Patients with OA have increased fall risk, which can lead to reduced mobility and curtailment of daily activities. Patients with OA also show varied and altered mobility in a sit-to-stand test, suggesting that both poor lower limb strength and flexibility need to be addressed with targeted interventions in this population. Altered mobility is also associated with pain in patients with OA. The cause of decreased mobility and increased pain is often a result of body weight. In a 5-year follow-up study, classes of knee OA were identified as being associated with good, moderate or poor outcomes; characteristics of the poor outcomes class included high BMI, worse pain, >2 co-morbidities and avoidance of activities. Avoidance of activities is a particularly important outcome since this could lead to a downward spiral of decreased physical functioning, falls and further avoidance of activities.