Is long-term physical activity safe for older adults with knee pain?: a systematic review

Abstract

Purpose: Knee pain attributable to osteoarthritis (OA) is common in older adults. Although exercise and physical activity are consistently recommended for older adults with knee pain in clinical guidelines, physical activity levels in this population remain low. This may, in part, be due to concerns over its long-term safety. Common and persisting narratives regarding joint “wear and tear” may lead to attributions that physical activity causes further joint damage, whilst pain during activity may be perceived as an indicator of harm. The aim of this study was to synthesise existing literature to determine whether long-term physical activity is safe for older adults with knee pain. Methods: A comprehensive systematic review was conducted using multiple electronic databases including MEDLINE, EMBASE, CINAHL, CENTRAL, AMED, SPORTDiscus, CISDOC, NIOSHTIC-2 and HSELINE from inception until 16th May 2013. Two reviewers independently screened all titles, abstracts and full texts for study inclusion and exclusion criteria. Any initial disagreement was resolved by discussion or consensus with a third reviewer where necessary. Inclusion criteria were: a) randomised controlled trials (RCT), prospective cohort studies (PCS) or case control studies (CCS); b) including adults over 45 years old with knee pain or OA; c) undertaking exercise or physical activity explicitly over at least three months; and d) measuring a safety related outcome including adverse events, pain, physical functioning, radiographic or magnetic resonance imaging (MRI) OA biomarker progression or progression to total knee replacement (TKR). Included studies were assessed for risk of bias using the Cochrane risk of bias tool for RCT and the Quality In Prognosis Studies risk of bias tool for PCS and CCS. Safety data were extracted and analysed by narrative synthesis. Results: In total, 8605 unique references were identified by the search and 37 primary studies were included in the review. The included studies were made up of 35 RCT, 1 PCS and 1 CCS, which were undertaken in 16 different countries and were of variable quality. In total, 7194 older adults with either knee pain or clinical, radiographic and combined OA diagnoses were included. The 35 RCT investigated a variety of exercise and physical activity interventions including: walking, Tai Chi, aerobics, strengthening, flexibility, balance, and exercise in water, of between three months and two years duration. 15 studies provided data on adverse events, 35 on pain, 32 physical functioning and 5 some form of radiographic or MRI biomarker of OA progression. In terms of safety results, only eight serious adverse events were reported: one inguinal hernia, five falls (one of which resulted in a head laceration injury and one a fractured radius), one participant fractured her foot as a result of dropping a weight and one had an exacerbation of existing back pain. Mild adverse events of increase in knee pain occurred in a minority of individuals in eight RCT. There was no evidence of a statistically significant increase in pain, decrease in physical function, or deterioration in radiographic or MRI findings (compared to either control group at follow up or within the same group comparing baseline to post treatment data). The single, moderate risk of bias, CCS investigated factors associated with OA progression to TKR in Finnish older adults. It concluded that increasing levels of regular exercise were associated with less chance of progression when compared to those who did not carry out regular exercise. The single, high risk of bias, PCS investigated occupational physical activity exposure in older adult members of a French energy company. From a set of 10 physical activity variables, only prolonged exposure to kneeling and squatting activities (between 1 and 25 years) was associated with severe knee pain (Adjusted OR 1.4 95% CI 1.04, 1.85). Overall risk of bias across studies was variable with performance, attrition, and reporting bias frequently being unclear. Conclusions: This systematic review demonstrates that long-term exercise and physical activity, lasting three months or more, is safe for older adults with existing knee pain or OA. Serious adverse events with exercise are very rare. However, the risk of bias of included studies was often a concern. These findings match existing expert consensus regarding the safety of exercise and current recommendations for exercise and physical activity as “core” treatments in clinical guidelines.