Abstract
CONTEXT: Knee injuries are prevalent, and the associated knee pain is linked to disability. The influence of knee pain on movement biomechanics, independent of other factors related to knee injuries, is difficult to study and unclear. OBJECTIVE: (1) To evaluate a novel experimental knee-pain model and (2) better understand the independent effects of knee pain on walking and running biomechanics. DESIGN: Crossover study. SETTING: Biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: Twelve able-bodied volunteers (age = 23 ± 3 years, height = 1.73 ± 0.09 m, mass = 75 ± 14 kg). INTERVENTION(S): Participants walked and ran at 3 time intervals (preinfusion, infusion, and postinfusion) for 3 experimental conditions (control, sham, and pain). During the infusion time interval for the pain and sham conditions, hypertonic or isotonic saline, respectively, was continuously infused into the right infrapatellar fat pad for 22 minutes. MAIN OUTCOME MEASURE(S): We used repeated-measures analyses of variance to evaluate the effects of time and condition on (1) perceived knee pain and (2) key biomechanical characteristics (ground reaction forces, and joint kinematics and kinetics) of walking and running (P < .05). RESULTS: The hypertonic saline infusion (1) increased perceived knee pain throughout the infusion and (2) reduced discrete characteristics of each component of the walking ground reaction force, walking peak plantar-flexion angle (range = 62°-67°), walking peak plantar-flexion moment (range = 95-104 N·m), walking peak knee-extension moment (range = 36-49 N·m), walking peak hip-abduction moment (range = 62-73 N·m), walking peak support moment (range = 178-207 N·m), running peak plantar-flexion angle (range = 38°-77°), and running peak hip-adduction angle (range = 5-21°). CONCLUSIONS: This novel experimental knee pain model consistently increased perceived pain during various human movements and produced altered running and walking biomechanics that may cause abnormal knee joint-loading patterns.