Painful knee osteoarthritis is common and treatments, short of knee replacement, are limited. The investigators plan to test the efficacy of a novel promising device for treatment of knee osteoarthritis affecting the inner part of the knee, the most common location. There are no disease modifying treatments available and therefore there is an emphasis on conservative management techniques to benefit individuals. Many of these treatments (insoles, braces, physiotherapy etc) have been shown to have relative success in individuals but a new novel device is demonstrating better effectiveness in this patient group. APOS (All Phases of Step) therapy consists of a shoe oriented system of care that works by shifting the load across parts of the knee and retraining the lower extremity muscles. Preliminary data suggest impressive favourable reductions in knee pain and a commensurate decrease in knee loading during walking. However, APOS treatment has never been evaluated in a randomised controlled trial even though it is widely used. The investigators propose to conduct a randomised blinded controlled trial of APOS treatment among persons with painful knee osteoarthritis affecting the inside (medial or lateral) of their knees. The investigators will focus on pain outcomes and quality of life. APOS has committed to provide the shoe system and a matched sham device, that they have developed, and will also provide the technicians trained to calibrate the pertupods (balls under the sole of the foot) on the shoe without charge. The research will be undertaken in a University setting for the gait evaluations.

Background

Osteoarthritis (OA) is the most common arthritic condition and is one of the leading causes of disability in adults in Switzerland and worldwide (CDC 2009, WHO 2004). With the steady escalation of world life expectancy and constant decline in world birth rates, the incidence and prevalence of OA are expected to rise continuously worldwide throughout the years to come (Badley 1998). In Switzerland, OA is associated with decreased quality of life and frequent use of the health care system (Rosemann 2008).

Currently, no treatment can stop or reverse the progressive joint degeneration caused by OA. Most clinical interventions aim to improve pain and disability as these are the main symptoms afflicting OA patients (Grotle 2008), but managing pain associated with OA of the knee is difficult. Existing non-pharmacological and pharmacological interventions for OA remain insufficient. There are few effective nonsurgical treatments for painful knee OA (Jüni 2006).

OA affects different compartments in the knee, and biomechanical factors play an important role. Observational studies suggest that approximately 60% of affected persons have medial joint involvement (Niu 2009), which is subjected to excessive loading as quantified by the adduction moment across the knee. Bone marrow lesions (BMLs) are seen in knees in most persons with painful knee OA on fat suppressed MRI images. In the MOST cohort study, 80% of persons with medial knee OA and knee pain had medial BMLs. On histology, BMLs represent areas of bone damage with micro-cracks and remodelling. They are strongly related to malalignment such that knees with varus alignment have a high risk of BMLs in the medial compartment and those with valgus alignment have a risk of lateral BMLs (Felson 2003).

Wedges and orthotics which realign the knee have been tested in several randomized trials. This literature has undergone a Cochrane review of orthoses for treating knee OA (Brower 2005) which noted in its conclusion that, 'wearing a laterally wedged orthosis compared to wearing a neutral wedge may not lead to any difference in pain, knee function, or overall well-being'. None of the trials testing orthotics and inserts have shown any significant effect compared to control in terms of knee pain reduction. The other notable finding of almost all of these trials is that they reduced the varus moment across the knee, but by only 6% on average. One possible reason why inserts and orthotics have not worked to reduce pain is that they do not have a large enough realigning effect on the knee (as assessed by the varus moment).

APOS therapy, a new popular medical device, is a shoe system demonstrating potentially improved effectiveness in patients suffering from OA. This footwear has two potential mechanisms of action: 1. it can alter the pattern of knee loading, with reported reductions in the varus moment of 17% (Elbaz 2010), and 2. it retrains lower extremity motor control. Forcing people to avoid walking on the usual wide plantar surface and to instead walk on two rubber balls (APOS shoe) for half an hour at the start of the study, increasing successively (+10 min/week) up to almost 5 hours/day after 24 weeks (not exactly according to scheme but at the physiotherapist's discretion), forces muscular retraining and therefore serves as a built-in exercise intervention.

The investigators therefore aim to compare the efficacy and safety of APOS therapy in a large, pragmatic randomized controlled trial that includes gait analysis to understand the mechanistic action of the device.

Objective

Overall objective: The purpose of this trial is to evaluate whether APOS therapy can improve symptoms compared to Sham APOS therapy in participants with symptomatic knee OA.

Primary objective: The trial will determine the effect of APOS therapy on pain compared to Sham APOS therapy after 24 weeks.

Secondary objective: Secondary objectives will be to determine

• The effect of APOS therapy on pain compared to Sham APOS therapy after 4, 8, 12 and 16 weeks
• The effect of APOS therapy on joint stiffness, disability and overall assessment of the disease compared to Sham APOS therapy after 4, 8, 12, 16, and 24 weeks
• The effect of APOS therapy on quality of life after 4, 8, 12, 16, and 24 weeks
• The effect of APOS therapy on gait analysis measurements at baseline, after 4, 8, 12, 16 and 24 weeks
• The effect of APOS therapy on rescue analgesics compared to Sham APOS therapy throughout study duration (24 weeks) and after 24 weeks
• The time spent on average in the shoe

Methods

This trial is a patient-blind, single-centre, two-arm, parallel-group, 24 weeks (6 months) randomized controlled trial comparing APOS therapy and Sham APOS therapy. While the patients and physicians will be blinded regarding the intervention, the technician applying the shoes will not.

The trial will be conducted among persons with painful knee osteoarthritis. 220 patients will be randomly assigned on a 1:1 basis to one of the two treatments, APOS therapy or Sham APOS therapy. Randomisation will be stratified according to lateral / medial and unilateral / bilateral knee OA status.

Inclusion Criteria:

• Men or non-pregnant women
• Aged >= 40
• Outpatient setting
• ACR clinical criteria for OA of the knee
• Radiologically confirmed symptomatic uni- or bilateral OA of the knee for at least 6 months
• Radiological criteria: X-rays showing tibiofemoral knee osteoarthritis defined as at least Kellgren and Lawrence Grade 2
• At least moderate pain on the WOMAC pain scale (>3 on a standardized scale range from a minimum of 0 to a maximum of 10)
• Must understand German
• Informed Consent documented by participant signature

Exclusion Criteria

• Pregnant women
• Aged < 40
• History of an inflammatory rheumatic disease
• Non-knee musculoskeletal pain as or more severe than the knee pain
• Glucocorticoid injections in the knees in the previous three month
• Previous osteotomy
• Unilateral hemiprosthesis
• Unilateral total joint replacement
• Being treated for cancer
• Participation in another clinical trial