Reduced lower extremity strength, altered muscle activation, and unchanged kinetics during single-leg squatting in males with patellofemoral pain versus pain-free males: A cross-sectional analysis

BACKGROUND: Patellofemoral pain is frequently a cause of reduced quality of life in physically active males. The cause of patellofemoral pain is theorized to include aberrant biomechanics during weight-bearing activities. Altered biomechanics of females with patellofemoral pain have been reported, but there is a dearth of research for males with this condition. This study aimed to compare males with and without patellofemoral pain for hip and knee joint moments and muscle activation during single-leg-squatting and proximal muscle strength. METHODS: Twenty males with patellofemoral pain and 20 pain-free males aged 20-39 years performed single-leg-squatting while motion, ground reaction force, and proximal muscle electromyographic activity were captured. Isometric muscle strength of the hip extensors, hip abductors, knee extensors, and knee flexors were measured with a dynamometer. Triplanar joint moments of the weight-bearing hip and knee, proximal muscle activation, and isometric strength of the groups were compared using mixed model ANOVAs. FINDINGS: Males with patellofemoral pain had greater gluteus maximus activation during single-leg-squatting than pain-free controls (p = 0.045) but no difference for hip and knee joint moments (p > 0.05). Patellofemoral pain participants had lower hip and knee muscle strength than controls with significantly reduced strength for hip abductors (peak torque/body mass group means: patient = 1.23; control = 1.48; p = 0.012) and knee flexors (peak torque/body mass group means: patient = 1.06; control = 1.39; p = 0.004). INTERPRETATION: Males with patellofemoral pain may have proximal muscle weakness which may cause compensatory increased hip and knee muscle activation to perform weight-bearing activities. Clinicians should consider knee flexor strengthening in management of males with patellofemoral pain.