Detection of Gluteal Changes Using Ultrasound Imaging During Phases of Gait in Individuals With Medial Knee Displacement.

Context : Medial knee displacement (MKD) is a common risk factor for lower-extremity injury and is related to altered gluteal muscle activity. Ultrasound imaging (USI) is a reliable means to explore mechanical muscle activity; however, no information exists regarding USI of the gluteals during gait in an MKD population. Objective : To determine differences in USI gluteal muscle activity during gait in individuals with and without MKD. Design : Descriptive laboratory study. Setting : University research laboratory. Participants : Out of 28 participants, 14 exhibiting MKD unilaterally during a single-leg squat (19.36 [1.51] y, 169.73 [7.50] cm, and 62.01 [10.57] kg; 10 females) and 14 matched non-MKD subjects (20.29 [1.73] y, 167.24 [9.07] cm, and 67.53 [16.03] kg). Interventions : Bilateral B-mode USI of the gluteus maximus (Gmax) and gluteus medius (Gmed) muscles during quiet stance, heel strike, and a 10-second treadmill walking clip. Main Outcome Measures : Gluteal thickness measures normalized to quiet stance yielded activity ratios, and percentage of muscle thickness change was assessed between heel strike and quiet stance. Differences between groups were assessed with Cohen's d effect sizes with 95% confidence intervals. Activity ratios with 90% confidence intervals plotted on 10% intervals from 0% to 100% of gait were used to compare groups and limbs. A subsample of images was measured to determine intertester reliability. Results : USI revealed decreased Gmax and Gmed percent change at heel strike (%change = -9.57% [7.15%] and -8.76% [4.26%], respectively). The MKD limb compared with the contralateral limb exhibited decreased Gmed activity ratio at 30% of gait (MKD = 0.89 [0.056]; non-MKD = 1.01 [.052]). Intertester reliability was excellent for gluteus maximus (intraclass correlation coefficient = .987 [.014]) and Gmed (intraclass correlation coefficient = .989 [.013]) measurements. Conclusions : USI highlighted gluteal activity differences of MKD limbs during gait, which may contribute to inadequate hip stabilization during this daily repetitive task. These findings potentiate the use of USI as an intervention- or screening-based visual tool.