Dr Neil Craig
RE: 84 year old female first seen on 30/10/2014 at Narrabeen Sports Medicine Centre, Sydney
This patient presented with 4 months of progressive bilateral medial knee pain, described as an ache of gradual onset with sharp exacerbations up to a severity of 8/10 in the left knee during weight-bearing. There were no mechanical symptoms.
Her medical history included a partial medial meniscectomy of the right knee in 2001 and the left knee in 2005.
The patient stopped playing representative netball in her mid-20s and has done little exercise since. She was concerned that she required joint replacements but believed she was not fit for surgery.
Her medication included Mobic 15mg, Omeprazole 10mg, Simvastatin 40mg and Aspirin 75mg.
On examination, the following significant findings were noted:
- The patient was obese (BMI 39.4 kg/m2).
- There were bilateral knee effusions and a tender popliteal cyst in the left knee.
- Range of motion was 5° - 135° in the right knee and 12° - 116° in the left knee restricted by pain.
- There was significant crepitus in the medial compartment of both knees.
- There were no mechanical signs but there was pain on loading the medial compartments of both knees.
Medial knee pain and swelling can be caused by osteoarthritis, rheumatoid arthritis, gout, meniscal tears, Baker’s cysts, medial plica syndrome and pes anserine bursitis.
Plain X-rays showed loss of medial joint space with some osteophytes more pronounced on the left knee.
The patient was diagnosed with progressive medial compartment osteoarthritis, with an inflammatory component causing a joint effusion and popliteal cyst.
Factors Contributing to the Diagnosis
Osteoarthritis (OA) is the most common cause of disability in the older population. The prevalence in the United Kingdom of painful osteoarthritis of the knee in those over 55 years old is 10%, of which 25% would consider themselves severely disabled. With an ageing population, the prevalence of OA is expected to increase.1
OA has a multifactorial aetiology with systemic and local risk factors. Many of these are non-modifiable, including age, gender, and genetics, and many are modifiable.2 Therefore, interventions exist which may prevent or delay the onset of the condition. As Obesity has long been recognised as the single most important modifiable risk factor for osteoarthritis of the knee2, and is a large topic in its own right, this will be the primary focus of this case discussion.
Obesity as a risk factor for Osteoarthritis
Obesity has been the focus of many studies evaluating causes of osteoarthritis of the knee, with a recent meta-analysis reporting 36 papers analysing the effect of BMI on osteoarthritis. Although the effect sizes were variable, all of them found that being overweight or obese was a significant risk factor for the development of knee osteoarthritis (Pooled Odds Ratio 2.96; 95% Confidence Interval: 2.56, 3.43). Some studies reported gender-specific results which found greater effect sizes for obesity in women than those in men.2
The traditional explanation for obesity as a risk factor for OA has involved the increased mechanical load on the joint from adipose tissue. Over time, a more complex and multifactorial theory has evolved, linking excessive fat accumulation and relative loss of muscle mass with the release of a range of pro-inflammatory mediators including adipokines, interleukin-1β, cyclooxygenase-2, prostaglandin-E2 and matrix-metalloproteinase-2. Furthermore, interleukin-6 and C-reactive protein have both been shown to predict the incidence and progression of arthritis.3
Obesity results from the interplay between many variables, including biology, physical activity (PA) and eating behaviour within an environmental, cultural and social landscape. This is depicted in the obesity system map (Figure 1).4 Although extremely complex, at the core is central energy balance driven by 4 key variables and intervention points: primary appetite control, dietary habits, level of PA, and psychological ambivalence. The degree of appetite control in the brain controls the biological appetite and energy expenditure relationship, and covers the physiology cluster of the map. Dietary habits often keep individuals from adopting healthier alternatives, and cover the food section of the map including calorific content and portion size. An individual’s physical activity level is the most important modifiable method of energy expenditure in the activity section of the map, and finally the psychological aspect of the map covers many motivations and social drivers on individual, family and societal behaviours regarding lifestyle choices.4
(Figure 1: Obesity System Map – The central energy balance engine is influenced by psychological, activity, physiology, and food factors.)
Government Office for Science and Department of Health. Tackling Obesity: Future Choices.4
One high quality study involved 473 individuals and concluded that 5kg of weight loss reduced the risk of OA by over 50%, and a weight loss of 1 kg/m2 reduced male symptomatic OA by 21.4% and female symptomatic OA by 33%.5 These results clearly demonstrate the benefit of weight loss for preventing osteoarthritis, and as a treatment for osteoarthritis.
Opinion and evidence for the best method of weight loss is variable. While a calorie-restricted diet is important, maintenance of daily nutrients such as calcium is essential for the elderly, and for many obese patients compliance with long-term lifestyle changes is low.3 However, exercise can help to reduce weight, strengthen the muscles around the knee, and reduce pain and disability. Some studies have highlighted combined exercise and diet therapy showing greater improvements in knee pain and physical function than exercise or diet alone.3
Brief primary care interventions vary from basic advice to focussed discussions around factors influencing levels of activity. The Physical Activity and Health Alliance have published a number of tools to facilitate such interventions, in particular the Scottish Physical Activity Screening Question (Scot-PASQ - Appendix 1) used to assess current activity level and readiness for behaviour change.6 Physical Activity Brief Advice and Brief Intervention Scripts (Appendix 2) also provide a format for these discussions7, and are included as part of the GP Quality Outcomes Framework (CVD-PP003) for the primary prevention of cardiovascular disease.8
Current recommendations for older adults (Appendix 3) are for daily PA, totalling 150 minutes/week of moderate intensity activity, including muscle strengthening activity at least twice per week.9 Although walking, climbing stairs and running are recommended, these are load-bearing activities which may exacerbate osteoarthritis. Therefore, partial and non-weight bearing activities including water-based wading, deep-water running and freestyle kicking with flippers may be more appropriate. Resistance activities, such as drop-squats and calf raises, should also be included.10 Physiotherapy supervision and swimming pool membership may help to maintain compliance.
Formal exercise referral schemes also exist which may maintain compliance and initiate behaviour change. In Scotland, sedentary patients with existing health problems, including osteoarthritis, can be referred by a GP to a programme of free or subsidised exercise.11
Dietary interventions to aid weight loss require modifying the quantity, frequency and type of food to achieve a caloric deficit. This may be achieved by diet alone, or supplementation with PA. SIGN guidance describes a number of interventions including reducing energy intake, low calorie diets and commercial diets. SIGN have produced criteria to assist practitioners in advising patients on these programmes in adults (Table 1).11
Table 1: Best practice guidelines for weight management programmes11
Application of Obesity Interventions
Moderate evidence from 15 studies suggests an increase in PA levels in those who received brief advice. However, there is also evidence that practitioners consider a lack of materials, incentives, time, knowledge and confidence as a barrier to discussing or prescribing physical activity.12 Therefore, an early brief intervention from this patient’s GP may have enabled her to increase her activity levels and reduce her weight, delaying or preventing the onset of her knee OA. However, a lack of support and materials for her GP may have influenced this, and an improvement in these resources could improve brief physical activity interventions.
There is variable evidence for the effectiveness of exercise referral schemes, with 2 RCTs reporting a positive effect on PA levels in 6 – 12 weeks, but 4 trials have shown that such schemes are ineffective over one year.12 Therefore, a brief intervention may initially have been more appropriate to encourage the patient in this case to lose weight, but if this was ineffective then a trial of an exercise referral scheme could have been considered.
Studies have shown that the recommended 0.5 kg of weight loss per week results from an energy deficit of 500 kcals per day. Reducing energy intake, up to a maximum of 600 kcal/day, were shown in an analysis of 12 studies to produce a median weight change of 4.6 kg. Low and very low calorie diet analysis included patients who consumed 800 - 1800 kcal/day and <800 kcal/day respectively, and were associated with 5 – 6% weight loss at 12 months. Very low calorie diets showed greater weight loss at 3 – 4 months but this was not maintained at 12 months.11
A number of commercial diets exist including Slim-Fast and WeightWatchers. One RCT found all such diets to be successful in losing weight (mean loss 5.9 kg) at 6 months. Participants who maintained the diet at 12 months sustained weight loss at 10% of their original weight.11 Therefore, this patient may have experienced some benefit by losing weight via dietary means. In particular, a calorie restricted diet may have been the optimum long-term measure, but in the short term a commercially available diet may confer considerable benefit. Such weight loss would reduce the impact of obesity on the development of her osteoarthritis.
This patient had a number of risk factors for the development of bilateral knee OA. However, her obesity is known to be the largest modifiable risk factor implicated in the pathogenesis of her disease2, which is due to the abnormal load placed upon the joints as well as the release of pro-inflammatory mediators.3 A number of interventions exist within the UK to increase physical activity levels and improve the dietary intake of patients.11 For this patient, appropriate exercise prescription involving partial and non-weight bearing exercise, as well as information regarding calorie-deficit and commercially available diets, may have prevented or delayed the onset of her OA.
- Peat G, McCarney R, Croft P. Knee pain and osteoarthritis in older adults: a review of community burden and current use of primary healthcare. Ann Rheum Dis. Feb 2001; 60(2): 91 - 97.
- Blagojevic M, Jinks C, Jeffery A, Jordan K. Risk factors for onset of osteoarthritis in the knee in older adults: a systematic review and meta-analysis. Osteoarthritis Cartilage. Jan 2010; 18(1): 24 – 33.
- Bliddal H, Leeds A, Christensen R. Osteoarthritis, obesity and weight loss: evidence, hypotheses and horizons – a scoping review. Obes Rev. Jul 2014; 15(7): 578 – 586.
- Government Office for Science and Department of Health (Foresight). Tackling Obesity: Future Choices – Project Report. 2nd Ed. London. Published Oct 2007. Available from: https://www.gov.uk/government/collections/tackling-obesities-future-choices
- Felson D. Weight and osteoarthritis. Am J Clin Nutr. Mar 1996; 63 (3 Suppl): 430S – 432S.
- NHS Health Scotland and the University of Edinburgh. Scottish Physical Activity Screening Question. Published Oct 2012. Available from: http://www.paha.org.uk/Resource/scottish-physical-activity-screening-que...
- NHS Health Scotland. Physical Activity Brief Advice and Brief Intervention Scripts. Published Oct 2012. Available from: http://www.paha.org.uk/Resource/physical-activity-brief-advice-and-brief...
- The Scottish Government and the British Medical Association (BMA). Quality and Outcomes Framework (QOF) Guidance for NHS Boards and GP Practices 2014/15. Cited 31/11/14. Available from: www.bma.org.uk/qofguidance
- Department of Health, Ellison J MP. Policy: Reducing obesity and improving diet. London. Published March 2013. Available from: https://www.gov.uk/government/policies/reducing-obesity-and-improving-diet
- Cochrane T, Davey R, Matthes Edwards S. Randomised controlled trial of the cost-effectiveness of water-based therapy for lower limb osteoarthritis. Health Technol Assess. Aug 2005; 9(31): 1 – 114.
- Scottish Intercollegiate Guidelines Network (SIGN). Guideline 115: Management of Obesity. February 2010. Available from: http://www.sign.ac.uk/pdf/sign115.pdf
- National Institute for Health and Care Excellence (NICE). NICE Public Health Guidance 2: Four commonly used methods to increase physical activity. Issued: March 2006; Last Modified: May 2013. Cited 07/12/14. Available from: http://www.nice.org.uk/guidance/ph2
Appendix 1: Scottish Physical Activity Screening Question (Scot-PASQ)
Appendix 2 – Physical Activity Brief Advice and Brief Intervention Scripts
Appendix 3: Physical Activity Guidelines for Older Adults