Risk factors for functional decline in osteoarthritis of the hip or knee

Purpose of review To summarize recent studies on risk factors for functional decline (i.e. worsening of pain and activity limitations) in osteoarthritis of the hip or knee; after a long period of neglect, information on risk factors for functional decline has markedly improved in recent years. Recent findings Studies show slow worsening of pain and activity limitations over time. There is a considerable between-individual variation in the course of pain and activity limitations; identification of risk factors for functional decline is therefore highly relevant. Risk factors for functional decline include characteristic physical impairments in osteoarthritis (pain, stiffness, reduced muscle strength, laxity of the knee joint, proprioceptive inaccuracy, poor standing balance and impaired range of joint motion), cognitive and visual impairments, comorbidity and overweight, psychological and social factors (anxiety, depression, fatigue, poor self-efficacy and social support), health behaviors and sociodemographic factors. Summary The information on risk factors can be used pragmatically to construct prediction rules on functional decline in osteoarthritis patients. Both clinicians and patients value the ability to prognosticate future pain and activity limitations. Furthermore, the information on risk factors can be used to construct causative models to explain pain and activity limitations: examples include 'instability of joints' and 'avoidance of activity' as causal mechanism of pain and activity limitations. Improved understanding of pain and activity limitations is the basis for improved treatment and rehabilitation of osteoarthritis patients.