Foot orthoses versus hip exercises and the effect of greater foot mobility in the management of patellofemoral pain

The patellofemoral joint comprises of an articulation of the patella with the trochlear groove of the femur. The patella is tethered distally via the patella tendon, proximally via the quadriceps tendon and multiple local structures such as medial and lateral patellofemoral ligaments retinaculum. When the knee flexes and extends, the patella engages and translates through the groove, often under high stress, during complex multidirectional motion. Patellofemoral pain (PFP) is a prevalent and recalcitrant knee pain condition that can have a significant impact upon a person’s quality of life. Patellofemoral pain is defined as anterior, retro and/or periarticular pain around the patellofemoral joint that is typically aggravated by weight bearing activities with a flexed knee. Patellofemoral pain is considered to be a multifactorial condition with various biomechanical, neurological and/or psychological contributors proposed in its aetiology. Due to its multifactorial nature, PFP can be an enigmatic condition for clinicians to treat. Various approaches targeting structures and areas local, distal and proximal to the patellofemoral joint have been proposed. As such, clinicians can become confused about what interventions are most effective for a particular patient. Two evidence-based recommended treatment approaches for PFP are foot orthoses and hip exercises. Foot orthoses and hip exercises have been investigated in clinical trials with each treatment having a proposed biomechanical mechanism of effect at the patellofemoral joint. However, these two treatments have not been compared head to head, to determine if either treatment is superior. Whilst the treatments have been shown to be effective, they are not a one-size-fits-all approach with results from clinical trials suggesting the presence of subgroups that reported a more favourable outcome to a particular treatment. Clinical guidelines recommend using evidence-based treatments that are tailored to the individual patient, however, there is a dearth of guidance on how to tailor the treatments. Furthermore, there is a paucity of evidence on how to identify the unique subgroups that might benefit most from a specific treatment. There was a need for further research to (i) determine if and what patient characteristics identify those with PFP who would benefit most from a specific treatment, and (ii) compare the clinical superiority of foot orthoses versus hip exercises.The chapters within this thesis explore the evidence and describe the design, implementation, and results of a randomized clinical trial. Study one was a systematic review of the literature. Preliminary evidence suggested greater midfoot width mobility (at least 11mm change in the width of the midfoot moving from non-weight bearing to weight bearing) was associated with greater global improvements with foot orthoses treatment. Crucially, the evidence was limited by studies lacking a comparator treatment and overfitting of variables for the statistical models. The review indicated that further research was needed to explore the potential treatment effect modification midfoot width mobility may have with regards to foot orthoses. Based on this preliminary evidence, study two was the design of a two-arm parallel; superiority randomised clinical trial in Australia and Denmark to address two aims. The aims were to test (i) the potential treatment effect modification of greater midfoot width mobility for foot orthoses treatment over hip exercises, and (ii) the clinical superiority of foot orthoses versus hip exercise treatments for managing PFP. The trial required the recruitment of 220 participants (18-40years) who reported an insidious onset of knee pain (≥6 weeks duration); that was aggravated by activities (e.g. stairs, squatting, running), and at least three out of ten pain on the numerical rating scale (ten being worst imaginable pain). Participants were stratified by their midfoot width mobility (high ≥11mm change in midfoot width) and site, and then randomised to foot orthoses or hip exercises. The primary outcome was a patient-perceived global rating of improvement at 12 weeks. Study three was the implementation of the randomised clinical trial. Of the 218 participants recruited and enrolled from June 2014 to April 2017, 192 completed follow up at 12 weeks. We found no difference in success rates between foot orthoses versus hip exercises in those with high midfoot width mobility (6/21 v 9/20; 29% v 45% respectively) or low midfoot width mobility (42/79 v 37/72; 53% v 51%). There was no association between midfoot width mobility and treatment outcome (Interaction effect P=0.19). This study found no difference in success rate between foot orthoses versus hip exercises (48/100 v 46/92; 48% v 50% respectively). The discovery that those with patellofemoral pain and greater foot mobility did not have superior benefits using foot orthoses, compared to hip exercises contradict common clinical assumptions. We found that foot orthoses and hip exercises offer similar global outcomes in the management of patellofemoral pain. These results suggest that clinicians should not use midfoot width mobility to decide which patients would benefit from foot orthoses, versus hip exercises. Given both foot orthoses and hip exercises offer similar global benefits, clinicians and patients can consider either in managing patellofemoral pain. Study four highlights a clinical case of a person with PFP. The person met the exclusion criteria for the trial as she had done briefly hip exercises as part of a fitness program in the last 12months. The case provides a clinical exemplar of the evidence, and reasoning, in the management of someone with PFP which may be clinically useful for similar case presentations. The case demonstrates the research in action and explores one avenue of tailoring treatment to the individual. Whilst the limitations of a case study are acknowledged, it offers hypotheses about relationships between physical, psychological, social and behavioural variables that remain to be investigated for PFP. Overall, the research in this thesis, and published studies, adds to the evolution of knowledge and clinical management of PFP. A potent outcome from this study showed both foot orthoses and hip exercises offer comparable benefits and needn’t select patient characteristics for one or the other on current evidence. This research opens path for foundations on future research on the beneficial effects of combining foot orthoses and hip exercises, cost-benefit analysis of interventions for PFP, and consideration for a stepped-approach to the management of PFP that includes an educational and activity modification aspect.