Knee Muscle Activation Patterns Research Articles

Neuromechanical assessment of knee joint instability during perturbed gait in patients with knee osteoarthritis

Knee joint instability is frequently reported by patients with knee osteoarthritis (KOA). Objective metrics to assess knee joint instability are lacking, making it difficult to target therapies aiming to improve stability. Therefore, the aim of this study was to compare responses in neuromechanics to perturbations during gait in patients with self-reported knee joint instability (KOA-I) versus patients reporting stable knees (KOA-S) and healthy control subjects.Forty patients (20 KOA-I and 20 KOA-S) and 20 healthy controls were measured during perturbed treadmill walking. Knee joint angles and muscle activation patterns were compared using statistical parametric mapping and discrete gait parameters. Furthermore, subgroups (moderate versus severe KOA) based on Kellgren and Lawrence classification were evaluated.Patients with KOA-I generally had greater knee flexion angles compared to controls during terminal stance and during swing of perturbed gait. In response to deceleration perturbations the patients with moderate KOA-I increased their knee flexion angles during terminal stance and pre-swing. Knee muscle activation patterns were overall similar between the groups. In response to sway medial perturbations the patients with severe KOA-I increased the co-contraction of the quadriceps versus hamstrings muscles during terminal stance.Patients with KOA-I respond to different gait perturbations by increasing knee flexion angles, co-contraction of muscles or both during terminal stance. These alterations in neuromechanics could assist in the assessment of knee joint instability in patients, to provide treatment options accordingly. Furthermore, longitudinal studies are needed to investigate the consequences of altered neuromechanics due to knee joint instability on the development of KOA.

Biofeedback for Gait Retraining Based on Real-Time Estimation of Tibiofemoral Joint Contact Forces.

Biofeedback assisted rehabilitation and intervention technologies have the potential to modify clinically relevant biomechanics. Gait retraining has been used to reduce the knee adduction moment, a surrogate of medial tibiofemoral joint loading often used in knee osteoarthritis research. In this paper, we present an electromyogram-driven neuromusculoskeletal model of the lower-limb to estimate, in real-time, the tibiofemoral joint loads. The model included 34 musculotendon units spanning the hip, knee, and ankle joints. Full-body inverse kinematics, inverse dynamics, and musculotendon kinematics were solved in real-time from motion capture and force plate data to estimate the knee medial tibiofemoral contact force (MTFF). We analyzed five healthy subjects while they were walking on an instrumented treadmill with visual biofeedback of their MTFF. Each subject was asked to modify their gait in order to vary the magnitude of their MTFF. All subjects were able to increase their MTFF, whereas only three subjects could decrease it, and only after receiving verbal suggestions about possible gait modification strategies. Results indicate the important role of knee muscle activation patterns in modulating the MTFF. While this paper focused on the knee, the technology can be extended to examine the musculoskeletal tissue loads at different sites of the human body.

Knee muscle activation patterns are altered in patients with moderate knee osteoarthritis during gait retraining designed to reduce the knee adduction moment

Knee muscle activation patterns are altered in patients with moderate knee osteoarthritis during gait retraining designed to reduce the knee adduction moment

Increased duration of co-contraction of medial knee muscles is associated with greater progression of knee osteoarthritis

BackgroundAs knee osteoarthritis (OA) cannot be cured, treatments that slow structural disease progression are a priority. Knee muscle activation has a potential role in OA pathogenesis. Although enhanced knee muscle co-contraction augments joint stability; this may speed structural disease progression by increased joint load. ObjectiveThis study investigated the relationship between cartilage loss and duration of co-contraction of medial/lateral knee muscles in medial knee OA. DesignProspective cohort study. MethodsMedial (vastus medialis; semimembranosus) and lateral (vastus lateralis; biceps femoris) knee muscle myoelectric activity was recorded in 50 people with medial knee OA during natural speed walking at baseline. Medial tibial cartilage volume was measured from MRI at baseline and 12 months. Relationships between percent volume loss and duration of co-contraction of medial/lateral muscles around stance phase and ratio of duration of medial to lateral muscle co-contraction were evaluated with multiple linear regression. ResultsGreater duration of medial muscle co-contraction and greater duration of medial relative to lateral co-contraction correlated positively with annual percent loss of medial tibial cartilage volume (P = 0.003). Estimated cartilage loss was 0.14 (95% confidence interval −0.23 to −0.05) greater for each increase in medial muscle co-contraction duration of 1% of the gait cycle. Lateral muscle co-contraction inversely correlated with cartilage loss. ConclusionData support the hypothesis that augmented medial knee muscle co-contraction underpins faster progression of medial knee OA. Increased duration of lateral muscle co-contraction protected against medial cartilage loss. Exercise and biomechanical interventions to change knee muscle activation patterns provide possible candidates to slow progression of knee OA.

Fatigue’s Lack of Effect on Thigh-Muscle Activity in Anterior Cruciate Ligament–Reconstructed Patients During a Dynamic-Landing Task

As individuals returning to activity after anterior cruciate ligament reconstruction (ACLr) likely experience fatigue, understanding how fatigue affects knee-muscle activation patterns during sport-like maneuvers is of clinical importance. Fatigue has been suggested to impair neuromuscular control strategies. As a result, fatigue may place ACLr patients at increased risk of developing posttraumatic osteoarthritis (OA). To determine the effects of fatigue on knee-muscle activity post-ACLr. Case control. University laboratory. 12 individuals 7-10 mo post-ACLr (7 male, 5 female; age 22.1 ± 4.7 y; 1.8 ± 0.1 m; mass 77.7 ± 11.9 kg) and 13 controls (4 male, 9 female; age 22.9 ± 4.3 y; 1.7 ± 0.1 m; mass 66.9 ± 9.8 kg). Fatigue was induced via repetitive sets of double-leg squats (n = 8), which were interspersed with sets of single-leg landings (n = 3), until squats were no longer possible. 2 × 2 repeated-measures ANOVA was used to detect the main effects of group (ACLr, control) and fatigue state (prefatigue, postfatigue) on quadriceps:hamstring cocontraction index (Q:H CCI). All subjects demonstrated higher Q:H CCI at prefatigue compared with postfatigue (F(1,23) = 66.949, P ≤ .001). Q:H CCI did not differ between groups (F(1,23) = 0.599, P = .447). The results indicate that regardless of fatigue state, ACLr individuals are capable of restoring muscle-activation patterns similar to those in healthy subjects. As a result, excessive muscle cocontraction, which has been hypothesized as a potential mechanism of posttraumatic OA, may not contribute to joint degeneration after ACLr.

Differences in knee flexion and extension angles of peak torque between men and women

Background and objections: Anterior cruciate ligament (ACL) injuries are reportedly more prevalent in women compared to men. The aim of the study was to investigate possible differences in knee muscle activation patterns between men (M) and women (W). Methods: Thirty six women with a mean age of 22.0 years (± 2.3) and 34 men (22.9 years ± 2.6) were recruited on a voluntary basis to participate in the study. Bilateral concentric (CON) and eccentric (ECC) bilateral isokinetic testing using a Cybex Norm 7000 was conducted at 60 ◦ /s and 180 ◦ /s. The angle of peak torque at each velocity was used for analysis. Results: No statistically significant differences ( p> 0.05) in angle of peak torque between men and women were observed for CON knee extension and CON knee flexion at either 60 ◦ /s or 180 ◦ /s. There were statistically significant differences for both the left and right legs ( p< 0.05) in ECC knee extension angle of peak torque at 60 ◦ /s, with women displaying smaller angles of peak torque (M: 58.0 ◦ & 56.5 ◦ ; W: 52.8 ◦ & 51.1 ◦ ). Significant differences (p<0.05) were also observed for ECC knee flexion at 60 ◦ /s between men and women, with women having larger angles of peak torque (M: 30.4 ◦ & 30.7 ◦ ; W: 38.2 ◦ & 40.2 ◦ ). At 180 ◦ /s, the only statistically significant difference ( p< 0.05) observed was for the right leg's ECC knee flexion, where the angle of peak torque was again larger for women (M: 39.2 ◦ ; W: 47.1 ◦ ). Conclusions: The significantly different angles of peak torque for ECC knee flexion and extension in women compared to men, may negatively impact their ability to effectively protect the knee joint during landing and cutting, thus putting their ACL at a greater risk for injury.

The effect of balance and strength training on muscle activation, strength and standing balance

Introduction: Strength training has, for many years, been used by athletes to improve sports performance. Recently, balance training has become popular to assist in the reduction of knee injuries. However, the underlying neuromuscular changes resulting from these different training modes have not been evaluated in a consistent, comprehensive fashion. This paper aimed to establish the neuromuscular effects from different types of training by investigating how different training affects the knee muscle activation patterns and strength on isometric and isokinetic tests as well as standing balance.

Gender differences in onset timing and activation of the muscles of the dominant knee during stair climbing

An electromyographical analysis (EMG) of knee muscle activation patterns and time delays has rarely been discussed in the literature. The purpose of this study was to compare the activation time and EMG amplitude of the dominant vastus medialis and medial hamstring muscles during stair climbing. Fifteen male and 18 female subjects participated in this study. The subjects were asked to ascend and descend 14 steps, five times. There was a significant time delay difference between genders during stair climbing (F=8.37, p=0.008). The female subjects demonstrated longer time delays while descending the steps. In addition, the female subjects demonstrated significantly lower normalized EMG amplitude during down stair climbing (F=5.77, p=0.025) while the male subjects demonstrated higher normalized EMG amplitude for the vastus medialis muscle while descending the steps. These results suggest that female subjects possess an increased risk factor for knee injuries during down stair climbing due to muscle activation delays with decreased vastus medialis muscle activity.

Neuromotor and Musculoskeletal Responses to Locomotor Training for an Individual With Chronic Motor Complete AIS-B Spinal Cord Injury

Background/objective: To determine the effects of locomotor training (LT)using body weight support(BWS), treadmill, and manual assistance on muscle activation, bone mineral density (BMD), and body composition changes for an individual with motor complete spinal cord injury (AIS B), 1 year after injury.Methods: A man with chronic C6 AIS B (motor complete and sensory incomplete) spinal cord injury (SCI),1 year after injury, completed 2 blocks of LT over a 9-monthtraining period (35-session block followed by8.6 weeks of no training and then a 62-session block).Results: Before training, muscle activation was minimal for any muscle examined, whereas after the 2 blocksof LT (97 sessions), hip and knee muscle activation patterns for the bilateral rectus femoris, biceps femoris,and gastrocnemius were in phase with the kinematics. Mean EMG amplitude increased for all bilateral muscles and burst duration increased for rectus femoris and gastrocnemius muscles, whereas burst duration decreased for the biceps femoris after 62 LT sessions. Before LT, left biceps femoris had a pattern that reflected muscle stretch, whereas after training, muscle stretch of the left biceps femoris could not totally account for mean EMG amplitude or burst duration. After the62 training sessions, total BMD decreased (1.54%), and regional BMD decreased (legs: 6.72%). Total weight increased, lean mass decreased (6.6%), and fat mass increased (7.4%) in the arms, whereas fat mass decreased (3.5%) and lean mass increased (4%) in the legs.Conclusions: LT can induce positive neural and body composition changes in a nonambulatory personwith chronic SCI, indicating that neuromuscular plasticity can beinduced by repetitive locomotor trainingafter a motor complete SCI.

Muscle activation profiles about the knee during Tai-Chi stepping movement compared to the normal gait step

The purpose of this study was to investigate knee muscle activity patterns in experienced Tai-Chi (TC) practitioners during normal walking and TC stepping. The electromyographic (EMG) activity of vastus lateralis (VL), vastus medialis (VM), bicep femoris (BF), and gastrocnemius (GS) muscles of 11 subjects (five females and six males) during the stance phase of normal walking was compared to stance phase of a TC step. Knee joint motion was also monitored by using an Optotrak™motion analysis system. Raw EMG was processed by root-mean-square (RMS) technique using a time constant of 50 ms, and normalized to maximum of voluntary contraction for each muscle, referred to as normalized RMS (nRMS). Peak nRMS and co-contraction (quantified by co-contraction index) during stance phase of a gait cycle and a TC step were calculated. Paired t-tests were used to compare the difference for each muscle group peak and co-contraction pair between the tasks. The results showed that only peak values of nRMS in quadriceps and co-contraction were significantly greater in TC stepping compared to normal walking (Peak values of nRMS for VL were 26.93% for normal walking and 52.14% for TC step, p = 0.001; VM are 29.12% for normal walking and 51.93% for TC stepping, p = 0.028). Mean co-contraction index for VL–BF muscle pairs was 13.24 ± 11.02% during TC stepping and 9.47 ± 7.77% in stance phase of normal walking ( p = 0.023). There was no significant difference in peak values of nRMS in the other two muscles during TC stepping compared to normal walking. Preliminary EMG profiles in this study demonstrated that experienced TC practitioners used relatively higher levels of knee muscle activation patterns with greater co-contraction during TC exercise compared to normal walking.