Physiological mechanisms and clinical efficacy of comfortable in-shoe foot orthoses in the short-term treatment of anterior knee pain

In-shoe foot orthoses are frequently used by clinicians in the prevention and treatment of a variety of lower limb overuse injuries, including anterior knee pain (AKP). Despite a nascent body of evidence and widespread clinical use, the mechanism(s) underlying their efficacy remains a topic of conjecture. Presently, kinematic alteration, shock attenuation and neuromotor adaptation are the 3 main paradigms used to explain the effects of orthoses; however individual variation is often reported to be greater than any systematic effect. Potentially due to this observed variation, there is increasing attention on comfort as a key consideration in orthosis prescription. On a prima facie basis it is evident that uncomfortable orthoses are less likely to be worn, which defeats the purpose of prescribing them. Few studies to date base orthosis prescription wholly on comfort and most investigate physiological mechanisms in asymptomatic individuals or groups reporting a range of lower limb injuries. Establishing a reliable comfort measure would assist clinicians in orthosis prescription. Investigating the physiological mechanisms for orthoses with proven clinical effect would facilitate improved knowledge in how orthoses are efficacious in an AKP population. Thus the primary aim of this thesis was to investigate the physiological mechanisms and clinical efficacy of comfortable prefabricated orthoses in people with AKP. This was addressed by conducting a systematic review of potential physiological mechanisms, investigating measures of footwear comfort and their role in orthosis prescription and conducting a randomised control trial examining immediate physiological adaptations and short-term clinical efficacy of orthoses. The systematic review analysed the effect of orthoses with different design features (posting, moulding and density) within the identified paradigms of kinematic adaptation, shock attenuation and neuromotor adaptation. Meta-analysis of kinematic data identified medially posted orthoses, without moulding, produced relatively small (~ 2°) but systematic reductions in peak rearfoot eversion and tibial internal rotation in asymptomatic individuals. In contrast, orthoses that were moulded produced large reductions in loading rate and vertical impact forces compared with controls and posted non-moulded devices. Results from the neuromotor paradigm were the least conclusive and suggest that injury history may influence the effects of orthoses. Results from this review highlighted the need for further investigation, particularly within the neuromotor paradigm, of currently injured individuals displaying a single injury type. In order to prescribe orthoses based on comfort, important initial steps were to identify the most reliable footwear comfort scale and identify a clinically meaningful change in comfort and important comfort dimensions. To do this, a ranking scale, visual analogue scale (VAS) and Likert scale were compared over 5 consecutive days. Of the 3 scales, a ranking scale was found to be the most reliable scale. A 100 mm VAS was also found to be reliable but only after 2 consecutive days. From VAS data, overall comfort, forefoot cushioning, arch cushioning and arch support were identified as important comfort dimensions and a change of 10.2 mm was found to indicate a clinically important change in comfort. When the ranking scale and VAS were applied to orthoses it was observed that changes exceeding this amount were required to change the orthoses’ comfort relative to the usual shoe in an asymptomatic cohort. In this cohort, flat-soft orthoses were found to be significantly more comfortable than contoured orthoses, with no difference in relative comfort of orthoses observed between walking and jogging. The final component of this thesis was a randomised control trial to assess the clinical efficacy of comfortable prefabricated orthoses in people with AKP. Baseline comparisons of 4 orthoses that differed in relative comfort were used to investigate immediate neuromotor and kinematic effects. When all orthoses were compared to the individuals’ usual jogging shoe, no immediate physiological adaptations were observed. When perceived comfort and midfoot mobility were considered, it was found the least comfortable orthosis produced larger physiological alterations compared with more comfortable designs. A greater adaptation when comparing differences between the shoe and least comfortable orthoses was observed in hip adduction in individuals with a more mobile midfoot (>10.96 mm) compared to all other orthoses and individuals with a less mobile midfoot. The least comfortable orthosis increased vastus lateralis peak amplitude compared with the shoe and the most comfortable orthosis, regardless of midfoot mobility. As both of these alterations are reported to be factors contributing to AKP, more comfortable orthoses are advocated. Regarding short-term clinical efficacy, comfortable orthoses were found to be more efficacious than a wait-and-see approach in terms of global improvement and function. In addition, it was observed that individuals with midfoot mobility of >11.25 mm were more likely to succeed with orthosis treatment. The findings from the baseline analyses and the primary outcome of randomised control trial when taken together suggest comfortable orthoses produce minimal disruption to the preferred movement path and proximal lower limb muscle activation patterns, as well as improving AKP after 6-weeks, especially in those individuals exhibiting a mobile midfoot