Comparison of gluteus medius and minimus activity during gait in people with hip osteoarthritis and matched controls.

The gluteal muscles act as stabilizers of the hip joint and are important for the maintenance of hip function. Atrophy and weakness of the gluteal muscles have been identified in people with hip OA, but it is not known whether these muscles also exhibit altered activity patterns. The aim of this study was to compare gluteal muscle activity in people with hip OA and healthy older adults. Fine-wire intramuscular electrodes were inserted into the three segments of gluteus medius (GMed) and two segments of gluteus minimus (GMin) in 20 participants with unilateral hip OA and 20 age- and gender-matched controls. Electromyographic activity of these muscle segments was examined during walking along a 10 m walkway. Peak amplitude, average amplitude, and time to peak were compared between groups during the stance phase of the gait cycle. During early stance, the OA group demonstrated a higher burst of activity in posterior GMin (P = 0.02) and trends toward a higher peak in anterior GMin. Both groups displayed peak activity in anterior GMin in the early stance phase in contrast to previous reports in young adults. This early burst of muscle activity was more pronounced with increasing severity of OA. No differences were identified in GMed activity. While altered GMin activity is associated with aging, these changes were more pronounced in participants with hip OA. To reduce disability associated with hip OA, future rehabilitation programs should consider targeted gait strategies and exercises for GMin.