Defining the Minimal Clinically Important Difference (MCID), Patient Acceptable Symptom State (PASS), and Maximal Outcome Improvement (MOI) values for individuals with acetabular dysplasia (AD) undergoing non-operative management.

Retrospective review of prospectively collected data from two hip-preservation surgery centers. 45 individuals (42 female, mean age 16.5 years, range 10–35) with x-ray-confirmed acetabular dysplasia (lateral center edge angle < 25 degrees, Tonnis angle > 14 degrees) completed 8–10 weeks of physiotherapy. PT was not standardized; patients chose their own provider. The iHOT-12 (0–100 scale, higher = better function) was completed at baseline and at 8–10-week follow-up, along with a yes/no satisfaction question. The MCID was calculated as half the standard deviation of the change score. PASS change, absolute PASS, and MOI thresholds were derived using ROC analysis with Youden's index to maximize sensitivity and specificity.

Mean iHOT-12 scores were 41.61 (SD 16.0) at baseline and 49.00 (SD 23.5) after 8–10 weeks of PT. The MCID was 8.5 points. The PASS change score was 15.2 with sensitivity .77 and specificity .78. The absolute PASS threshold was 62 with sensitivity .62 and specificity .87. The MOI was 22.9% with sensitivity .69 and specificity .88. 64.4% of participants achieved the MCID while 37.8% achieved the PASS change score. 32 of 45 (71.1%) were not satisfied with their current function; 13 (28.9%) were.

You now have specific numbers to interpret iHOT-12 scores in your AD patients: a gain of 8.5 points after 8–10 weeks is a meaningful change, a score of 62 or above means the patient considers their state acceptable, and a 22.9% improvement from their personal best is the MOI. Use these to set goals and track progress, but also to manage expectations — most patients will show meaningful improvement, yet few will feel fully satisfied, because the underlying bony shape cannot be corrected by exercise. A conversation about realistic outcomes is part of the treatment.

Physiotherapy was not standardized — patients used their own PT providers, so the specific exercises, dosage, and approaches varied widely across the 45 participants. The sample was 45 people, 42 of them female, mean age 16.5 years. This tells you little about older patients, males with AD, or those with more severe deformity. Data came from two specialized hip-preservation centers, which may not reflect what happens in a community PT clinic or a general orthopedic practice. The thresholds only apply to an 8–10-week PT trial for a specific AD population; they may not hold for longer rehabilitation periods, different hip conditions, or patients not seen by a hip-preservation surgeon. The satisfaction anchor question was chosen by the study team rather than validated independently, and the study could not define a smallest clinically better (SCB) value.

The authors declared no conflicts of interest related to this research.

Do not read the 64.4% MCID achievement as evidence that physiotherapy resolves acetabular dysplasia. The study defines measurement thresholds, not treatment efficacy; the underlying bony undercoverage cannot be corrected by exercise, and only 29% of patients reported being satisfied with their hip function after the trial.