The size and prevalence of bony hip morphology does not differ between football players with and without hip and/or groin pain: findings from the FORCe cohort

Key points

1. 01Cam morphology prevalence did not differ between symptomatic and pain-free football players
2. 0276% of male hips and a substantial proportion of female hips without pain had cam morphology
3. 03Women with hip and groin pain had a slightly larger alpha angle on the Dunn view than pain-free women, but clinical significance is uncertain
4. 04Pincer morphology and acetabular dysplasia were rare in both groups (around 4-8% and 3-4% respectively)
5. 05No association was found between alpha angle or LCEA and patient-reported hip outcome scores in football players or men

How it was conducted

Design

Case-control study (baseline data from the FORCe prospective cohort)

Participants

Sub-elite football players (soccer and Australian football) recruited in Melbourne and Brisbane, Australia, between August and October; symptomatic group had self-reported hip and/or groin pain >duration threshold and a positive FADIR test; control group had no pain and a negative FADIR test

Imaging

Supine anteroposterior pelvis and Dunn radiographs for each hip; alpha angle and lateral centre-edge angle (LCEA) measured using statistical shape modelling software

Morphology thresholds

Cam morphology: alpha angle >60 degrees; large cam: alpha angle >78 degrees; pincer morphology: LCEA >40 degrees; acetabular dysplasia: LCEA <20 degrees

Primary outcome

Continuous alpha angle (size of cam morphology) compared between symptomatic and control hips using generalised estimating equations

Patient-reported outcomes

iHOT-33 (quality of life) and HAGOS pain and symptoms subscales completed by all participants

What they found

• In all football players, alpha angle did not differ between symptomatic and control hips on either the AP or Dunn view (between-group differences not statistically significant)
• Cam morphology prevalence did not differ between symptomatic and pain-free hips in football players overall or in men
• 76% of male hips without pain had cam morphology; prevalence of large cam morphology in men ranged from approximately 30-40% across symptom groups with no significant difference
• Women with hip and/or groin pain had a slightly larger Dunn alpha angle compared to control hips (difference 5.9 degrees; 95% CI: approximately 1.2 to 10.6, P=0.02), but not on the AP view
• Pincer morphology prevalence was similar between groups (approximately 7% symptomatic vs 8% control in football players overall)
• Acetabular dysplasia was rare in both groups (approximately 4% symptomatic vs 3% control)
• No association between alpha angle (AP or Dunn) and iHOT-33 or HAGOS in all football players or in men
• In women, LCEA was associated with HAGOS-P (r = -0.43; 95% CI: -0.72, -0.04, P = 0.03), indicating greater acetabular coverage was associated with higher pain levels

Limitations

• The FADIR test has poor specificity, so findings cannot be assumed specific to intra-articular hip pathology; adductor-, iliopsoas-, pubic-, and inguinal-related groin pain may have contributed to symptoms
• Radiographs provide only 2D visualisation and may underestimate cam morphology size and prevalence compared to MRI or CT
• Risk of selection bias as both groups responded to study advertisements and may not represent all football players
• Small number of female football players may have limited ability to detect differences in bony morphology between symptom groups in women

Why it matters

For patients

Having a cam-shaped hip does not mean you will develop hip or groin pain, as most pain-free football players also have this bony feature.

For clinicians

Imaging findings of cam or pincer morphology should not be used in isolation to explain hip and groin pain in football players; other pain sources including adductor- and pubic-related pathology need careful evaluation.

For readers

This study challenges the assumption that bony hip shape drives symptoms and highlights that physical activity level and other factors may be equally or more important in symptom development.