Date of Paper/Work


Type of Paper/Work

Research Project

Degree Name

Doctor of Physical Therapy (DPT)


Physical Therapy

First Advisor

John S. Schmitt


BACKGROUND AND PURPOSE: Patellofemoral pain syndrome (PFPS) is one of the most prevalent orthopedic conditions affecting young athletes today. Epidemiological studies have reported PFPS to be the most common injury seen in runners. Deficits in hip strength have been identified in runners with PFPS, but core endurance in relation to knee pain has not been well documented. The primary purpose of our study was to investigate differences in hip strength and core endurance between female, adolescent runners with PFPS and their age matched controls. The secondary purpose of our research was to examine any correlations between hip strength and core endurance in our participants.

METHODS: A cross sectional design was used. We recorded pain, Kujala score, hip strength and endurance and core endurance in 34 adolescent female cross country runners. Cases with PFPS were defined as young female runners with a minimum three month history of anterior knee pain of insidious onset and had a most severe knee pain rated 3/10 or higher. Control subjects had no history of knee surgery, traumatic knee injuries, patellar instability, or neurologic conditions. Between-group differences and correlations were calculated between age-matched cases and controls using t-tests. Pearson correlation coefficients were used to determine associations for selected measures.

RESULTS: No significant differences were observed between cases and controls for hip strength and endurance. However, there was a large percent difference between cases and controls in selected core endurance measures. It was found that all hip strength and core endurance results had low correlations ( < 0.28). Among cases with PFPS, a strong and significant, negative correlation was found between subjects’ reported worst pain and Kujala score (r=-0.79, p<0.05)). A non-significant moderate negative correlation between side plank endurance and usual pain was found (r=-0.49).

CONCLUSION: There were minimal differences noted in isometric strength tests between groups. There was a clear difference noted with endurance testing between groups. However, this difference was not found to be significant, which could be due to low number of subjects with PFPS. The differences in endurance between athletes with PFPS and their pain free counterparts merit further investigation and research. Of note, it was found that strength and endurance had a minimal correlation; this indicates that clinically, endurance cannot be inferred from isometric strength testing. Therefore, we recommend clinicians perform specific measures of endurance when attempting to identify impairments in runners with PFPS.