The influence of experimental anterior knee pain during running on electromyography and articular cartilage metabolism

Summary Objective To determine whether anterior knee pain (AKP), during running, acutely affects lower-extremity electromyography (EMG) and articular cartilage metabolism. Methods A within-subjects design was used. Each of 12 able-bodied subjects ran on a treadmill for 30 min for three different sessions: control (no infusion), sham (0.9% NaCl infusion into the involved-leg infrapatellar fat pad), and pain (5.0% NaCl infusion into the involved-leg infrapatellar fat pad). Bilateral surface EMG was monitored for the vastus medialis (VM), vastus lateralis (VL), and gastrocnemius (GA). Serum cartilage oligomeric matrix protein (COMP) concentration was determined before, after, and 60 min after the run. A functional analysis approach was used to compare EMG amplitude, across the entire stance phase, between sessions and legs. Mixed-model analysis of covariance was used to compare serum COMP concentration between sessions, across time. Results Relative to the uninvolved leg, greater involved-leg VL and GA EMG amplitude existed during midstance for the sham and control sessions ( P