Full length articleWhich is the best predictor of excessive hip internal rotation in women with patellofemoral pain: Rearfoot eversion or hip muscle strength? Exploring subgroups
Introduction
Patellofemoral pain (PFP) is a common complaint amongst sports medicine clinics, accounting for 25–40% of all knee injuries [1]. It has been reported that women are more likely to experience this condition than men [2]. Clinically, individuals with PFP report limitations in activities that load the patellofemoral joint (PFJ) during weight bearing on a flexed knee [3], especially ascending stairs [4]. Furthermore, the impact of PFP as a medical issue is highlighted by evidence suggesting a chronic and recurrent nature of pain, persisting for many years with unfavorable outcomes after rehabilitation [5].
The source of pain in individuals with PFP remains unclear [3]. However, the most recent consensus statement from the 4th international PFP retreat proposed a pathomechanical model in which the development of PFP is associated with increased PFJ stress. One of the theories indicate excessive hip internal rotation during weight bearing activities as a possible source of increased PFJ stress [[6], [7], [8]]. There are two well-known theoretical models which attempt to explain the cause of excessive hip internal rotation in women with PFP [[9], [10]]. One assumes that the hip joint depends on hip muscles to provide dynamic stability and control the movement of the femur, therefore, reduced hip strength may lead to a poor hip control and result in an excessive hip internal rotation [9]. Lower isometric, concentric and eccentric hip abductor strength have been reported in women with PFP [[11], [12], [13]]. Specifically, lower concentric hip abductor strength may be associated with excessive hip internal rotation during stair ascent. In this activity, predominantly concentric contractions of hip abductors are required to control the hip movement [[14], [15]]. Another theoretical model assumes that excessive rearfoot eversion during the stance phase of gait [16] or stair ascent [4] may result in excessive hip internal rotation due to joint coupling [10].
Considering the need to reduce PFJ stress, knowing the mechanism that is more associated with hip internal rotation could help clinicians to identify the best treatment strategy to individuals with PFP. For instance, if the lower hip abductor strength is more associated with hip internal rotation, strengthening the hip abductor muscles could be an option to avoid increased PFJ stress in women with PFP. On the other hand, if the excessive rearfoot eversion is more associated, foot orthoses prescription could be also performed in order to avoid the increased PFJ stress [17].
In this context, the aim of this study was: (i) to investigate if the peak rearfoot eversion during stair ascent and/or the peak concentric abductor muscle strength can predict peak hip internal rotation during stair ascent in women with PFP.
Section snippets
Participants
Thirty-seven women with PFP aged 18 to 35 years were recruited between September 2016 and May 2017 via advertisements at fitness centers, public places for physical activity and social medias. The study was approved by the Local Human Ethics Committee, and all participants provided written informed consent. The diagnostic criteria for PFP is listed in Table 1.
Procedures
Demographic data (age, body mass and height) were collected prior to testing. All participants were asked to rate their worst knee pain
Results
Descriptive values of participant’s demographics, self-reported measures of pain, function and duration of symptoms, kinematics and strength variables are presented in Table 2.
Peak concentric hip abductor strength significantly predicted peak hip internal rotation during stair ascent (R2 = 0.27, B = −0.05, 95%CI −0.08 to −0.02, p = 0.001). Peak rearfoot eversion did not predict peak hip internal rotation during stair ascent (R2 < 0.01, B = 0.12, 95%CI −0.40 to 0.65, p = 0.62) (Fig. 2).
Discussion
Our findings indicate that only peak concentric abductor strength explained significantly the variance of peak hip internal rotation during stair ascent in all women with PFP. However, after splitting the participants into subgroups regarding excessive or non-excessive rearfoot eversion, we found that in the excessive rearfoot eversion subgroup, both independent variables (peak concentric abductor strength and peak rearfoot eversion) significantly predicted the variance of peak hip internal
Conclusion
In general, peak concentric hip abductor strength and not peak rearfoot eversion predicted peak hip internal rotation while ascending stairs. However, in a subgroup with only women with excessive rearfoot eversion (48.6%), peak concentric hip abductor strength and peak rearfoot eversion predicted the peak hip internal rotation while ascending stairs.
Conflict of interest
No author has any financial or personal relationship with people or organizations that could inappropriately influence this work.
Acknowledgments
To São Paulo Research Foundation (FAPESP) for a grant (2014/24939-7) and a scholarship (2016/02357-1). The financial sponsors played no role in the design, execution, analysis and interpretation of data, or writing of the study.
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Present address: La Trobe University, School of Allied Health, Bundoora, Victoria, Australia.