Dose-Response Relationship of Ambulatory Load and Cartilage Pilot Study

Background: Ambulatory load plays an important role in the initiation and progression of osteoarthritis. It is unknown if load-induced changes in articular cartilage biomarkers depend on the magnitude of ambulatory load.
Methods: Serum cartilage oligomeric matrix protein sCOMP was assessed before and after a 30-minute walking stress test performed on three test days by 24 healthy volunteers. In each walking stress test, one of three ambulatory loads was applied: normal body weight (100%BW = normal load); reduced body weight (80%BW = reduced load); increased body weight (120%BW = increased load). Knee kinematics and ground reaction force were measured using an inertial sensor gait analysis system and a pressure plate embedded in the treadmill.
Results: Load-induced increases in sCOMP rose with increasing ambulatory load magnitude. Mean sCOMP levels increased immediately after the walking stress test by 26.8 ± 12.8%, 28.0 ± 13.3% and 37.3 ± 18.3% for the reduced, normal or increased load condition, respectively. Knee kinematics did not differ between conditions.
Conclusion: The results of this study provide important evidence of a dose-response relationship between ambulatory load magnitude and load-induced changes in sCOMP. Our data suggests that in normal weight persons sCOMP levels are more sensitive to increased than to reduced load.