Impaired Corticospinal Excitability of the Quadriceps in Individuals With Patellofemoral Pain is Associated With Worse Pain, Function, and Strength

CONTEXT: Quadriceps impairment is evident in patellofemoral pain, yet its underlying mechanisms remain unclear, particularly the potential contribution of corticospinal mechanisms. We aimed to explore corticospinal excitability of the quadriceps in individuals with patellofemoral pain.

DESIGN: Cross-sectional.

METHODS: We included 21 individuals with patellofemoral pain (57% women) and 21 pain-free controls (66% women). Corticospinal excitability was assessed via transcranial magnetic stimulation, measuring resting motor threshold, active motor threshold, cortical silent period, and short-interval intracortical inhibition. Quadriceps strength (Lafayette Manual Muscle Tester) and force sense (Chattanooga Stabilizer Pressure Biofeedback) were evaluated bilaterally in the patellofemoral pain group and in the dominant limb of pain-free controls. Self-reported measures included pain intensity, knee function, physical activity, and kinesiophobia.

RESULTS: Individuals with patellofemoral pain had a longer cortical silent period duration than pain-free controls (ηp2=.133, p = .030). A longer cortical silent period was associated with greater pain duration (r = .389, p = .021) and pain intensity (r = .345, p = .042) and lower knee function (r = -.366, p = .030) and quadriceps strength (r = -.298, p = .029). No between-group or between-limb differences were found for resting motor threshold, active motor threshold, or short-interval intracortical inhibition.

CONCLUSIONS: Individuals with patellofemoral pain exhibited bilaterally longer cortical silent periods, reflecting increased cortical and corticospinal inhibition. Associations with pain, function, and strength suggest that neurophysiological alterations may contribute to clinical manifestations. These findings provide novel insights that could inform future rehabilitation strategies for patellofemoral pain.