Joint Effusion at 3 Months After Anterior Cruciate Ligament Reconstruction: Its Risk Factors and Association With Subsequent Muscle Strength and Graft Remodeling

Background: Joint effusion at 3 months after anterior cruciate ligament (ACL) reconstruction is a risk factor for ACL reinjury. However, factors associated with joint effusion at 3 months postoperatively and the effect of joint effusion on subsequent quadriceps muscle strength and graft remodeling remain unknown.

Purposes: To identify factors associated with joint effusion and investigate the association between joint effusion and quadriceps muscle strength and graft remodeling in the postoperative period.

Study design: Case-control study; Level of evidence, 3.

Methods: In this retrospective multicenter study, the medical records of patients who underwent single-bundle ACL reconstruction between 2015 and 2021 were reviewed. The study included the data of 174 patients (mean age, 23.5 ± 10.6 years). Demographic data, including sex, age at surgery, time from injury to surgery in months, body mass index, preinjury Tegner activity score, presence of meniscus, and chondral injuries, were collected. Magnetic resonance imaging was performed 3 months postoperatively. Joint effusion was defined as grade 3 (range of grades, 0-3) according to the ACL Osteoarthritis Score. Isokinetic strength testing was performed at 60 deg/s, while the limb symmetry index (LSI) of quadriceps strength was evaluated at 6 months postoperatively. Moreover, graft remodeling was evaluated using magnetic resonance imaging-derived signal intensity ratio (SIR) measures at 1 year postoperatively. The authors used multivariate logistic and linear regression analyses to identify the factors influencing joint effusion at 3 months and those associated with postoperative quadriceps strength LSI and SIR values, respectively.

Results: Greater preinjury Tegner activity scores (odds ratio, 1.59; 95% CI, 1.08 to 2.34; P = .02) increased the odds of joint effusion at 3 months postoperatively. Multivariable linear regression analysis revealed that joint effusion (β = -23.8; 95% CI, -36.0 to -11.7; P < .001) was an independent factor associated with LSI of the quadriceps. Furthermore, joint effusion (β = 1.33; 95% CI, 0.53 to 2.14; P = .001) was associated with a higher SIR value of the reconstructed graft.

Conclusion: The preinjury Tegner activity score was a factor associated with joint effusion at 3 months postoperatively, and joint effusion was associated with subsequent muscle weakness and delayed graft remodeling.