Knee pain, knee osteoarthritis, and the risk of fracture

OBJECTIVE: Patients with osteoarthritis (OA) have increased bone mineral density; however, the association between knee OA and fracture is controversial. Few data exist on the association between knee pain and fracture. We examined the association of knee OA and knee pain with fracture and falls in elderly men and women. METHODS: The study group comprised 6,641 men and women ages > or =75 years who participated in a 3-year randomized controlled trial of intramuscular vitamin D therapy. Patients completed a questionnaire about knee pain and OA. Fracture and fall data were collected prospectively every 6 months. RESULTS: Knee pain prevalence and a clinician diagnosis of knee OA were 35.2% and 6.8%, respectively. A total of 436 incident nonvertebral fractures were reported, and 3,992 patients sustained a fall. Prevalent knee pain was associated with an increased risk of falls (hazard ratio HR 1.26, 95% confidence interval 95% CI 1.17-1.36) and hip fracture (HR 2.0, 95% CI 1.18-3.37). Increasing severity of knee pain was associated with a greater risk of falls and hip fracture. Clinician diagnosis of knee OA was associated with an increased risk of nonvertebral fractures (HR 1.61, 95% CI 1.09-2.36). The increased risk of fracture was not substantially reduced by adjusting for falls, but was attenuated by adjustment for the use of walking aids. CONCLUSION: Patients with a clinical diagnosis of knee OA and with knee pain have an increased risk of nonvertebral and hip fracture. This is not explained by the increased risk of falls, but is more likely to be due to the severity of falls sustained. Knee pain and OA should be regarded as independent risk factors for fracture.