Hemarthrosis of the clinically stable knee due to sports and military training in young recruits: an arthroscopic analysis.

Findings of an early arthroscopy performed in 108 consecutive hemarthrotic and clinically stable knees were analyzed. The patients were young conscripts, the mean age being 19.9 years. Fifty-seven of the knees were injured during military training, 36 in different sports activities, 9 at falls, and 6 in motorbike accidents. The lesions were divided into "primary" (lesions needing operative treatment or the supposed most common lesions in incidence) and "secondary" (other lesions). An average of 1.6 lesions were observed per knee. Dislocation of the patella was the most common diagnosis in 38 (35%) cases. Dislocation of the patella was associated with military exercise (p < 0.001). Lesions of the anterior cruciate ligament (ACL) were observed in 37 (34%) cases. ACL ruptures were related to sport activities (p < 0.0001).