The effect of chronic low back pain and lumbopelvic stabilization instructions on gluteus medius activation during sidelying hip movements.

BACKGROUND: People with chronic low back pain (LBP) often demonstrate altered muscle activation with movements that involve the lumbopelvic region and hips. OBJECTIVE: The purpose of this study was to compare gluteus medius activity during sidelying hip abduction (SHA) and sidelying hip abduction-lateral rotation (SHALR) with and without instruction for lumbopelvic stabilization in people with and without chronic LBP. METHODS: A cross-sectional study was conducted recruiting participants with (n = 17) and without (n = 17) chronic LBP. Gluteus medius activity was recorded with surface electromyography during the performance of SHA and SHALR with and without instructions including the abdominal drawing-in maneuver for lumbopelvic stabilization. RESULTS: For SHA and SHALR, there was a significant main effect for instruction for stabilization indicated by a decrease in gluteus medius activity with instructions (p = .001, p < .001). There was not a significant main effect of chronic LBP on gluteus medius activity between groups for either activity. There was no significant interaction effect of pain and instruction for stabilization with SHA or SHALR. CONCLUSION: Knowledge of changes in gluteus medius muscle activation patterns with trunk stabilization instruction may help clinicians with assessment of exercise performance to optimize gluteus medius activation.

Tibiofemoral Rotation During Sit-to-Stand Activity After TKA.

The objective of this study was to describe how tibiofemoral internal/external rotation varies in patients after total knee arthroplasty (TKA) when compared with control participants during a sit-to-stand (STS) maneuver. Motion analysis was used to measure internal/external knee rotation during STS in the control and TKA groups. Fourteen participants were included in the study. Six patients with 7 TKA knees (6 posterior stabilized and 1 cruciate-retaining TKA) were compared with 8 control participants with 8 knees from the current authors' laboratory database. Participants performed 3 STS maneuvers, and the average internal/external rotation of the femur with respect to the tibia was compared. All control participants and 2 TKA participants had internal rotation of the femur with respect to the tibia, whereas 4 TKA participants had external rotation, and 1 had no rotation during STS. Further investigation into the surgical and patient- and implant-related factors that affect this resulting reverse kinematic profile seems to be warranted. [Orthopedics. 2016; 39(3):S41-S44.].

Increased hip abduction in high body mass index subjects during sit-to-stand.

Obesity is associated with increased risk of total hip arthroplasty (THA) dislocation. Differences in kinematics and kinetics at the hip during activities of daily living such as sit-to-stand (STS) may contribute to this risk. Nine high body mass index (BMI) subjects (mean BMI 31.2) and ten normal BMI control subjects (mean BMI 22.1) were analyzed using force plates and an optoelectronic motion capture camera system during controlled STS movement. Flexion/extension, abduction/adduction, and internal/external rotation angles and moments at the hip and knee were calculated using a musculoskeletal model. No differences were found at the knee. Peak hip abduction angles were on average 50% greater in the high BMI group compared to the normal group (p=0.038). The hip was roughly 50% more abducted throughout the entire STS cycle in the high BMI group. Peak normalized hip abduction moments were approximately twice as large in the high BMI group (p=0.005). Further research is required to determine if this increase in abduction angle and moment observed during STS is a contributor to risk for complications following THA in obese subjects.