Does hip muscle strength and functional performance differ between football players

Key points

1. 01101 sub-elite football players (soccer and Australian football) were compared: 50 with hip dysplasia, 51 controls
2. 02No significant difference was found in any of 8 hip muscle strength measures or 3 functional performance tests
3. 03Results were not modified by sex or age
4. 04The hip dysplasia group had substantially worse patient-reported pain and function scores (HAGOS, iHOT) despite similar physical capacity
5. 05Participation in football may preserve muscle strength and functional performance in people with hip dysplasia

How it was conducted

Design

Observational cross-sectional study using baseline data from the FORCe (Femoroacetabular Impingement and Hip OsteoaRthritis Cohort) longitudinal study

Participants

101 sub-elite football players (soccer and Australian football) aged 18-50 years recruited in Melbourne and Brisbane, Australia, between August 2015 and October 2018

Groups

Hip dysplasia (HD) group: 50 players with hip/groin pain, positive FADIR test, and radiographic LCEA <25 degrees (59 hips); Control group: 51 asymptomatic players with LCEA 25-40 degrees (87 hips)

Hip muscle strength

Isometric strength (flexion, extension, abduction, adduction, internal rotation, external rotation) and eccentric strength (abduction, adduction) measured by hand-held dynamometry; normalised to Nm/kg

Functional performance

Single-leg hop for distance (cm), side bridge endurance (seconds), single-leg rise test (repetitions)

Analysis

Linear regression with generalised estimating equations (GEE) controlling for age and sex; interaction terms tested for sex as effect modifier

What they found

• Isometric hip abduction: HD 1.34 Nm/kg (95% CI 1.28-1.4) vs Control 1.37 Nm/kg (95% CI 1.23-1.45); Estimate 0.03 (95% CI -0.07 to 0.13), P = 0.579
• Isometric hip adduction: HD 1.34 Nm/kg (95% CI 1.25-1.43) vs Control 1.37 Nm/kg (95% CI 1.27-1.47); Estimate 0.04 (95% CI -0.1 to 0.17), P = 0.597
• Eccentric hip abduction: HD 1.59 Nm/kg (95% CI 1.48-1.69) vs Control 1.62 Nm/kg (95% CI 1.5-1.73); Estimate 0.03 (95% CI -0.13 to 0.18), P = 0.714
• Eccentric hip adduction: HD 1.73 Nm/kg (95% CI 1.60-1.86) vs Control 1.86 Nm/kg (95% CI 1.73-1.99); Estimate 0.13 (95% CI -0.05 to 0.32), P = 0.158
• Hip external rotation: HD 0.53 Nm/kg (95% CI 0.49-0.56) vs Control 0.53 Nm/kg (95% CI 0.48-0.57); Estimate 0.00 (95% CI -0.05 to 0.06), P = 0.918
• Hip internal rotation: HD 0.48 Nm/kg (95% CI 0.44-0.51) vs Control 0.48 Nm/kg (95% CI 0.44-0.52); Estimate 0.01 (95% CI -0.05 to 0.06), P = 0.768
• Hip flexion: HD 1.00 Nm/kg (95% CI 0.93-1.09) vs Control 0.96 Nm/kg (95% CI 0.88-1.05); Estimate -0.04 (95% CI -0.16 to 0.07), P = 0.457
• Hip extension: HD 1.56 Nm/kg (95% CI 1.46-1.67) vs Control 1.43 Nm/kg (95% CI 1.32-1.54); Estimate -0.13 (95% CI -0.29 to 0.02), P = 0.087
• Single-leg hop for distance: HD 135 cm (95% CI 128.4-140.8) vs Control 136 cm (95% CI 129.63-141.85); Estimate 1.15 (95% CI -7.47 to 9.76), P = 0.794
• Single-leg rise: HD 24 reps (95% CI 20.6-27.3) vs Control 26.1 reps (95% CI 22.26-29.92); Estimate 2.13 (95% CI -2.95 to 7.21), P = 0.411
• Side bridge endurance: HD 89 s (95% CI 80.77-97.73) vs Control 86.7 s (95% CI 77.23-96.14); Estimate -2.48 (95% CI -15.02 to 10.06), P = 0.698
• No relationships were modified by sex or age for any strength or functional performance measure

Limitations

• Cross-sectional design prevents causal inference - it is unknown whether football participation causes preserved strength or whether stronger individuals are more likely to continue playing
• The study may have been underpowered to detect sex as an effect modifier, given that only 26-27% of participants were female
• Hip dysplasia diagnosis criteria lack international consensus - debate remains about LCEA thresholds (20 vs 25 degrees), supine vs standing radiograph position, and the role of the FADIR test
• Findings may not generalise beyond sub-elite football players with relatively mild dysplasia and no radiographic osteoarthritis

Why it matters

For patients

People with hip dysplasia who continue to play football can be reassured that their hip strength and physical function are likely to be comparable to players without dysplasia, though pain and quality of life may still be meaningfully affected.

For clinicians

Clinicians should not assume hip muscle weakness or functional deficits in active football players with hip dysplasia, especially if disease is not advanced; assessment of patient-reported outcomes remains important as these differ substantially from controls.

For readers

This is an early exploratory study in an under-researched population; prospective longitudinal data are needed to establish whether continued sport participation genuinely protects physical function in hip dysplasia.