy. At the time of his first episode of knee pain during sport activities, radiograms showed on evidence of any abnormality. Two years later knee pain and motion disturbances increased. On X-ray examination, there was a 5×6cm radiolucent area in the distal femoral epiphysis invading the articular surface. Seven years after curettage and bone graft, he had knee pain and osteoarthritic changes radiologically.
Case 3: 13-year-old girl, complaining of knee pain and motion disturbances with meniscal signs. Plain X-ray film showed no abnormalities, however, MRI demonstrated an abnormal mass in the proximal tibial epiphysis in T1-weighted view, reaching to the articular surface and growth plate. Six months after curettage and bone graft, the knee pain and motion disturbances had disappeared.
Examination of these cases of chondroblastoma around the knee joint, suggested three inportant aspects. (1) Tumor mass spreading to the articular surface may cause clinical findings of a meniscal lesion such as locking and McMurray sign. (2) X-ray pictures at an early stage may not identify the existance of femoral problems, and MRI is the most useful method for early diagnosis. (3) Tumor invasion on to the articular cartilage and growth plate may lead to osteoarthritis and growth disturbances.
