Objectives: Hip microinstability is increasingly being accepted and recognized as a cause of hip pain and dysfunction in young, active patients. Part of the slow acceptance and under-recognition of hip microinstability has been difficulty in understanding the hip examination in those with non-arthritic hip pain, as well as the lack of validated diagnostic criteria. As a result, we performed an international multicenter prospective evaluation of patients undergoing hip arthroscopy to identify clinical predictors of hip microinstability. Methods: Several international hip arthroscopists convened to identify clinical features from history, physical examination and imaging that have been, or potentially could be, clues to the diagnosis of hip microinstability. Then, 3 surgeons from 3 sites agreed to evaluate all patients undergoing hip arthroscopy, including all 184 agreed upon variables, as part of their normal work up. A retrospective analysis was conducted on these prospectively evaluated patients who underwent arthroscopic surgery for intra-articular hip pathology between May 2022 and March 2025 across these sites. Comprehensive demographic and clinical data were extracted from medical records, including symptom duration, sport participation, physical examination findings, family history, and imaging metrics. Intraoperative findings were recorded. The diagnosis of hip microinstability was made based on published criteria of surgical findings. Patients with total hip arthroplasty, hip arthritis of Tonnis grade 2 or more, avascular necrosis, rheumatologic arthritis, pigmented villonodular arthritis, Perthes disease or slipped capital femoral epiphysis were excluded, as were patients who underwent extra-articular hip procedures. Bivariate differences in demographics and clinical variables between those with and without HM were analyzed using two-sample t-tests, chi-square tests, and Fisher’s exact tests. Analyses were completed in RStudio using a two-sided level of significance of 0.05. Results: A combined 802 patients (405 female – 50.5%) with an average age of 34.4 (+ 11.4) underwent hip arthroscopy during the study period; 240 (30%) were confirmed to have intraoperative microinstability. These patients were predominantly female (78%). A history of developmental dysplasia of the hip (DDH) was present in 12.6% of instability patients (vs 4% of those without HM). The mean Beighton score was significantly higher in instability patients (2.7) compared with those without HM (1.2), indicating greater generalized joint hypermobility. There was no statistically significant difference in location of hip pain, mechanical symptoms or popping, clicking or sensation of instability between the HM group and those without hip microinstability. On physical examination, hip range of motion was increased in microinstability patients, with higher average hip flexion (117° vs. 108°), seated external rotation (38° vs. 34°), and seated internal rotation (27° vs. 23°) as measured using an electronic goniometer compared to those without instability. Stress tests, such as the hyperextension-external rotation test (p<0.001), the abduction-extension-external rotation test (p<0.001), the prone external rotation test (p=0.021), the prone apprehension-relocation test (p=0.015 for apprehension, but p=0.07 for pain), and the feeling of pain (p= 0.033) or apprehension (p=0.001) with the axial distraction test were also positive in patients with microinstability statistically more often than in non-instability patients. Imaging findings revealed a higher prevalence of the Cliff sign in instability patients (34% vs. 23%). Instability patients also demonstrated lower lateral center-edge angles (29.1° vs. 30.7°), decreased anterior center-edge angles (ACEA: 32.0° vs. 35.2°), and increased Tönnis angles (5.3° vs. 3.6°). Notably, 16.8% of patients with hip microinstability had normal femoral anteversion compared to only 2.9% of those without instability. Conclusions: Microinstability was bivariately associated with female sex, a prior dysplasia diagnosis, a higher Beighton score, larger range of motion (flexion, seated and prone ER/IR), smaller LCEA and ACEA, larger Tonnis angle, and Cliff sign. There was no difference when the patients were queried about location of hip pain, presence of mechanical symptoms or symptoms such as popping or clicking, or sensation of instability between those with surgically confirmed hip microinstability and those without instability. This study contributes valuable insights into the clinical presentation of patients with hip microinstability, and may help the clinician identify this entity more confidently and readily.
Mbchb et al. (Fri,) studied this question.