Decrease in medial meniscal extrusion after physical therapy to improve knee pain and range of motion in patients with knee osteoarthritis: A retrospective study

BACKGROUND: Medial meniscal extrusion (MME) is the medial displacement of the meniscus, which extends beyond the tibial margin. Studies have shown an association between MME and knee pain and that surgical treatment can reduce the extent of MME. Here, we describe the beneficial effects of physical therapy as a feasible conservative treatment for MME. METHODS: Data of 30 patients with knee osteoarthritis who underwent stretching of the semimembranosus tendon and passive range of motion (ROM) exercises twice a week for 8 weeks were retrospectively analyzed. MME was the measured distance between the medial meniscus and the line connecting the medial borders of the femur and tibia using ultrasound. Ultrasound findings of surrounding tissues, including the deep posterior bundle of the medial collateral ligament (dMCL), were recorded. Additionally, knee extension ROM was measured, and inner knee pain when walking was evaluated using a numerical rating scale. RESULTS: There were significant improvements between the baseline and 8 weeks for MME in the non-weight-bearing position (3.6 ± 0.3 mm vs. 3.0 ± 0.4 mm), MME in the weight-bearing position (4.3 ± 0.4 mm vs. 3.8 ± 0.5 mm), ROM (−12.3° ± 4.1° vs. −3.1° ± 3.8°), and knee pain (7.0 ± 0.9 vs. 1.1 ± 1.4) (each p < 0.001). In almost all cases in which the knee extension ROM improved, the dMCL was bulging at the baseline; after 8 weeks, the dMCL was flattened, suggesting ligament tension on ultrasound imaging. CONCLUSION: Stretching of the semimembranosus tendon and passive ROM exercises may reduce the extent of MME in patients with knee osteoarthritis. The ultrasound findings suggest that improvement in knee extension ROM may have led to the re-acquisition of MCL tension, which may have influenced MME reduction. Therefore, physical therapy may be a feasible conservative treatment for the reduction of MME.