INCIDENCE OF SUBSEQUENT ADJACENT JOINT INJURY AFTER A PATELLOFEMORAL PAIN DIAGNOSIS AND THE PROTECTIVE ROLE OF EXERCISE THERAPY

D.I. Rhon^1,2, T.C. Sell³, K.S. Foster¹, T.A. Greenlee¹, J.L. Young⁴

¹Brooke Army Medical Center, Department of Rehabilitation Medicine, San Antonio, United States, ²Uniformed Services University of the Health Sciences, Department of Rehabilitation Medicine, Bethesda, United States, ³Atrium Health Musculoskeletal Institute, Charlotte, United States, ⁴Bellin College, Science in Physical Therapy Program, Green Bay, United States

Background: Patellofemoral pain is one of the most common knee disorders in younger adults; associated with repetitive activities that lead to reduced physical activity. Because of the knee’s role in the lower extremity kinematic chain, the factors contributing to patellofemoral pain may also affect adjacent joints proximal or distal to the knee.

Purpose: To investigate the incidence of subsequent lumbar, hip, and ankle injuries after an initial patellofemoral injury. A secondary purpose was to identify the relationship between the use and timing of therapeutic exercise for patellofemoral pain and the incidence of adjacent joint injuries.

Methods: Indivdiuals seeking care for patellofemoral pin in a large government health system in the U.S. between 2010-2011 were included. Only individuals with a complete 2-year follow-up period were included, and anyone with a prior knee injury of any kind in the past year was excluded. Episodes of care that included therapeutic exercise were identified. Frequency of adjacent joint injuries in the 2-year period after initial patellofemoral pain injury, hazard ratios (HR) with 95% confidence intervals, and Kaplan-Meier survival curves for risk of adjacent joint injury based on receiving therapeutic exercise for the initial injury were calculated.

Results: After the initial patellofemoral pain diagnosis, 42,983 (46.6%) individuals sought care for an adjacent joint injury. Of these, 19,587 (21.2%) were had a lumbar injury, 2,837 (3.1%) a hip injury, and 10,166 (11.0%) an ankle injury. One in five (19.5%; n=17,966) received therapeutic exercise which reduced the risk of having a subsequent lumbar (HR=0.78, 95% CI 0.76-0.81), hip (HR=0.93, 95% CI 0.87-0.98) or ankle-foot (HR=0.86, 95% CI 0.83-0.90) injury.

Conclusions: The results suggest that a high number of individuals with patellofemoral pain will sustain an adjacent joint injury within two years although causal relationships cannot be determined. Receiving therapeutic exercise for the initial knee injury reduced the risk of sustaining an adjacent joint injury. This study helps provide normative data for subsequent injury rates in this population and guide the development of future studies designed to understand causal factors.

Implications: Clinicians should consider that almost 50% of individuals they are treating for patellofemoral pain may go on to develop adjacent joint pain (ankle, hip, lumbar spine), but utilizing exercise therapy to treat patellofemoral pain may reduce the risk of future injury.

Keywords:
patellofemoral pain
musculoskeletal injury
exercise therapy

Topics:
Musculoskeletal: lower limb
Sport & sports injuries

Did this work require ethics approval? Yes

Institution: Brooke Army Medical Center

Committee: Army Regional Health Command Central IRB

Ethics number: C.2016.048n