Course and predictors of upper leg muscle strength over 48 months in subjects with knee osteoarthritis: Data from the osteoarthritis initiative.

Objectives: Weakness of upper leg muscles has a negative impact on future disease and functional status in subjects with knee osteoarthritis (OA). The aims of the present study were to (i) describe the course of muscle strength over 48 months and (ii) identify baseline predictors for a decline in upper leg muscle strength over time in subjects with knee OA. Methods: Data were obtained from the Osteoarthritis Initiative (OAI) database, a multicenter, observational study of knee OA. Upper leg muscle strength (in N/kg) was measured at baseline, 24 and 48 months. Potential baseline predictors included demographics, OA-specific and health and lifestyle related factors. Linear mixed model analyses were performed. Results: A total of 1390 subjects with knee osteoarthritis were included. A statistically significant decline of muscle strength was found between baseline and 24 months (B = -0.186, 95%CI [-0.358,-0.014], p = 0.03), but not between other time points (24-48 months p = 0.89, and baseline and 48 months p = 0.058). Predictors of a decline in muscle strength over time included demographic predictors (older age, being female, higher body mass index (BMI)), one lifestyle predictor (lower dietary protein intake) and one OA-specific predictor (radiographic severity). Conclusions: Muscle strength declined over time in subjects with knee OA. The identified predictors may help clinicians to select and treat subjects with knee OA at risk of a decline in muscle strength.

Dietary protein intake and upper leg muscle strength in subjects with knee osteoarthritis: data from the osteoarthritis initiative.

The aims of this study were (1) to describe dietary protein intake, and (2) to evaluate the association between dietary protein intake and upper leg muscle strength in subjects with knee osteoarthritis (OA). Baseline data from the OA was used, in a cross-sectional study. All subjects were diagnosed with symptomatic and radiographic knee OA. Daily dietary protein intake was measured with the Block Brief 2000 food frequency questionnaire (g/kg body weight). The sum of knee flexion and extension strength of the index knee (N/kg bodyweight) was assessed with the Good Strength chair test. Linear regression analysis was used to test the association between dietary protein intake and muscle strength, adjusting for relevant confounders. Data from 1316 subjects (mean age 61.4 ± SD 9.1 years, 57.0% female) were used. The mean daily protein intake was 0.72 ± SD 0.30 g/kg bodyweight, and 65.1% of the subjects had a protein intake lower than the recommended daily allowance of 0.8 g/kg bodyweight. The mean muscle strength was 5.4 ± SD 2.1 N/kg bodyweight. Lower protein intake was significantly associated with lower muscle strength (B = 0.583, 95% CI 0.230-0.936, p = 0.001). The majority of the subjects with knee OA had a dietary protein intake lower than the recommended daily allowance. Lower protein intake was associated with lower upper leg muscle strength. Longitudinal observational and interventional studies are needed to establish whether dietary protein intake has a causal effect on muscle strength in subjects with knee OA.

Concentration and size distribution of particles in abstracted groundwater.

Particle number concentrations have been counted and particle size distributions calculated in groundwater derived by abstraction wells. Both concentration and size distribution are governed by the discharge rate: the higher this rate the higher the concentration and the higher the proportion of larger particles. However, the particle concentration in groundwater derived from abstraction wells, with high groundwater flow velocities, is much lower than in groundwater from monitor wells, with minimal flow velocities. This inconsistency points to exhaustion of the particle supply in the aquifer around wells due to groundwater abstraction for many years. The particle size distribution can be described with the help of a power law or Pareto distribution. Comparing the measured particle size distribution with the Pareto distribution shows that particles with a diameter >7 microm are under-represented. As the particle size distribution is dependent on the flow velocity, so is the value of the "Pareto" slope beta.