High-intensity versus low-intensity resistance training in patients with knee osteoarthritis: A randomized controlled trial.

OBJECTIVES: To assess whether (i) high-intensity resistance training (RT) leads to increased muscle strength compared to low-intensity RT in patients with knee osteoarthritis (OA); and (ii) RT with vitamin D supplementation leads to increased muscle strength compared to placebo in a subgroup with vitamin D deficiency. DESIGN: Randomized controlled trial. SETTING: Outpatient rehabilitation centre. SUBJECTS: Patients with knee OA. INTERVENTIONS: 12 weeks of RT at high-intensity RT (70-80% of 1-repetition maximum (1-RM)) or low-intensity RT (40-50% of 1-RM) and 24 weeks of vitamin D (1200 International units vitamin D3 per day) or placebo supplementation. MAIN MEASURES: Primary outcome measure was isokinetic muscle strength. Other outcome measure for muscle strength was the estimated 1-RM. Secondary outcome measures were knee pain and physical functioning. RESULTS: 177 participants with a mean age of 67.6 ± 5.8 years were included, of whom 50 had vitamin D deficiency. Isokinetic muscle strength (in Newton metre per kilogram bodyweight) at start, end and 24 weeks after the RT was 0.98 ± 0.40, 1.11 ± 0.40, 1.09 ± 0.42 in the high-intensity group and 1.02 ± 0.41, 1.15 ± 0.42, 1.12 ± 0.40 in the low-intensity group, respectively. No differences were found between the groups, except for the estimated 1-RM in favour of the high-intensity group. In the subgroup with vitamin D deficiency, no difference on isokinetic muscle strength was found between the vitamin D and placebo group. CONCLUSIONS: High-intensity RT did not result in greater improvements in isokinetic muscle strength, pain and physical functioning compared to low-intensity RT in knee OA, but was well tolerated. Therefore these results suggest that either intensity of resistance training could be utilised in exercise programmes for patients with knee osteoarthritis. No synergistic effect of vitamin D supplementation and RT was found, but this finding was based on underpowered data.

Factors associated with upper leg muscle strength in knee osteoarthritis: A scoping review.

OBJECTIVE: Muscle weakness is common and strongly related to clinical outcome in patients with knee or hip osteoarthritis. To date, there is no clear overview of the information on factors associated with muscle strength in knee and hip osteoarthritis. The aim of this paper is to provide an overview of current knowledge on factors associated with upper leg muscle strength in this population. DESIGN: The framework of a scoping review was chosen. MEDLINE database was searched systematically up to 22 April 2017. Studies that described a relationship between a factor and muscle strength in knee or hip osteoarthritis were included. RESULTS: A total of 65 studies met the inclusion criteria. In studies of knee osteoarthritis, 4 factors were consistently found to be associated with lower muscle strength. Due to the low number of studies on hip osteoarthritis no conclusions could be drawn on associations. CONCLUSION: Lower muscle quality, physical inactivity, more severe joint degeneration, and higher pain are reported to be associated with lower strength in the upper leg muscles in knee osteoarthritis. Future research into knee osteoarthritis should focus on other potential determinants of muscle strength, such as muscle quantity, muscle activation, nutrition and vitamins, and inflammation. In hip osteoarthritis, more research is needed into all potential determinants.

Falls Associated with Muscle Strength in Patients with Knee Osteoarthritis and Self-reported Knee Instability.

OBJECTIVE: We aimed to evaluate the associations between knee muscle strength (MS) and falls, controlling for knee joint proprioception, varus-valgus knee joint laxity, and knee pain, among patients with knee osteoarthritis (OA) reporting knee instability. METHODS: A sample of 301 subjects (203 women, 98 men, 35-82 yrs) with established knee OA and self-reported knee instability was studied. The occurrence of at least 1 fall in the previous 3 months was assessed by questionnaire. Maximum knee extension and flexion strength were measured isokinetically. Additionally, proprioception, varus-valgus laxity, and pain were assessed. Student t tests were used to assess differences between subgroups. The association of muscle strength and falls was calculated using univariate and multivariate logistic regression analysis. RESULTS: Over 10% of the subjects (31 out of 301) reported a fall in the previous 3 months. High knee extension muscle strength (crude OR 0.3, 95% CI 0.1-0.8, p = 0.022) and high knee flexion muscle strength (crude OR 0.2, 95% CI 0.0-1.0, p = 0.048) were associated with a lower risk of falls. Proprioception and laxity did not confound this relationship. After adjusting for pain, extensor strength had an adjusted OR of 0.5 (95% CI 0.2-1.4, p = 0.212) for falls and flexor strength had an adjusted OR of 0.4 (95% CI 0.1-2.3, p = 0.312). CONCLUSION: High knee extension and flexion muscle strength decreased the risk of falls in patients with knee OA and self-reported knee instability. After considering the effect of pain, there was insufficient statistical power to detect an association between muscle strength and falls, which might be because of the low number of subjects who fell (n = 31).