Activities like kneeling, squatting, climbing, and heavy lifting will undoubtedly be more difficult and uncomfortable for patients with knee OA, and are considered to play a role in the development of disease.7
It might be expected therefore that sickness absence and job loss from knee OA would be material and greater in those in manual employment than in those whose work is sedentary.
In fact, the matter has been little studied. To inform this part of the review, use was made of a systematic review on OA and work participation by Bieleman et al
This focussed on OA of knee or hip and ‘employment’, ‘sick leave’, ‘work participation’, ‘work changes’, and ‘work adaptations and ‘work transitions’. After screening 1861 abstracts and retrieving 53 full-text articles, 14 reports on OA were finally retained, but of these, only 7 presented data specific to (or preponderantly concerning) the knee. Additionally, a further population study of relevance was identified from a search on work and knee joint surgery described below.
In a nationwide survey of French physicians,9
3,247 patients with knee OA (mean age 66 years) were identified, 17% of whom were still working. In this group, two-thirds reported being limited in their current work capacity and one-fifth reported taking OA-related sick leave.
In a Norwegian population-based study of 3,266 subjects (median age 45 years), 233 cases of knee OA were identified.10
Among these patients, after allowing for age and sex, the odds of being out of work were raised almost 2.5-fold and those of taking >8 weeks of sick leave were almost doubled, relative to others without knee OA.
Woo et al11
reported on 574 patients from Hong Kong with varying degrees of OA or with joint prostheses – 82% of cases relating to the knee, and 60% aged <70 years. In all, 4.7% reported quitting a job because of their OA, 1.4% had workplace adaptations, and 8.7% said that friends or relatives had needed to take leave to care for them. Among those still in paid work (108 subjects) 53% reported taking sick leave in the past 12 months because of their arthritis, at an average of 12.3 lost days per year.
Gupta et al12
conducted an economic evaluation in a population cohort of 1,258 Canadian patients aged ≥55 years (mean 73 years) with disabling hip or knee arthritis (the proportion with knee complaints was not specified): in all, 2.5% reported not working due to OA, and it was estimated that time lost from employment by participants and their unpaid caregivers accounted for 80% of annual OA-related costs, there being several sources of indirect cost (formal lost work time, lost labour productivity, caregiver time losses etc).
Similar findings were reported by Leardini et al13
among 254 patients with OA knee from Italian rheumatology institutes (mean age 66 years), 21% still in work. In this study, 2.4% reported discontinuing work because of their knee OA and 2% had changed the type of work they did in the past 12 months. Some 22% of patients had had OA knee-related sick leave over the period (the denominator for this calculation is assumed to be all patients in work).
Sayre et al14
investigated “employment reduction” due to OA in 2,134 adults with OA (mean age 62 years) registered on a medical service plan database in British Columbia. Among 453 subjects with knee OA, 36% had quit work entirely and 13% had reduced their working hours because of their arthritis.
In the mini-Finland study,15
a survey representative of the Finnish population aged 30-64 years, 4% of subjects had physician-diagnosed knee OA and over 70% of these reported a reduced capacity for work.
Finally, the Dutch CHECK (Cohort Hip and Knee) Study is following an inception cohort of subjects aged 45-65 years with pain and stiffness of the knee and/or hip, recruited in 2005. At baseline,16
51% reported having a paid job for >8 hours/week. At younger ages, work participation rates were similar to those in the general Dutch population, but in 60-64 year olds they were 30-40% lower (those with higher education being relatively protected). In the previous 12 months, 12% of subjects had been on sick leave because of their knee or hip symptoms, a fifth for >3 months. Among those working >8 hours/week, 14% had received adaptations from their workplace to help them (including reduction in working hours (38% of those in receipt of help), workplace aids and changes (25%), and modified duties (10%)); a further 30% would liked to have had such help. Perhaps as expected, those in paid work reported significantly less pain and stiffness and better function (WOMAC scale) and had better SF-36 physical function scores.
Beyond this, the reports identified by Bieleman et al8
offer data on job disruptions, absenteeism, reduced working hours, job change and job dissatisfaction; but only in patients with arthritis as whole or hip OA, and with no exploration by type of work duties. The evidence base on OA knee and work participation is thus small relative to the significance of the problem in ageing western workforces. This gap in evidence, at first sight surprising, probably arises because the main effects of OA have hitherto been seen after retirement. However, the changing demography in workplaces makes further research in this area both timely and important.
Interventions to promote work participation
An important neglected area of investigation concerns effective interventions to improve work participation and comfort in patients with knee OA. Recently, the author undertook a systematic review of workplace and community-based interventions to reduce sickness absence and job loss from musculoskeletal causes;17
although 42 interventional studies were identified in all, including 34 randomised controlled trials (RCTs), none was specific to osteoarthritis.
Observational studies are similarly scant. However, a cross-sectional study by Chen et al18
encouragingly reported that symptomatic knee OA was significantly less common in workplaces which had supportive employment policies (those allowing job switching, and paid sick leave or disability benefits). Longitudinal research is needed to confirm that the apparent benefit did not arise from selection out of work of affected cases; but the study illustrates the scope for research to inform this important area of employment policy.
The review of interventions cited above17
did not include drug or secondary care treatments. To explore this aspect, a search (Search 1) was undertaken in Medline and Embase (to January 2012), combining terms for “treatment” and knee OA with those for work participation, sick leave, sickness absence, employment and work ability. Although 98 abstracts were screened, only two pertinent reports were found, of which only one claimed a useful benefit.19
In this unblinded RCT, patients with rheumatic diseases, including 258 with peripheral arthritis (not specific to the knee), were randomised either to care as usual or to a stepped rheumatological intervention which began with diagnosis, pharmacological treatment of pain and depression, joint injections if needed, reassurance, and education in self management (with encouragement to remain active and advice on ergonomics and on exercise); in those who failed to improve, this was followed by formal rehabilitation and specialist referral. The relative rate of return to work in the intervention group was 1.58 (95%CI 1.14-2.19) and the total annual number of “temporary work disability” days (certificated for sick pay) per 1000 patients was reduced by 26%.
There is a pressing need to expand this very slim evidence base, and to identify effective medical and vocational measures that enhance work participation in patients with large joint OA. In particular, it should be emphasised that extent of work participation is likely to be limited in practice not only by biological factors, such as severity and functional impact of disease, but also by the nature of a patient’s work and the scope to adapt their job role to match their residual capabilities and limitations. Research to demonstrate the feasibility, effectiveness, and cost-effectiveness of workplaces interventions to boost work participation would be particularly valuable, but is presently lacking.