The purpose of this study is to clarify optimal timing of anterior cruciate ligament (ACL) reconstruction from the point of view of meniscus injury.

One hundred thirty-five ACL injuries (under 40 years of age) were analyzed in this study. All knees had undergone primary reconstruction without other ligament injury, and follow-up arthroscopy. ACL reconstruction was performed by the semitendinosus and gracilis method. The rehabilitation protocol was based on that of Shelbourne. Cases were divided into 4 groups by the period from injury to reconstruction. Nineteen knees were of the acute phase, which is within 1 month from the injury to reconstruction. Thirty-one knees were of the subacute phase, which is from 1 month over to reconstruction. Thirty-one knees were of the subacute phase, which is from 1 month over to 3 months from the injury to reconstruction. Forty knees were of the subchronic phase, which is from 3 months over to 1 year from the injury to reconstruction. Forty-five knees were of the chronic phase, which is over 1 year from the injury to reconstruction. We compared arthroscopic findings as well as clinical follow-up results of each phase.

The rate of lateral meniscus injury were 84% in the acute phase, 39% in the subacute phase, 58% in the subchronic phase, and 51% in the chronic phase. The rates of medial meniscus injury were 32% in the acute phase, 29% in the subacute phase, 53% in the sub-chronic phase, and 60% in the chronic phase. Horizontal tear and degenerative tear of the lateral meniscus were increased with time. Osteoarthritic change at follow-up arthroscopy was observed 3 knees in the acute phase, 4 knees In the subacute phase, 8 knees In the subchronic phase, and 13 knees in the chronic phase. There was no difference between clinical results of our ACL reconstruction in the acute phase and chronic phase.

ACL reconstruction in the acute phase was the effective method for preventing secondary osteoarthritis after medial meniscus injury.