Effects of Running and Walking on Osteoarthritis and Hip Replacement Risk :

Preventive strategies against knee osteoarthritis (OA) require a knowledge of risk factors that influence the initiation of the disorder and its subsequent progression. This population-based longitudinal study was performed to address this issue. Ninety-nine men and 255 women aged > or =55 years had baseline interviews and weight-bearing knee radiographs in 1990-1991. Repeat radiographs were obtained in 1995-1996 (mean followup duration 5.1 years, median age at followup 75.8 years). Risk factors assessed at baseline were tested for their association with incident and progressive radiographic knee OA by logistic regression. Rates of incidence and progression were 2.5% and 3.6% per year, respectively. After adjusting for age and sex, the risk of incident radiographic knee OA was significantly increased among subjects with higher baseline body mass index (odds ratio [OR] 18.3, 95% confidence interval [95% CI] 5.1-65.1, highest versus lowest third), previous knee injury (OR 4.8, 95% CI 1.0-24.1), and a history of regular sports participation (OR 3.2, 95% CI 1.1-9.1). Knee pain at baseline (OR 2.4, 95% CI 0.7-8.0) and Heberden's nodes (OR 2.0, 95% CI 0.7-5.7) were weakly associated with progression. Analyses based on individual radiographic features (osteophyte formation and joint space narrowing) supported differences in risk factors for either feature. Most currently recognized risk factors for prevalent knee OA (obesity, knee injury, and physical activity) influence incidence more than radiographic progression. Furthermore, these factors might selectively influence osteophyte formation more than joint space narrowing. These findings are consistent with knee OA being initiated by joint injury, but with progression being a consequence of impaired intrinsic repair capacity.

To evaluate the effects of moderate exercise on glycosaminoglycan (GAG) content in knee cartilage in subjects at high risk of knee osteoarthritis (OA). Forty-five subjects (16 women, mean age 46 years, mean body mass index 26.6 kg/m(2)) who underwent partial medial meniscus resection 3-5 years previously were randomized to undergo a regimen of supervised exercise 3 times weekly for 4 months or to a nonintervention control group. Cartilage GAG content, an important aspect of the biomechanical properties of cartilage, was estimated by delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC), with results expressed as the change in the T1 relaxation time in the presence of Gd-DTPA (T1[Gd]). Thirty of 45 patients were examined by dGEMRIC at baseline and followup. The exercise group (n = 16) showed an improvement in the T1(Gd) compared with the control group (n = 14) (15 msec versus -15 msec; P = 0.036). To study the dose response, change in the T1(Gd) was assessed for correlation with self-reported change in physical activity level, and a strong correlation was found in the exercise group (n = 16, r(S) = 0.70, 95% confidence interval [95% CI] 0.31-0.89) and in the pooled group of all subjects (n = 30, r(S) = 0.74, 95% CI 0.52-0.87). This in vivo cartilage monitoring study in patients at risk of knee OA who begin exercising indicates that adult human articular cartilage has a potential to adapt to loading change. Moderate exercise may be a good treatment not only to improve joint symptoms and function, but also to improve the knee cartilage GAG content in patients at high risk of developing OA.

Knee osteoarthritis (OA) is highly prevalent, especially in the elderly. Preventive strategies require a knowledge of risk factors that precede disease onset. The present study was conducted to determine the longitudinal risk factors for knee OA in an elderly population.