Knee laxity after complete anterior cruciate ligament tear: a prospective study over 15 years

There is limited knowledge of knee laxity in the long term after a complete anterior cruciate ligament (ACL) tear treated without ACL reconstruction. The aim of this study was (1) to describe the clinical course of knee laxity after a complete ACL tear over 15 years, and (2) to study the association between knee laxity and meniscal injuries and the development of knee osteoarthritis (OA). We studied 100 consecutive subjects [mean (SD) age 26 (8) years] presenting with acute ACL injury prospectively. The initial treatment in all subjects was knee rehabilitation without reconstructive surgery. The subjects were examined with Lachman's and pivot‐shift tests at baseline, 6 weeks, 3 months, 1 year, 3 years and 15 years after the injury. Sagittal knee laxity was also evaluated with the KT‐1000 arthrometer at the 15‐year follow‐up. During follow‐up, 22 subjects were ACL reconstructed due to unacceptable knee instability. There was only a mild remaining knee laxity [median Lachman grade and pivot‐shift test value of 1 on a 4‐grade scale (0–3)] after 15 years in subjects treated without primary ACL reconstruction. Knees with higher anterior sagittal knee laxity 3 months after the injury had a worse long‐term outcome with respect to meniscal injuries and knee OA development.