Relationship between patellar tilt and VL:VM activation ratio for (A) pain-free controls and all PF pain (PFP) subjects, and (B) PFP subjects classified into normal tracking and maltracking groups. The regression line represents a significant relationship (R2 = 0.72, p = 0.002) in maltracking PFP subjects. No significant relationships existed between tilt and VL:VM activation ratio in pain-free controls (R2 = 0.01, p = 0.70), all PFP subjects (R2 < 0.01, p = 0.949), or normal tracking PFP subjects (R2 = 0.01, p = 0.652).