The Effects of Quadriceps Strengthening Exercise on Quadriceps Muscle Biomechanics During Locomotion in Adults with Knee Osteoarthritis

Abstract

Knee Osteoarthritis (OA) is a disease characterized by knee joint deterioration and pain, while also being associated with altered knee joint mechanics and quadriceps strength deficits. Research investigating the effects of quadriceps-strengthening exercise on knee OA has shown improvements in symptoms, function, and strength, but minimal changes to joint mechanics. It is speculated that improved quadriceps muscle biomechanics are the mechanism responsible for this improvement in symptoms, though this concept is untested. The purpose of this study is to examine the effects of quadriceps strengthening exercise on quadriceps muscle biomechanics during level walking, stair ascent, and stair descent in adults with knee osteoarthritis. Three-dimensional kinematic, ground reaction force, isokinetic strength, and WOMAC data were collected on 10 adults with uni- or bi-lateral knee OA. During the 12-week period between the testing procedures, 6 adults participated in strengthening exercise, while the other 4 adults went untrained. Quadriceps biomechanics were quantified using kinetic data collected during level walking, stair ascent, and stair descent tasks in combination with a mathematical knee model. A 2x2 repeated measures ANOVA (p<0.05) was used to analyze each symptomatic, strength, joint kinetic, and muscle biomechanics parameter. Only the training group experienced significant improvements in pain, function, and strength (All p<0.02). At follow-up, this group climbed and descended stairs at faster velocities (Both p<0.03), exhibited greater knee extensor torque and power during level walking (Both p<0.03), experienced increased quadriceps force and work during level walking and stair ascent (All p<0.05), and exhibited increased knee compressive force during all three conditions (All p<0.03). The results of this study reinforce the notion that quadriceps-strengthening exercise reduces pain and improves function in adults with knee OA. The data refute the study hypothesis by suggesting that quadriceps muscle biomechanics are, in fact, altered following a strengthening protocol. Study results also refute claims that reduced joint loads are the cause of pain relief by showing significant increases in knee compressive force alongside significant improvements in pain and physical function. Because of the limited number of participants used, more work is needed.