Acute hemarthrosis of the knee in children.

The purpose of this study was to determine the cause of acute hemarthrosis of the knee in a prospective pediatric patient population. Between December 1988 and August 1991, 21 consecutive children who were seen with an acute traumatic hemarthrosis of the knee had an arthroscopic evaluation. The average age of the children at the time of injury was 14 years, 3 months (range, 10 to 17 years). The mechanism of injury was a torsional strain to the knee in 12 (71%) of the 17 patients who could accurately remember the injury. The initial evaluation included a history, physical examination, and anteroposterior, lateral, sunrise, and comparison radiographs. The arthroscopic procedure was performed under general anesthesia, and the arthroscopic findings were compared with preoperative findings. During arthroscopic examination, an osteochondral fracture of the lateral femoral condyle or patella was identified in 14 (67%) of the 21 patients. Preoperative radiographs failed to identify the fracture in 5 (36%) of the 14 patients who had an osteochondral fracture. The anterior cruciate ligament was visualized and probed; an injury was found in only two cases (10%). We concluded that in children an acute traumatic hemarthrosis reflects a major injury to the knee. The children in this study had a high frequency of osteochondral fractures; ACL injuries were found in only two patients. Because of the unreliable nature of radiographic evaluation, arthroscopic evaluation is a valuable tool in differential diagnosis and treatment of acute hemarthrosis of the knee.