Muscle size and quality of the gluteal muscles and tensor fasciae latae in women with greater trochanteric pain syndrome

Key points

1. 01Gluteus maximus (upper and lower), gluteus medius, and gluteus minimus were all significantly smaller in the GTPS group after adjusting for height
2. 02No significant difference in tensor fasciae latae volume between groups
3. 03Fatty infiltration was significantly greater in gluteus maximus upper and lower (after BMI adjustment) in the GTPS group
4. 04Posterior gluteus minimus fatty infiltration was significantly higher in GTPS, while anterior gluteus minimus infiltration was high in both groups, consistent with normal aging
5. 05Findings support targeting gluteus maximus and minimus in rehabilitation, rather than focusing solely on gluteus medius

How it was conducted

Design

Case-control study

Participants

16 women with GTPS (mean age 55.75 years) and 15 asymptomatic age-matched female controls (mean age 55.60 years)

Imaging

3.0T MRI; T1 axial images used for muscle volume tracing and Goutallier fatty infiltration rating

Muscles assessed

Gluteus maximus (upper and lower), gluteus medius, gluteus minimus, and tensor fasciae latae; anterior and posterior segments of gluteus medius and minimus also assessed separately

Primary outcomes

Muscle volume normalized to weight (cm3/kg) and fatty infiltration grade (Goutallier 0-4, dichotomized at grade 2)

Statistics

ANCOVA for volume adjusted for height; binary logistic regression for fatty infiltration adjusted for BMI

What they found

• Upper gluteus maximus volume: symptomatic 4.35 cm3/kg vs asymptomatic 5.32 cm3/kg, effect size -0.98, P = 0.01
• Lower gluteus maximus volume: symptomatic 4.07 cm3/kg vs asymptomatic 4.94 cm3/kg, effect size -0.78, P = 0.04
• Gluteus medius volume: symptomatic 3.28 cm3/kg vs asymptomatic 3.93 cm3/kg, effect size -1.15, P = 0.03
• Gluteus minimus volume: symptomatic 0.99 cm3/kg vs asymptomatic 1.29 cm3/kg, effect size -0.93, P = 0.02
• TFL volume: no significant difference, P = 0.18, effect size -0.45
• GMax upper fatty infiltration (below iliac crest) adjusted OR 1.69 (95% CI 1.08-2.66), P = 0.023
• GMax upper fatty infiltration (greater sciatic foramen) adjusted OR 1.32 (95% CI 1.04-1.66), P = 0.021
• GMax lower fatty infiltration (below circumference of femoral head) adjusted OR 1.21 (95% CI 1.00-1.46), P = 0.049
• Posterior GMin fatty infiltration (greater sciatic foramen) adjusted OR 1.24 (95% CI 1.01-1.53), P = 0.040
• Intra-rater reliability for muscle volume tracing: ICC 3,1 = 0.999
• Inter-rater agreement for fatty infiltration rating: 62.3%

Limitations

• Small sample size (n = 31 total) limits generalizability and statistical power for fatty infiltration analyses
• Study is limited to women, so findings cannot be applied to men
• Only unilateral limbs were assessed, preventing analysis of within-person asymmetry
• Inter-rater agreement for fatty infiltration was only 62.3%, introducing measurement uncertainty despite use of a third examiner for disagreements

Why it matters

For patients

Women with lateral hip pain may have weaker and smaller gluteal muscles, particularly gluteus maximus and minimus, which could explain gait difficulties and pain with daily activities.

For clinicians

Rehabilitation for GTPS should include targeted strengthening of gluteus maximus and minimus, not just gluteus medius, given the atrophy and fatty infiltration pattern identified in this study.

For readers

This small case-control study provides imaging evidence that GTPS involves broader gluteal muscle changes than previously recognized, shifting the rehabilitation focus toward gluteus maximus and minimus.