knee osteoarthritis

Influence of Experimental Knee Pain on Bilateral Loading Patterns during Walking in Healthy Individuals

Purpose: Knee pain is a chief symptom of knee pathology. Both acute and chronic knee pain result in altered joint loads during walking, which potentially result in mechanical and biological changes in knee articular cartilage. Due to confounding factors in clinical knee pain (effusion, muscle weakness, inflammation, structural changes), it is difficult to examine the independent effect of knee pain on walking mechanics. The purpose of this study is to examine whether unilateral experimentally induced knee pain influences bilateral loading patterns during walking in healthy individuals. Methods: This study was a controlled laboratory, cross-over trial. Each of 30 able-bodied subjects (M = 20, F = 10; 23 ± 2.4 yrs, 71 ± 12.7 kg, 178 ± 8.2 cm) completed three experimental sessions: pain (5.0% NaCl infusion), sham (0.9% NaCl infusion), and control (no infusion) in a counterbalanced order, 2 days apart (a washout period). For the experimental sessions, hypertonic (5% NaCl) or isotonic (0.9% NaCl) saline was continuously infused into the right (involved limb) infrapatellar fat pad using a portable infusion pump, which produced a continuous saline flow of 0.154mL/min (total 2.16 mL) for 14 min for the pain or sham session, respectively. No infusion was administered to the control session. Subjects and investigators were blinded regarding the saline solution which was being infused. During each of three experimental sessions, subjects performed 30-sec gait trials at a self-selected speed at two time points (pre- and post-infusion). Ground reaction force (GRF) data were collected using an AMTI instrumented force-sensing tandem treadmill (1200 Hz). The first 4 successful gait cycles in each limb were used for data analysis. A functional data analysis approach (α = .05) was used to detect time (pre- and post-infusion) x limb (involved vs. uninvolved) interactions for the vertical, anterior-posterior, and medial-lateral GRF. Results: Significant time x limb interactions were observed during the pain session (hypertonic saline; 5.0% NaCl; p < .05). Experimental knee pain resulted in up to (i) 0.05 N/kg less vertical GRF and 0.02 N/kg more vertical GRF during various stance phases, (ii) 0.01 N/kg less breaking GRF during loading response, and (iii) 0.007 N/kg less lateral GRF and 0.007 N/kg more lateral GRF during various stance phases in the involved limb. Conclusions: Relative to the pre-infusion condition, subjects during the knee pain condition tended to walk with less vertical, posterior and lateral GRF in the involved limb (painful limb) across various portions of stance, which simultaneously increased loads in the uninvolved limb (non-painful limb). Our data suggest that compensatory loading patterns occur simultaneously for the involved and uninvolved limbs. This unloading pattern in the involved limb may be due to perception of knee pain, which can make subjects feel fear for damaging or provoking pain more during walking. Moreover, voluntary and/or involuntary quadriceps inhibition (e.g., neuromuscular activation and strength) due to experimentally induced knee pain may play a role in reducing the loads in the involved limb because the quadriceps support the center of body mass eccentrically from initial loading response to midstance to prevent collapse of the lower limbs. These asymmetrical loading patterns due to knee pain and associated with neural inhibition may be a risk factor for knee joint disease progression via changes in mechanical components.
Listed In: Biomechanics, Gait

Quantifying varus and valgus thrust in individuals with severe knee osteoarthritis

Background: Gait abnormalities can influence surgical outcomes in people with severe knee osteoarthritis (OA) and thus a thorough understanding of gait abnormalities in these people prior to arthroplasty is important. Varus-valgus thrust is a characteristic linked to OA disease progression that has not yet been investigated in a cohort with severe knee OA awaiting knee arthroplasty. The aims of this study were to determine i) prevalence of varus and valgus thrust in a cohort with severe knee OA compared to an asymptomatic group, ii) whether the thrust magnitude differed between these groups iii) differences between varus and valgus thrusters within the OA cohort and iv) whether certain measures could predict thrust in the OA cohort. Methods: 40 patients with severe knee OA scheduled for primary TKR and 40 asymptomatic participants were recruited. Three-dimensional gait analysis was performed on all participants, with the primary biomechanical measures of interest being: varus and valgus thrust, knee adduction angle, peak KAM, and KAM impulse. Additionally, static knee alignment and quadriceps strength were assessed in the subgroup with knee OA. Findings: No difference was found in the prevalence of varus and valgus thrust between the severe OA and control groups (Pearson chi-square = 3.735, p value = 0.151). The OA varus thrust group had a significantly higher peak KAM (p=0.000), KAM impulse (p=0.001), static alignment (p=0.021), and lower quadriceps strength (p=0.041) than the valgus thrust group. Peak KAM and quadriceps strength were found to explain 34.9% of the variation in maximum thrust, such that an increase in KAM and a decrease in quadriceps strength were associated with an increase in maximum (varus) thrust. Interpretation: Few differences between the severe OA and control groups were seen, however dichotomizing the groups into varus and valgus cohorts revealed a number of biomechanical differences. Patients with severe OA are often treated as a homogenous cohort; however, by classifying which individuals have a varus or valgus thrust, we have identified a subset of patients with poorer biomechanics who could potentially be at a higher risk of a worse outcome after surgery.
Listed In: Biomechanics, Gait, Orthopedic Research