We examined radiographs of the inferior pole of the patella in seven juvenile athletes diagnosed as having Sinding-Larsen-Johansson disease (SLJD) and discussed the etiology of the syndrome. Eight knees had tenderness at the inferior pole of the patella accompanied by radiographic abnormalities. A regular or irregular calcification was found at the inferior pole of the patella in three knees; coalescence of the calcification was found in two knees; incorporation of the calcification into the patella to yield a normal radiographic configuration of the area was found in two knees; and a small calcification separated from the patella was found in one knee. All of these findings varied and did not always correspond to the radiographic stages of the disease process identified by Medlar. One case was not clearly distinguished from either osteochondritis or stress fracture, and one case had a similar symptom to tendinitis. Thus, the etiology of the syndrome seems not to be unified, and the differential diagnosis between SLJD and osteochondritis, stress fracture, or tendinitis was difficult to arrive at. We were only able to conclude that the radiographic abnormalities and consequently the etiology of the syndrome vary, and therefore there is a limitation to call the syndrome accompanied by abnormal findings of the inferior pole of the patella under the umbrella term of SLJD.