Relationship between hip and groin pain and hip range of motion in amateur soccer and Australian rules football players

Key points

1. 01Internal rotation ROM was lower in symptomatic hips only when cam morphology was present (adjusted mean difference -4.5 degrees), not when cam was absent
2. 02Symptomatic women had lower total rotation ROM than asymptomatic women (adjusted mean difference -8.2 degrees), but no such difference was seen in men
3. 03Symptomatic men had reduced bent-knee fall-out ROM compared with controls (adjusted mean difference 1.6 cm), but women showed no difference
4. 04Flexion and external rotation ROM did not differ between symptomatic and asymptomatic hips in either sex
5. 05Clinicians should account for cam morphology status and sex when interpreting hip ROM findings in this population

How it was conducted

Design

Cross-sectional study (Level of evidence 3), part of the FORCe prospective cohort

Participants

184 symptomatic amateur soccer and Australian Rules football players (276 hips) and 50 matched asymptomatic controls (98 hips); 20-28% women; median age 26 years

Symptomatic criteria

Hip or groin pain >6 months, pain >=3/10 on NRS with sport-specific movements, positive FADIR test, Kellgren-Lawrence grade <2

ROM measures

Active hip flexion, passive internal and external rotation at 90 degrees flexion, total rotation (sum of IR and ER), and bent-knee fall-out (BKFO)

Cam morphology

Defined as alpha angle >=60 degrees on AP pelvis or 45-degree Dunn radiograph; present in 71% of symptomatic and 61% of control hips

Statistical analysis

Linear regression with generalized estimating equations; interaction terms for group x cam and group x sex; confounders age, sex, and cam morphology

What they found

• Symptomatic hips with cam morphology had less internal rotation ROM than controls with cam morphology: adjusted mean difference -4.5 degrees (95% CI -7.4 to -1.6 degrees; P=0.029)
• Internal rotation ROM did not differ between symptomatic and control hips without cam morphology: adjusted mean difference -1.0 degrees (95% CI -4.6 to 2.6 degrees; P=0.579)
• Symptomatic women had lower total rotation ROM than asymptomatic women: adjusted mean difference -8.2 degrees (95% CI -14.1 to -2.2 degrees; P=0.036)
• Total rotation ROM did not differ between symptomatic and asymptomatic men: adjusted mean difference -1.8 degrees (95% CI -5.4 to 1.8 degrees; P=0.322)
• Symptomatic men had higher BKFO values (indicating lower ROM) than controls: adjusted mean difference 1.6 cm (95% CI 0.3 to 3.0 cm; P=0.022)
• BKFO did not differ between symptomatic and asymptomatic women: adjusted mean difference -1.5 cm (95% CI -3.73 to 0.8 cm; P=0.176)
• Flexion ROM: pain group mean 101.2 degrees (95% CI 100.0-102.3) vs control 103.3 degrees (95% CI 101.2-105.5); P=0.078 (non-significant)
• External rotation ROM: pain group mean 41.7 degrees (95% CI 39.4-43.9) vs control 41.4 degrees (95% CI 40.2-42.7); P=0.865 (non-significant)

Limitations

• The FADIR test has poor specificity, so extra-articular pain sources cannot be excluded and findings may not be specific to intra-articular hip pathology
• Women comprised only 20% of the cohort, which may have underpowered detection of additional sex-related interactions
• All participants were still playing sport despite symptoms, limiting generalisability to more severe presentations or non-athletic populations
• Other bony variables (femoral torsion, acetabular version) and additional ROM measures (abduction, sport-specific combined movements) were not assessed

Why it matters

For patients

Patients with hip or groin pain and cam morphology on imaging are likely to have reduced internal rotation, which may be a meaningful target in their rehabilitation.

For clinicians

ROM testing remains clinically worthwhile but must be interpreted in light of cam morphology status and patient sex; a 4.5-degree internal rotation deficit (with cam) and an 8.2-degree total rotation deficit (women) exceed measurement error and are likely clinically important.

For readers

This study clarifies why prior research has conflicted: pooling patients regardless of cam morphology and sex obscures real ROM differences that emerge only within specific subgroups.