Relationship between quadriceps strength and patellofemoral joint chondral lesions after anterior cruciate ligament reconstruction.
The incidence of the patellofemoral joint chondral lesions after anterior cruciate ligament reconstruction (ACLR) is disturbingly high. Few studies have assessed the factors affecting patellofemoral joint chondral lesions postoperatively. The recovery of quadriceps strength after ACLR could be associated with patellofemoral joint cartilage damage. Cohort study; Level of evidence, 3. A total of 88 patients who underwent arthroscopic anatomic double-bundle ACLR with hamstring autografts received second-look arthroscopy at the time of metal staple removal at an average of 24.1 months (range, 12-51 months) postoperatively. All patients underwent standardized isokinetic strength testing for bilateral quadriceps and hamstrings 1 to 2 days before second-look arthroscopy. The patients were divided into 2 groups: Patients in group 1 had a ≥20% deficit on the peak torque measures for quadriceps compared with that of the contralateral knee, whereas those in group 2 had a <20% deficit on peak torque. Cartilage status at the patellofemoral joint and tibiofemoral joint were evaluated by second-look arthroscopy and the Outerbridge classification. Other assessments included the International Knee Documentation Committee (IKDC) score, Tegner and Lysholm scores, side-to-side difference on KT-2000 arthrometer, and range of motion. There were 42 patients included in group 1 and 46 patients in group 2. The mean postoperative quadriceps peak torque of the involved knee compared with the contralateral knee was 70% (range, 57%-80%) in group 1 and 95% (range, 81%-116%) in group 2. For all patients, a significant worsening was seen in the patellar and trochlear cartilage (P = .030 and <.001, respectively) but not at the medial or lateral tibiofemoral joint after ACLR. A significant worsening in the status of both patellar and trochlear cartilage was seen after ACLR in group 1 (P = .013 and =.011, respectively) and of trochlear cartilage in group 2 (P = .006). Significantly fewer severe chondral lesions of the patella were found in group 2 than in group 1 (proportion of patients whose cartilage grade worsened: 26% vs 48%, P < .05; difference in cartilage grade: 0.09 vs 0.62, P < .05). There was no significant difference for trochlear chondral worsening between the 2 groups. No significant differences were detected between the 2 groups in terms of hamstring strength; Lysholm, Tegner, and IKDC scores; KT-2000 arthrometer anterior laxity; or range of motion. Greater than 80% recovery of quadriceps strength after ACLR is associated with less severe patellar cartilage damage at short-term follow-up.