Background: chronic knee pain is still considered a fairly benign disease by many, an 'unavoidable' consequence of ageing. This passive acceptance may be unnecessarily exposing older people to disability and serious co-morbidity. The aim of this study was to determine the disease burden associated with chronic knee pain and the role of knee extensor strength as a modifiable risk factor.
Methods: a longitudinal cohort study with 2-year follow-up conducted among 1,587 community-dwelling men aged 70 years and over, 637 (40%) reported chronic knee pain. Of the 950 (60%) men without knee pain at baseline, 768 (81%) returned for the follow-up assessment with 150 (20%) reporting incident chronic knee pain.
Results: knee pain was significantly associated with marked mobility disability [odds ratio (OR) 2.38; 95% confidence interval (CI) 1.74-3.29], falls (OR: 1.31; 95% CI: 1.01-1.70) and having four or more co-morbidity (OR: 1.63; 95% CI: 1.16-2.30) as well as reduced knee extensor strength and mass (dual X-ray absorptiometry). Men with incident knee pain at the 2-year follow-up assessment demonstrated greater increases in these measures of disease burden and greater decreases in muscle strength and mass, compared with those without incident chronic knee pain. Obesity, high co-morbidity burden, back pain, higher levels of physical activity or low knee extensor strength were all significant risk factors for incident knee pain.
Conclusion: prevention of chronic knee pain may reduce a considerable burden of mobility disability and increased risk of serious co-morbidity among older men.
Keywords: disability; knee pain; muscle strength; older people.