Hip
Hip dysplasia
Acetabular dysplasia is quantified with the lateral centre-edge angle and the Tönnis angle read together, because a borderline centre-edge angle behaves very differently depending on whether the weight-bearing zone is horizontal or steeply upsloping.
What you are actually deciding
A centre-edge angle between 18 and 25 degrees is the contested range. Read it with the Tönnis angle: above 10 degrees suggests a genuinely unstable hip, while a horizontal sourcil suggests the coverage is adequate despite the borderline number.
Patient-reported outcome measure3
- HOOS Calculator40 itemsHip disability and Osteoarthritis Outcome ScoreThe HOOS is a 40-item patient-reported questionnaire that scores hip function as five separate subscales — Symptoms, Pain, Activities of Daily Living, Sport and Recreation, and Hip-related Quality of Life — each from 0 (extreme problems) to 100 (no problems).
- HOS Calculator26 itemsHip Outcome ScoreThe Hip Outcome Score is a 28-item patient-reported questionnaire for non-arthritic hip conditions that yields two independent percentage scores — an Activities of Daily Living subscale, administered as 19 questions of which 17 are scored, and a 9-item Sports subscale — each running from 0% (unable to perform the listed activities) to 100% (no difficulty at all).
- Oxford Hip Score12 itemsOxford Hip ScoreThe Oxford Hip Score is a 12-item patient-reported questionnaire about hip pain and everyday function over the past four weeks, each item scored 0 to 4 and summed to a total of 0 to 48 in which 48 represents the best possible hip — it is licensed by Oxford University Innovation, so the item wording is not reproduced here.
Clinical calculator2
- LCEA Calculator1 itemsLateral Centre-Edge Angle of WibergThe lateral centre-edge angle measures how far the acetabulum covers the femoral head laterally on an anteroposterior pelvis radiograph, where below 18 degrees indicates frank dysplasia, 18 to 25 degrees is borderline, 25 to 39 degrees is normal, and 40 degrees or more indicates overcoverage.
- Tönnis Angle1 itemsTönnis Angle (Acetabular Index of the Weight-Bearing Zone)The Tönnis angle measures the slope of the acetabular weight-bearing zone on an anteroposterior pelvis radiograph, where 0 to 10 degrees is normal, above 10 degrees indicates a steep upsloping roof associated with dysplasia and instability, and a negative angle indicates overcoverage.
Classification system1
Thresholds that apply here
Published change thresholds across the instruments above. Check the population matches your patient before using a value — a threshold derived in a different cohort will mislead you.
| Instrument | Type | Value | Subscale | Population |
|---|---|---|---|---|
| HOOS | MCID | 10 points | All subscales | Total hip arthroplasty |
| HOOS | MCID | ~9 points | Pain | Hip osteoarthritis, non-surgical |
| HOOS | PASS | ~73 points | Pain | Hip arthroscopy for FAI |
| HOOS | MDC | 10–16 points | Varies by subscale | Hip osteoarthritis |
| HOS | PASS | ≈ 87% | Activities of Daily Living | Arthroscopic surgery for femoroacetabular impingement |
| HOS | PASS | ≈ 75% | Sports | Arthroscopic surgery for femoroacetabular impingement |
See the full threshold database for every instrument on the site.