Knee coactivaton and trunk flexion strategies during sit to stand movement performed by individuals with mild and moderate knee osteoarthritis

Abstract

Purpose: Individuals with advanced knee osteoarthritis (KOA) seems to perform the sit to stand (STS) task with higher trunk flexion and higher hamstring:quadriceps coactivation. These movement strategies are adopted as an attempt to spare the load above the affected limb and has been considered a way to overcome quadriceps dysfunction, pain and a possible muscle atrophy of knee extensor muscles in individuals with advanced KOA. Identifying whether individuals with mild and moderate KOA differentiate one each other regarding to these movement strategies would contribute to the panning of interventions involving conservative treatment and training of STS tasks. Thus, the objective of this study was to identify muscle coactivation and trunk flexion in the STS task performed by patients with mild KOA, moderate KOA, and healthy adults. It was hypothesized that patients with mild and moderate KOA would differentiate one each other and also from controls due to greater levels of affected limb hamstring:quadriceps coactivation and higher trunk flexion amplitude during the STS transition. Methods: This was a cross-sectional study. Participated 49 subjects clinically and radiographically diagnosed with KOA according to American College of Rheumatology criteria. Radiographs were scored according to the Kellgren and Lawrence grading system and only subjects classified as mild (KLII) or moderate KOA (KLIII) were included. Three-dimensional analysis of the STS task was performed using a 6-cameras motion capture system (120 Hz; Oqus 300, Qualisys Medical AB, Gothenburg, Sweden) and a synchronized electromiographer (Trigno™ Wireless System (Delsys Inc., Boston, USA) recordered the Myoelectric activity from the vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF), biceps femoris (BF), medial gastrocnemius (MG), and lateral gastrocnemius (LG) at 1200Hz. The amplitude of myoelectric activity was normalized by the amplitude of the myoelectric activity obtained during the maximal voluntary isometric contraction. The participants were asked to rise from the chair at their self-selected pace and were instructed not to use their arms to help them rise from the chair. Three successful STS trials were executed. The following ratio was measured: EXT(VM,VL,RF):FLX(BF,MG,LG). The maximum coactivation ratio was represented as zero; while minimum co-activation is indicated as 1 or -1 (co-activation ratio is positive when agonist is higher than antagonist and vice versa). For intergroup analysis, an ANCOVA with body mass as covariate was performed followed by Bonferroni´s post hoc test for parametric variable and Kruskal Wallis test followed by U Mann- Whitney for non-parametric variables. (α ≤ 0.05). Results: A total of 13 subjects were diagnosed as moderate KOA and were included in the group GOAIII (5 females and 8 males, age: 58 ± 5.34 years, height : 1.67 ± 0.09, mass: 84.81 ± 13.24 and BMI: 30.83 ± 3.43); There was 17 volunteers diagnosed as mild KOA (10 females and 7 males, age: 56.04± 5.34 years, height;: 1.67 ±0.08, mass: 74.43± 8.76 and BMI: 26.75 ±3.09) and composed the groups called as GOAII. Nineteen volunteers composed the control group (GC) (9 females and 10 males, age 55.40± 6.33 years, height: 1.66± 0.09; mass: 71.67± 13.27 and BMI: 25.98± 3.61). Age and height presented homogeneity between groups. The moderate group had body mass and body mass index (BMI) higher than the control group (P = 0.001; P < 0.001, respectively) and mild group (P = 0.007; P = 0.002, respectively). For hamstring:quadriceps coactivation ratio, the intergroup comparison revealed significant differences among controls, mild and moderate KOA (p≤0.05) and though the intergroup comparisons was observed that only patients with mild KOA performed the task with higher levels of hamstring: quadriceps than controls than controls. For the trunk flexion during the STS transition there was statistically significant differences across the groups ( [F (2, 49) = 4,792], p =0,013; partial η2 = 0,176) when adjusted for body mass and follow up Bonferroni´s post hoc test revealed that only patients with moderate KOA performed the STS task with higher trunk flexion than controls. Conclusions: Although in the present study mild and moderate KOA did not differentiate one each other regarding of the proposed variables, the groups presented movement strategies that differentiate each of them from controls. While those with mild KOA performed the STS task with higher hamstring:quadriceps coactivation ratio, those with moderate KOA got up from the chair with higher trunk flexion than controls. This finding gave an insight about the different movement adaptations for STS transition required for patients with mild and moderate KOA, which are differently performed and should be taken into account in interventions involving the task retraining.