Degeneration in ACL Injured Knees with and without Reconstruction in Relation to Muscle Size and Fat Content-Data from the Osteoarthritis Initiative

Abstract

Background: Anterior cruciate ligaments (ACL) injuries represent a major risk factor for early osteoarthritis (OA).

Purpose: To evaluate the prevalence and 4-year progression of knee OA measured with 3T MR-imaging in individuals with ruptured, reconstructed or normal ACL and to assess the impact of thigh muscle characteristics.

Methods: A total of 54 knees (23/54 male, 31/54 female) were recruited from the Osteoarthritis Initiative (OAI). At baseline, 15/54 subjects had prevalent ACL ruptures and 15/54 subjects had prevalent ACL reconstruction (24/54 normal ACL). Western Ontario and McMasters Universities Arthritis Index (WOMAC) scores, Physical Activity Scores of the Elderly (PASE) and thigh muscle characteristics including strength, fat infiltration (Goutallier score) and thigh muscle cross-sectional area (CSA) MR measurements were obtained at baseline. Whole-organ MR-imaging Scores (WORMS) were obtained at baseline and at a 4-year follow-up time-point. Multivariate regression models, adjusting for covariates (age, gender, body mass index), were used for statistical analysis.

Results: At baseline, subjects with prevalent ACL ruptures had worse WORMS total scores (mean±SEM, 44.1±3.5) than subjects with ACL reconstruction (30.8±4.0; P = 0.015) and worse than subjects with normal ACL (21.3±3.0; P<0.001). Cartilage scores were worse in both femorotibial compartments in ACL injured knees than in knees with normal ACL (P<0.05). Knees with ACL reconstruction showed an increased degeneration of the medial meniscus (P = 0.036), cartilage degeneration at the medial femoral condyle (P = 0.011). In a multivariate regression model, including both ACL groups and total muscle characteristics as influence parameters, high thigh muscle CSA, high muscle/ fat ratio and low Goutallier scores were associated with less degenerative changes at the knee, independent of ACL status. Knees with ACL reconstruction showed an increased progression of cartilage degeneration at the medial tibia compared to the normal ACL group (P = 0.027).

Conclusions: High thigh muscle CSA is associated with less degenerative changes at the knee, independent of the ACL status and may potentially be advantageous in the prevention of early OA.

Fig 1. Segmentation on axial T1-w images of the thigh.

Segmentation was performed for the vastus medius (VM), intermedius (IM) and lateralis (VL), rectus femoris (RF), sartorius (S), gracilis (G), adductor magnus (AM), adductor longus (AL), short head of biceps (SBF), long head of biceps (LBF), semitendinosus (ST), semimembranosus (SM), total thigh circumference (TC) and femur circumference (FC). Examples are given of four different individuals. (A) high muscle volume, high muscle/ fat ratio. (B) high muscle volume, small muscle/ fat ratio. (C) small muscle volume. (D) high fatty infiltration of thigh muscles.

Fig 2. Muscle characteristics.

Mean±SEM are given for the different ACL groups, controlling for the co-variates age, gender and BMI. ACL, anterior cruciate ligament; CSA, cross-sectional area; VL, vastus lateralis muscle; VM, vastus medialis muscle. *P<0.05.