Patellofemoral Osteoarthritis: Foot Characteristics and Interventions

Submission note: A thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy to the La Trobe Sport and Exercise Medicine Research Centre, School of Allied Health, Human Services and Sport, College of Science, Health and Engineering, La Trobe University, Victoria, Australia.

Thesis with publications.

Patellofemoral (PF) osteoarthritis (OA) is present in half of people with knee pain over 40 years of age and is associated with significant pain, functional limitations and reduced quality of life. The Osteoarthritis Research Society International (OARSI) recommends non-surgical interventions for the primary management of all knee OA. However, little is known of the etiological and functional characteristics of PF OA and consequently, effective non-surgical treatment options are currently limited. This thesis aimed to begin to address these deficits in our understanding of PF OA. As PF OA and PF pain in younger people (PFP) present with similar clinical features, Part A of this thesis explored the possibility of a disease continuum between the two conditions. Part B of this thesis then explored lower limb function and foot and ankle characteristics of people with PF OA. Finally, Part C aimed to determine the feasibility of conducting a clinical trial into foot orthoses and footwear interventions found to be beneficial in younger cohorts with PFP, and whether these interventions have potential to improve pain, function and quality of life in people with PF OA. Part A: Continuum of disease between PFP and PF OA, a narrative review: To address the aim of Part A, a narrative literature review was conducted to determine if younger people with PFP may exhibit similar structural and functional characteristics to older individuals with PF OA. With advances in medical imaging, early signs of OA have now been identified in those with PFP, providing support to the supposition of a disease continuum between PFP and radiographic PF OA. This review then explored whether similar variations in lower limb structure or function was present in the two conditions. However, a dearth of information regarding variations in lower limb structure and function in those with PF OA, particularly with regards to foot and ankle region, was identified. Considering that interventions targeting the foot are effective at improving Page | ii pain and function in those with PFP, this review highlighted the need to understand impairments in foot and ankle characteristics in those with PF OA, as they may serve to be effective targets for conservative interventions. Part B: Insights into lower limb function and foot and ankle characteristics of people with and without PF OA, consisted of 3 independent studies. To provide insight into what foot and ankle characteristics are associated with knee function, Part B-Study 1 explored the relationship between foot and ankle characteristics and lower limb function in younger healthy individuals, unaffected by pain or age-related changes in lower limb function. It was determined that higher foot mobility and lower ankle range are associated with a larger dynamic knee valgus, a feature commonly associated with PFP. Part B-Study 2 explored differences in foot and ankle characteristics between older healthy individuals and those with PF OA. It was determined that people with PF OA have greater foot mobility, which is similar in magnitude to the greater foot mobility seen in people with PFP. Finally, Part B-Study 3 provided preliminary evidence of altered neuromotor control in those with PF OA during stair ambulation – an activity which commonly causes PF pain. The findings of Part B provide evidence that: i) foot and ankle characteristics are associated with greater dynamic knee valgus; ii) foot and ankle characteristics are different in individuals with PF OA compared to similar aged healthy controls but similar to those with PFP, and; iii) foot and ankle characteristics are potential distal targets for non-surgical clinical interventions in PF OA. Part C: The effectiveness of foot orthoses and footwear in people with PF OA. The final section of this thesis comprised a pilot randomized controlled trial in 46 people with PF OA. This trial aimed to determine the feasibility of a full-scale clinical trial, and to explore if foot orthoses and prescribed footwear were superior to prescribed footwear alone in improving pain and function in those with PF OA. While a full-scale trial isfeasible with modifications to eligibility criteria, the strong positive within-group results for both interventions, and lack of large between-group differences, suggest that a fullsbcale trial is unlikely to find any major clinical differences between the interventions. It was Page concluded that prescribed footwear, with and without foot orthoses, is a promising intervention in people with PF OA and warrants further investigation. In conclusion, Part A of this thesis proposed that PFP and PF OA form a disease continuum based on similar clinical presentations between the two conditions, and explored similarities in structural and functional characteristics between PFP and PF OA. Part B demonstrated that similar foot impairments were present in both conditions, while also exploring how foot and ankle characteristics may impact on knee function. Part C provided evidence indicating that interventions effective in PFP may result in pain reductions, functional and quality of life improvements in people with PF OA. While further research is required, this thesis provides some of the first evidence regarding the structural and functional characteristics of PF OA and supports the likelihood of a disease continuum between PFP and PF OA.