The Correlation Between Knee Pain Severity During Early Rehabilitation Exercise After Anterior Cruciate Ligament Reconstruction and Presence of Patellofemoral Joint Degeneration.

Background: Patellofemoral osteoarthritis is a recognized complication after anterior cruciate ligament (ACL) reconstruction (ACLR). Nevertheless, previous studies have not adequately addressed the connection between pain severity and the presence of early patellofemoral osteoarthritis during initial rehabilitation exercises after ACLR.

Purpose: To explore the correlation between knee pain severity during early flexion exercises and chondral changes of the patellofemoral joint.

Study design: Cohort study; Level of evidence, 3.

Methods: We included 121 patients who underwent ACLR. Patients were categorized into 3 groups based on their Numeric Rating Scale pain scores during rehabilitation exercises. Group A consisted of pain levels <3 points, group B had scores 4 to 6 points, and group C had scores ranging from 7 to 10 points. Magnetic resonance imaging (MRI) assessments were conducted preoperatively and 3 months postoperatively, utilizing T2-mapping MRI sequences to evaluate the composition of patellofemoral articular cartilage. We also performed subjective assessments using International Knee Documentation Committee (IKDC), Knee injury and Osteoarthritis Outcome Score (KOOS), Lysholm, and Kujala scoring systems preoperatively and postoperatively.

Results: The T2 values demonstrated statistically significant differences between groups A and C in the trochlear lateral condyle (31.5 ± 3.3 vs 34.8 ± 3.0; P < .01), trochlear groove (32.8 ± 3.4 vs 36.1 ± 4.0; P < .01), lateral surface of the patella (32.9 ± 3.2 vs 35.9 ± 3.7; P < .01), and ridge of the patella (32.6 ± 3.3 vs 36.0 ± 3.9; P < .01) at 3 months postoperatively. Significant differences were also noted between groups A and B in the trochlear lateral condyle (31.5 ± 3.3 vs 32.9 ± 3.0; P < .05), trochlear groove (32.8 ± 3.4 vs 34.7 ± 3.9; P < .05), and ridge of the patella (32.6 ± 3.3 vs 34.2 ± 4.0; P < .05). Comparisons between groups B and C further illustrated differences in the trochlear lateral condyle (P < .01) and ridge of the patella (P < .05). Subjective evaluations revealed significant differences between group A and group C in IKDC, KOOS, Lysholm, and Kujala scores 3 months after surgery.

Conclusion: This study indicates that knee pain during early rehabilitation exercises after ACL reconstruction is associated with MRI changes in the patellofemoral joint and that more intense pain perception during early rehabilitation exercises is associated with more severe changes.