Prospective Evidence for a Hip Etiology in Patellofemoral Pain

Brian Noehren; Joseph Hamill; Irene Davis

Disclosures

Med Sci Sports Exerc. 2013;45(6):1120-1124. 

In This Article

Abstract and Introduction

Abstract

Purpose: Patellofemoral pain (PFP) is the leading cause of knee pain in runners. Proximal and distal running mechanics have been linked to the development of PFP. However, the lack of prospective studies limits establishing a causal relationship of these mechanics to PFP. The purpose of this study was to prospectively compare running mechanics in a group of female runners who went on to develop PFP compared with healthy controls. It was hypothesized that runners who go on to develop PFP would exhibit greater hip adduction, hip internal rotation, and greater rear foot eversion.

Methods: Four hundred healthy female runners underwent an instrumented gait analysis and were then tracked for any injuries that they may have developed over a 2-yr period. Fifteen cases of PFP developed, which were confirmed by a medical professional. Their initial running mechanics were compared to an equal number of runners who remained uninjured.

Results: We found that female runners who developed PFP exhibited significantly greater hip adduction (P = 0.007). No statistically significant differences were found for the hip internal rotation angle (P = 0.47) or rear foot eversion (P = 0.1).

Conclusions: The finding of greater hip adduction in female runners who develop PFP is in agreement with previous cross-sectional studies. These results suggest that runners who develop PFP use a different proximal neuromuscular control strategy than those who remain healthy. Injury prevention and treatment strategies should consider addressing these altered hip mechanics.

Introduction

Patellofemoral pain (PFP) is the most common running related injury, affecting up to 2.5 million runners in the United States alone.[6,27] It is defined as pain along the retro- or peripatellar region that is exacerbated by weight bearing activities such as running, squatting, and going up and down stairs. PFP accounts for 43% of injuries military recruits suffer from, as well as up to 25% of office visits to primary care sports medicine physicians.[7,28] PFP also disproportionately affects women over men.[4] Unfortunately, even at a 5- to 20-yr follow-up, many of these individuals continue to experience pain, which has been related to a decrease in physical activity including running.[3,17,25] Emerging evidence suggests that PFP earlier in life increases the risk of developing patellofemoral osteoarthritis later in life.[30] The long-term decrease in physical activity has significant health care consequences such as an increased risk for developing diabetes and cardiovascular disease.[2] Thus, identifying the potential underlying mechanics that result in PFP is critical to effectively treat and prevent this chronic condition.

PFP is largely believed to be a stress injury. Malalignment between the patella and the femur that reduces the contact area leads to increased patellar contact stress.[21] Evidence from a growing number of cross-sectional studies suggests that females with PFP run with greater hip internal rotation and hip adduction.[19,24,31] Both motions have been shown in experimental models to increase the amount of stress on the lateral aspect of the patella and, with repetitive exposure, may result in pain.[11,14] Rear foot eversion has also been hypothesized to be related to PFP. Excessive rear foot eversion has been associated with increased knee flexion and a greater tendency toward knee abduction or genu valgus.[16] Increased knee flexion results in greater patellofemoral compressive loads, which can increase overall contact stress. Genu valgus is associated with increased Q angle, increasing the lateral component of the quad force and increasing the tendency for lateral tracking. This results in greater loads on the lateral aspect of the patellofemoral joint.[29] While many potential mechanisms have been proposed, to date, there have been few studies that have assessed the proximal and distal contribution of altered mechanics in female runners with PFP.

In summary, both hip and foot mechanics have been associated with PFP in retrospective studies. However, these studies cannot discern between cause and effect. Prospective studies are needed to help further elucidate biomechanical causes of PFP in runners. In fact, the need for such studies has been strongly advocated by numerous authors.[1,6,13] There is growing awareness of the significant health care effects that result from chronic pain conditions such as PFP. Prospective studies of the underlying mechanics that result in PFP will assist in providing the foundation for interventions for runners with PFP. Thus, the purpose of this study was to assess the gait mechanics of female runners who go on to develop PFP compared to a healthy control group who did not develop any injuries. We hypothesized that female runners who go on to develop PFP would have greater hip adduction, hip internal rotation, and rear foot eversion when compared to a healthy runners who did not develop PFP.

Comments

3090D553-9492-4563-8681-AD288FA52ACE

processing....