Date of Award

December 2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Health Sciences

First Advisor

Jennifer E Earl-Boehm

Committee Members

Monna Arvinen-Barrow, Wendy Huddleston, David Bazett-Jones, Paola Dey

Keywords

biopsychosocial, movement retraining, patellofemoral pain

Abstract

Patellofemoral pain (PFP) is a chronic pain condition of the knee that afflicts approximately 25% of the population, and may lead to long-term complaints of pain and dysfunction. In the current literature, PFP is primarily studied using the framework of the pathomechanical model of biomechanical and muscular factors that increase patellofemoral joint loading. However, PFP may be better understood examining it through the Biopsychosocial Model of Sport Injury Rehabilitation (Brewer et al., 2002) as a conceptual framework to explore how injury characteristics, sociodemographic factors, and intermediate biopsychosocial outcomes may impact a patient’s perceptions of pain and function. These relationships may also have in impact on treatment for PFP, as both the perception of pain and perception of function are commonly used as clinical outcomes to determine progress and prognosis. While there are several interventions that have been examined and implemented to treat patients with PFP, the long-term prognosis remains poor, with patients reporting symptoms months or even years after diagnosis. One treatment approach that is effective in both changing patient’s perceptions of pain and function as well as their biomechanics is gait retraining. This approach, based on the concepts of motor learning, is commonly performed during running gait. Not all individuals with PFP are runners or may select not to run due to their knee pain. There is limited evidence to suggest that the concept of movement retraining applied to more universal tasks, such as a step-down, could yield similar results. Within the context of the Biopsychosocial Model (Brewer et al., 2002), the intervention chosen for the treatment intervention, along with delivery of that intervention by a trained health care professional, are components of the rehabilitation environment. The rehabilitation environment is one of many social and contextual factors within the Biopsychosocial Model (Brewer et al., 2002) that may impact the patient’s perceptions of pain and function, as well as the intermediate rehabilitation outcomes. Therefore, using the Biopsychosocial Model (Brewer et al., 2002) as a conceptual framework, the purpose of this study was two-fold: 1) to better understand how selected injury characteristics (duration of symptoms and location of pain), sociodemographic factors (gender and age), and intermediate biopsychosocial outcomes (hip and knee strength and trunk, hip and knee biomechanics) relate to participant’s perceptions of pain and function, and 2) to assess how a squat retraining intervention changes a participant’s hip and knee strength, trunk, hip, and knee biomechanics, and perceptions of pain and function in individuals with PFP. Three separate studies were conducted to achieve the study purpose. Study 1 consisted of a cross-sectional, U.S. population-based online survey shared via social media, email, and word of mouth to adults (18-45 years) with knee pain. Out of 400 respondents, 243 participants completed all four components of the survey, and 137 (105 females, 32 males, 30.80+8.68 years) were identified as having PFP. Duration of symptoms, location of pain, gender, age, perception of pain, and perception of function were assessed with the online survey. A multinomial logistic regression was utilized to create a model of the relationship between the independent variables and perception of pain score. A multiple linear regression was used to create a model for the relationship of the independent variables and perception of function score. Study 2 was a cross-sectional study conducted in a laboratory, with 40 participants (30 females, 10 males, 33.9+7.5 years) with PFP. Perceptions of pain and function, isometric hip and knee strength, and trunk, hip and knee 3-D kinematics and 2-D biomechanics during a step-down task were assessed. Pearson correlations were performed to determine if relationships existed among any of the variables. Separate multiple linear regressions were used to create a model of the relationship between all of the strength and biomechanical variables and perceived pain and function. Study 3 was a feasibility study consisting of 10 participants (9 females, 1 male, 36.30 + 6.48 years) using a novel movement retraining intervention aimed at correcting knee alignment during a step-down. Wilcoxon Signed Rank tests and paired t-tests were performed to determine differences from baseline to post-intervention for perceived pain and function, hip and knee strength, and the biomechanical variables. A summary of the results is presented here, with full statistics in each respective chapter. In Study 1, individuals who had PFP for a longer period of time, experienced widespread pain, and reported higher perceptions of pain also reported lower perceptions of function. Age and gender were not related to perceptions of pain or function in our sample. In Study 2, perception of pain was significantly correlated with perception of function and hip internal rotation (IR) angle, while perception of function score was significantly correlated with the perception of pain, hip abduction (ABD) strength, hip external rotation (ER) strength, knee extension (EXT) strength, and 2-D lateral trunk motion (LTM). For Study 3, perception of pain changed significantly from baseline to post-intervention and LTM significantly improved from baseline to post-intervention. Results of this study support that symptom duration and painful locations are related to the perception of function in individuals with PFP. It emphasizes the need for early identification and treatment of PFP to minimize pain and preserve function early in the course of the overuse injury. We did not find a statistically significant predictive relationship between hip and knee strength and trunk, hip, and knee biomechanics and participant perceptions of pain and function in our sample. This suggests that there may not be a specific pattern of movement or muscle weakness that is uniform across individuals with PFP. Rather, the experience of PFP may be more individualized. The movement retraining intervention piloted in this study was effective at improving perceptions of pain, even though it did not lead to significant changes in strength or biomechanics, or perception of function. Taken together, these results provide preliminary support for the Biopsychosocial Model (Brewer et al., 2002) to be used as a framework to examine the overuse injury of PFP.

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