Hip and knee muscle function following aerobic exercise in individuals with patellofemoral pain syndrome

Patellofemoral pain syndrome (PFPS) is a commonly experienced knee disorder that can result in altered muscle activation of the surrounding musculature. There is little evidence on effects of aerobic exercise on quadriceps torque and EMG activation of the vastus medialis obliquus (VMO), vastus lateralis (VL), and gluteus medius (GM). In this study 20 healthy individuals and 20 patients with PFPS had measures of torque and muscle activation taken following aerobic exercise. A modified Balke–Ware protocol was used for the exercise intervention. Baseline and post-aerobic measurements of knee extension torque and VMO, VL, and GM activation during a single leg anterior reaching task. These measurements were only taken on the injured limb. Following exercise, knee extension torque was lower in PFPS patients when compared to controls (p = 0.03). Patients reporting no pain after exercise experienced decreases (p = 0.021) in GM activation following exercise. There was a decrease in VMO (p = 0.010) and VL (p = 0.021) activation in PFPS patients with elevated knee pain. Recreationally active individuals with PFPS may experience different responses in the quadriceps and GM after exercise. Responses may be confounded by whether or not pain is exacerbated by exercise.