B. Metcalf

Lateral wedge insoles for medial knee osteoarthritis: Effects on lower limb frontal plane biomechanics

BACKGROUND Lateral wedges reduce the peak knee adduction moment and are advocated for knee osteoarthritis. However some patients demonstrate adverse biomechanical effects with treatment. Clinical management is hampered by lack of knowledge about their mechanism of effect. We evaluated effects of lateral wedges on frontal plane biomechanics, in order to elucidate mechanisms of effect. METHODS Seventy three participants with knee osteoarthritis underwent gait analysis with and without 5° lateral wedges. Frontal plane parameters at the foot, knee and hip were evaluated, including peak knee adduction moment, knee adduction angular impulse, center of pressure displacement, ground reaction force, and knee-ground reaction force lever arm. FINDINGS Lateral wedges reduced peak knee adduction moment and knee adduction angular impulse (-5.8% and -6.3% respectively, both P<0.001). Although reductions in peak moment were correlated with more lateral center of pressure (r=0.25, P<0.05), less varus malalignment (r values 0.25-0.38, P<0.05), reduced knee-ground reaction force lever arm (r=0.69, P<0.01), less hip adduction (r=0.24, P<0.05) and a more vertical frontal plane ground reaction force vector (r=0.67, P<0.001), only reduction in knee-ground reaction force lever arm was significantly predictive in regression analyses (B=0.056, adjusted R(2)=0.461, P<0.001). INTERPRETATION Lateral wedges significantly reduce peak knee adduction moment and knee adduction angular impulse. It seems a reduced knee-ground reaction force lever arm with lateral wedges is the central mechanism explaining their load-reducing effects. In order to understand why some patients do not respond to treatment, future evaluation of patient characteristics that mediate wedge effects on this lever arm is required.

Gluteal tendinopathy and hip osteoarthritis: different pathologies, different hip biomechanics

BACKGROUND Gluteal tendinopathy (GT) and hip osteoarthritis (OA) are the most common causes of hip pain and associated disability in older adults. Pain and altered walking biomechanics are common to both conditions. This study aimed to compare three-dimensional walking biomechanics between individuals with unilateral, symptomatic GT and HOA. METHODS Sixty individuals with symptomatic unilateral GT confirmed by magnetic-resonance-imaging and 73 individuals with symptomatic unilateral HOA (Kellgren-Lawrence Grade ≥ 2) underwent three-dimensional gait analysis. Maximum and minimum values of the external sagittal hip moment, the first peak, second peak and mid-stance minimum of the hip adduction moment (HAM), sagittal plane hip excursion and hip joint angles, pelvic obliquity and trunk lean, at the three HAM time points during stance phase of walking were compared between groups. RESULTS Compared to individuals with HOA, those with GT exhibited a greater hip peak extension moment (P < 0.001) and greater HAM throughout the stance phase of walking (P = 0.01-P < 0.001), greater hip adduction (P < 0.001) and internal rotation (P < 0.01-P < 0.001) angles and lower hip flexion angles and excursion (P = 0.02 - P < 0.001). Individuals with HOA exhibited a greater forward trunk lean (P ≤ 0.001) throughout stance, and greater ipsilateral trunk lean in the frontal plane (P < 0.001) than those with GT. CONCLUSION Despite presence of pain in both conditions, hip kinematics and kinetics differ between individuals with symptomatic unilateral GT and those with symptomatic unilateral HOA. These condition-specific impairments may be targets for optimization of management of HOA and GT.

Psychological Factors and Pain Exacerbation in Knee Osteoarthritis: A Web Based Case-Crossover Study

Objectives: The pain experienced by osteoarthritis (OA) patients is neither constant nor unchanging and patients experience episodes of pain exacerbations. Using an innovative web based case-crossover design, we evaluated whether psychological factors are risk factors for pain exacerbations in patients with knee OA. Methods: In a 3-months internet-based case-crossover study, participants with symptomatic knee OA were recruited and followed at 10-day intervals (control periods). Participants were also instructed to log on to the study website if they experienced a knee pain exacerbation (case periods). Pain exacerbation was defined as an increase of ≥ 2 on a participant’s numerical rating scale (0-10) from his/her usual background pain score reported at baseline visit. The periods were 10 days for affect measures and 30 days for pain coping/perceived stress measures. The relation of psychological factors to the risk of pain exacerbation was examined using conditional logistic regression. Results: Of 298 participants recruited, 149 and 54 provided both case and control periods with no overlap for examining affect and pain coping/perceived stress factors respectively. Higher negative affect (negative affect score ≥ 18: odds ratio (OR) 6.49; 95% CI 3.45-12.2) and passive coping strategies (OR 1.26; 95% CI 1.05-1.50) were associated with increased risk of pain exacerbations; while higher active coping strategies (OR 0.81; 95% CI 0.66-0.98) had a protective effect. Conclusion: The findings emphasize the need for avoidance of negative affect and passive pain coping strategies and conversely reinforce the benefit of active pain coping strategies in prevention and management of OA pain exacerbations.