Exploring the biomechanical mechanisms of neuromuscular joint facilitation intervention in patients with knee osteoarthritis: a finite element analysis.

INTRODUCTION

Knee osteoarthritis (KOA) causes joint pain and gait disorders in older adults. Exercise is an effective non-pharmaceutical therapy. Neuromuscular joint facilitation (NJF) improves knee joint function by combining neuromuscular facilitation with intra-articular joint motion; however, its biomechanical mechanism remains unclear. Finite element analysis, the mechanisms by which two NJF movement patterns-knee extension with lateral tibial rotation and knee flexion with medial tibial rotation-affect the stress distribution on the meniscus and major ligaments in patients with KOA.

METHODS

Six KOA patients were recruited. Inertial motion capture and handheld dynamometer measured tibial rotation angles and force conditions: active knee extension/flexion (AKE/AKF) pattern, distally single-resisted knee extension and flexion (DKE/DKF) pattern, and NJF technique (double-resisted movement). A knee finite-element model was built from one subject's CT/MRI. Loaded parameters were used to analyze the stress distribution characteristics of the medial collateral ligament (MCL), lateral collateral ligament (LCL), anterior/posterior cruciate ligament (ACL/PCL), and medial/lateral menisci at flexion angles of 0°, 30°, 60°, and 90°.

RESULTS

Knee rotation ICCs from inertial motion capture were all >0.75 (P < 0.05). In the knee flexion-medial tibial rotation pattern, at all flexion angles, meniscal stress was highest during AKF and lowest during NJF; conversely, ligament stress was lowest during AKF and highest during NJF. In the extension-lateral tibial rotation mode, meniscal stress was highest during AKE and lowest during NJF, whereas ligament stress changes were angle-dependent. The NJF technique can produce a traction effect along the long tibial axis by coordinating proximal and distal tibial resistances. This applies a force of approximately 30° to the long axis of the tibia, thereby reducing the load within the joint capsule.

DISCUSSION: The NJF technique can redistribute load between the meniscus and ligaments in this subject-specific finite element model, reducing peak meniscal load while moderately increasing ligament mechanical stimulation. These computational findings suggest a distinctive biomechanical profile of NJF compared with traditional resistance training in this subject-specific model. This provides a preliminary theoretical basis for future research, but the clinical relevance of these biomechanical observations requires confirmation through prospective clinical trials.