Lower-extremity asymmetry and patellofemoral pain in young female dancers: A 2-year follow-up

Background: Patellofemoral pain (PFP) is a prevalent injury in young dancers, with low recovery rates. This study aimed to assess PFP in young female dancers over a 2-year period while examining associations between lower-limb asymmetry and PFP. Methods: Thirty-two female dancers (aged 13.6 ± 2.9 years) were clinically examined for PFP at the baseline, 12 months later (first follow-up), and 24 months later (second follow-up). Dancers were also assessed for anthropometric measurements, joint range of movement (ROM), and muscle strength. Results: PFP was identified in 46.9%, 53.1%, and 46.9% of the dancers at the three time points, respectively. When comparing the baseline to the second follow-up, 21.9% of the dancers had recovered, 21.9% had developed PFP, and 25.0% had remained with PFP. Only 31.3% had remained healthy throughout this period. Examining muscle-strength-asymmetry in the four groups of dancers, significant interactions (time × group) were found for ankle plantar-flexor, knee extensor, hip abductor, and hip extensor muscle strength (p <.001), indicating that dancers in the developed-PFP or remained-PFP groups had greater muscle-strength-asymmetry at baseline than the recovered or healthy groups. Significant differences in the prevalence of asymmetry between the four groups were found for joint ROM (ankle en-pointe, hip abduction, hip external rotation, and hip internal rotation) (p <.05); and significant differences in the prevalence of asymmetry between the three time points were found for joint ROM (ankle en-pointe, ankle dorsiflexion, hip extension, hip abduction, and hip external rotation) (p =.05). Discussion: A high prevalence of dancers had PFP, with a limited prevalence of recovery. Dancers who developed PFP or remained with PFP had greater muscle strength and joint ROM asymmetry than their healthy or recovered counterparts. Conclusion: Screening for and addressing asymmetries in strength measures may modify the risk for PFP in dancers.