Advice can be given on prevention to try and limit high loading to the knee in sporting activities e.g. rugby, football and weight lifting. Patients in occupations such as in particular mining and farming have also previously been identified as being at risk. Body mass index attributes to joint loading and should also be a focus of attention. Usually at an early stage there is no pain. Consequently, exercise and weight control advice becomes secondary prevention. This includes a variety of exercise techniques, examples are listed in Additional file 1: Figure S1.
The evidence for physical activity
National Health Service (NHS) publications in 2009 'Let's get moving' and 'Be active, be healthy' both state that the British population is predominantly inactive [16, 17]. This correlates strongly with disease, health risk, economic costs, loss of functional earning capacity and premature mortality. This epidemiological relationship forms the basis for health commissioning. Evidence for individual treatment of chronic osteoarthritis is sparse, frequently because it is difficult to control confounding variables or separate overlapping treatment modalities. Treatment is always individualised to the diseased joint and multi-factorial. Assessment tools are invariably weak and are not universal.
In an extensive review by Pederson and Saltin from 2006, strength training combined with endurance training was advocated for osteoarthritis . Strengthening surrounding muscles enhances joint function and co-ordination, and endurance training helps with weight loss and general physical conditioning. The EULAR (European League Against Rheumatism) recommendations for knee and hip osteoarthritis separately outlined their own guidelines . These focused on general, non-pharmacological, pharmacological, surgical and combination therapies. Quality of data was expert opinion based, evidence based, or an amalgamation of both. Authors reviewed 1,447 citations of which only 21 met their criteria. The summary closely agreed with the American College of Rheumatism (ARC) guidelines from 2003 but they decided to keep the knee separate from the hip due to differences in risk factors, anatomy, treatment options and use of topical agents. A review by Petrella in 2000 regarding effective exercise treatment for osteoarthritis reviewed 23 trials, of which only three were considered sufficiently powered to draw conclusions . Petrella concluded that exercise programs should be offered to all patients as a mainstay of non-pharmacological management of knee osteoarthritis and that focusing on associated co-morbidities, in particular obesity, could also help with compliance. The typically responsive patient would present with mild to moderate osteoarthritis with limited function, pain and mild stiffness.
The evidence for promoting lifestyle change
Published articles have evaluated how to promote lifestyle change with motivational interviewing techniques . Jensen in 2003 suggested a self motivated pain management model . Somers in 2008 described reducing abnormal pain behaviour (catastrophising) and responses to treatment for knee osteoarthritis .
In 2003 Estabrooks, Glasgow and Dzewaltowski provided recommendations for physicians in the role of physical activity (PA) promotion [24
]. They surmised that the evidence was variable and not universally followed and they proposed the following principles. Firstly, intervention activity does not need to be time consuming nor senior-led. Secondly, patients need to be active participants in decision making, helping to develop these plans and strategies to overcome barriers and monitoring. Thirdly, feedback was critical and had to be specific. Finally, to ensure maintenance, intervention activity should be integrated into community opportunities wherever possible. The sequence of promotion in primary care was the five 'A's':
Assess the current level of physical activity, abilities, beliefs and knowledge
Advise on health risks, benefits of change, appropriate activity, its quantity and intensity
Agree a personal developmental plan with appropriate goals
Assist in identifying barriers and strategies to address these. Also to link in with community opportunities for activity and social support
Arrange follow-ups by telephone calls or letter.
A cross sectional study published in 2009 by Scopaz et al. clarified psychological factors and their influence upon physical function with 182 patients with knee osteoarthritis . They looked at anxiety, depression and 'pain fear' avoidance using a range of functional and psychological scores. Critically they used only one activity of daily life score and one generic lower limb joint pain and function score. Other tools exist which are more specific to the knee, which could have been used to improve validity and comparison.
Scientific literature from the last ten years identified seven randomised control trials (RCTs) concentrating on activity interventions for knee osteoarthritis. These have strengthened the case for activity intervention concentrating on all aspects for example hands-on treatment , primary care exercise advice , health education  and group versus home exercise . These studies also gave the impression of better results with longer intervention periods of attendance but the maximum study follow up was 18 months. Comparing all the RCTs relating to exercise and lifestyle interventions in knee osteoarthritis, significant variance existed in sample sizes, length of follow-up, assessment tools with often minimal description in disease severity.
In the 'Arthritis, Diet and Activity Promotion Trial', 206 patients were randomised into diet and exercise interventions over 18 months . Early compliance to dietary intervention occurred in isolated cases, following one advice session. Longer compliance with advice resulted from home exercise plans with single advice sessions. The authors concluded that compliance was related to a location of exercise and an emphasis on a stimulating early intervention session attendance.
The ARTIST (Osteoarthritis Intervention Standardised Trial) study concentrated on the impact of consultations by primary care rheumatologists in France . These patients had either three standardised consultations or normal treatment. At four months, both weight loss and physical exercise levels were significantly improved in the consultation group. At one year, function and pain levels were also improved. This study was well executed as it excluded significant co-morbidities and ensured osteoarthritis was the definitive diagnosis. The interventions were one-to-one and concentrated on self confidence, barriers, and methods of overcoming these and goal setting. The trial designers accepted that time was limited and, as such, communication had to be effective. Each of the three visits was therefore carefully controlled; the first visit concentrating on the disease and treatment with the second and third on exercise or weight loss in either order. The interview was motivational but not, however, clearly defined in the study. Advice regarding weight control did follow government published guidelines: the patient had to assess their own risk and be ready to lose weight and determine a programme and appropriate strategy. Numerous booklets were also provided to patients. The outcomes were independently determined. The study also formally studied appreciation and consequences to intervention as judged by knowledge retention which was improved in all cases, but clearly short-term. Limitations included the blinding of the study, the wish for matched groups but the control group had heavier patients and nine cases were excluded. Interestingly, the mean weight loss was only one kilogram at 4 months with no difference between groups at one year.
The social cost has also been studied by Sevick et al. in Pittsburgh . This was a single-blinded, controlled trial of 316 adults with knee OA, randomised to one of four groups: Healthy Lifestyle Control group, Diet group, Exercise group, or Exercise and Diet group. Combined exercise and dietary intervention demonstrated the greatest benefits in weight control, symptom control and physical function levels and also proved to be the most cost-effective strategy.
Three reviews have been published specific to influences of exercise on osteoarthritis of the knee [33–35]. They found that the short-term benefits of aerobic and strength training for pain and function are not borne out in the long term (greater than 6 months). They reiterated the comments above of the lack of clarity with a Cochrane review on musculoskeletal pain recommending standardised assessment tools and longer follow-ups to identify long-term strategies for physical activity in knee osteoarthritis.