The Relationship Between Periarticular Muscle Properties and Knee Pain in Non-Overweight Postmenopausal Females

Objective

To determine how properties of periarticular muscle relate to knee OA outcomes, specifically how inter- and intramuscular fat (IMF) content (percentage, volume) and muscle volume relate to knee pain and function among non-overweight postmenopausal females (non-OW PMF).

Methods

In this cross-sectional study, 51 non-OW PMF (BMI<25 kg/m², 50–85 years) with evidence of early knee OA underwent 3T knee magnetic resonance (MR) imaging (T1-weighted, 2-point Dixon, in-phase images, voxel size: 0.7 × 0.7 × 2.0 mm). Muscle features from MR images of the knee were segmented to compute muscle properties (percentage and volume of IMF, muscle volume). Multivariable linear regression determined the relationships between these muscle properties (slice-wise and volume-wise) and of knee pain (Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire, Intermittent and Constant Osteoarthritis Pain) and function (40 m walk, 30 s chair stand, 9-step stair climb).

Results

Due to missing parameters, only 42 participants were included in the final analysis (mean age = 62±9 years, BMI = 22.7 ± 3.2 kg/m², KL score ≥ 2: 14(34.2 %)). A 10 % higher IMF percentage across the full volume of calf slices, but not thigh, was associated with pain scores reflecting greater KOOS knee pain (b = -25.27(-38.44, -12.10)), intermittent pain (b = 36.81(19.25, -54.38)), and constant pain (b = 21.32(2.00, 40.64), as well as longer 40 m walk times (b = 8.43(0.64, 16.21)). b refers to the unstandardized beta coefficient.

Conclusion

Greater IMF in the periarticular calf is associated with greater knee pain and worse functional status among non-OW PMW with varying degrees of knee pain. Our finding highlights the need to closely study the role of the periarticular calf in knee OA by extending knee MRI scans to encompass a larger field of view to capture more muscle both proximal and distal from the joint line.