Abstract: Objective To study the correlation between injury of anterior cruciate ligament (ACL) and benign hypermobility of joints. Methods One hundred and two patients with ACL injury admitted to our department from January 2010 to December 2011 and 154 healthy subjects were comparatively studied. Benign hypermobility of joints was diagnosed according to Beighton scale. Twelve months after arthroscopy-assisted ACL reconstruction with hamstring tendon autograft, the joint stability was assessed respectively by Lanchman's test and anterior drawer test. Results Beighton scale was no less than 4 in 39 (38.2%) of the 102 patients with ACL injury and in 32 (20.8%) of the 154 healthy subjects (P＜ 0.05). The joint stability tests with benign hypermobility of joints were negative in 26 patients and positive in 13 patients after operation whereas they were negative in 57 patients and positive in 6 patients without benign hypermobility of joints after operation (P＜ 0.05). Conclusion ACL injury is correlated with benign hypermobility of joints. The outcome of arthroscopy-assisted ACL reconstruction is poorer in patients with benign hypermobility of joints.