32 patients with anterior cruciate ligament (ACL) injuries were randomized to receive arthroscopic ACL reconstruction and intra-articular viscoseal instillation or arthoscopic ACL reconstruction alone. Over 2 days, the viscoseal group demonstrated significantly greater knee injury osteoarthritis outcome scores (for all subscales except quality of life) than the control group. However, this difference was no longer significant at 2, 6, and 12 weeks. At days 1 and 2, there was also significantly less swelling in the viscoseal group than in the control group.