The purpose of this study was to compare four common rehabilitation exercises used in physical therapy clinics for activating the vastus medialis oblique (VMO) and vastus lateralis (VL). Thirty-four subjects, aged 22-28 years, without patellofemoral pain syndrome (PFPS) (18 females and 16 males) were recruited. Subjects performed four exercises—straight leg raise with neutral and externally rotated hip positions (SLRN, SLRER), and short arc quad with neutral and externally rotated hip positions (SAQN, SAQER). The integrated electromyographic (iEMG) activity of the VMO and VL and were recorded, with means of the VMO, VL and VMO/VL compared across exercises. No significant difference was found for the VMO/VL ratio across the four exercises (p=0.147). However, for the VMO and VL individually, a significant difference was found (p=0.0001), SAQER was significantly greater than SLRN and SLRER; SAQN was significantly greater than SLRN and SLRER.

These findings suggest that exercises including short arc quad knee extensions are more effective for both the VMO and VL activation than those incorporating straight leg raises, and potentially more beneficial in the rehabilitation of patients with PFPS.