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Background: Anterior cruciate ligament (ACL) reconstruction can effectively return athletes to the playing field, but they are still at risk of developing posttraumatic osteoarthritis (PTOA). No studies have used multivariable analysis to evaluate the predictors of radiographic PTOA in the lateral compartment of the knee at short-term follow-up after ACL reconstruction., Purpose: To determine the predictors of radiographic joint space narrowing in the lateral compartment 2 to 3 years after ACL reconstruction in a young, active cohort., Study Design: Cohort study; Level of evidence, 2., Methods: A nested cohort of 358 patients from the Multicenter Orthopaedic Outcomes Network (MOON) prospective cohort who were aged ≤33 years, were injured playing a sport, and had never undergone surgery on the contralateral knee were followed up 2 years after ACL reconstruction with questionnaires and with weightbearing knee radiographs using the metatarsophalangeal (MTP) joint technique. The joint space width in the lateral compartment was measured using a semiautomatic computerized method, and multivariable predictive modeling was used to evaluate the relationship between meniscus treatment, cartilage injury, graft type, and joint space while adjusting for age, sex, body mass index, and Marx activity score., Results: The mean lateral joint space width was 0.11 mm narrower on the ACL-reconstructed knee compared with the contralateral healthy knee (7.69 mm vs 7.80 mm, respectively; P < .01). Statistically significant predictors of a narrower joint space width on the ACL-reconstructed knee included lateral meniscectomy ( P < .001) and a Marx activity score less than 16 points ( P < .001)., Conclusion: This study identifies lateral meniscectomy and a lower baseline Marx activity score to be predictors of radiographic joint space narrowing in the lateral compartment 2 to 3 years after ACL reconstruction in young, active patients without a prior knee injury.

Objective: To identify risk factors for radiographic signs of post-traumatic osteoarthritis (OA) 2-3 years after anterior cruciate ligament (ACL) reconstruction through multivariable analysis of minimum joint space width (mJSW) differences in a specially designed nested cohort., Methods: A nested cohort within the Multicenter Orthopaedic Outcomes Network (MOON) cohort included 262 patients (148 females, average age 20) injured in sport who underwent ACL reconstruction in a previously uninjured knee, were 35 or younger, and did not have ACL revision or contralateral knee surgery. mJSW on semi-flexed radiographs was measured in the medial compartment using a validated computerized method. A multivariable generalized linear model was constructed to assess mJSW difference between the ACL reconstructed and contralateral control knees while adjusting for potential confounding factors., Results: Unexpectedly, we found the mean mJSW was 0.35 mm wider in ACL reconstructed than in control knees (5.06 mm (95% CI 4.96-5.15 mm) vs 4.71 mm (95% CI 4.62-4.80 mm), P < 0.001). However, ACL reconstructed knees with meniscectomy had narrower mJSW compared to contralateral normal knees by 0.64 mm (95% C.I. 0.38-0.90 mm) (P < 0.001). Age (P < 0.001) and meniscus repair (P = 0.001) were also significantly associated with mJSW difference., Conclusion: Semi-flexed radiographs can detect differences in mJSW between ACL reconstructed and contralateral normal knees 2-3 years following ACL reconstruction, and the unexpected wider mJSW in ACL reconstructed knees may represent the earliest manifestation of post-traumatic osteoarthritis and warrants further study., (Copyright © 2015. Published by Elsevier Ltd.)