Development and internal validation of the hypermobile lateral meniscus score (HLMS): A diagnostic model for isolated...

A subset of patients presenting with persistent rotational knee symptoms demonstrates normal or equivocal magnetic resonance imaging despite clinically significant lateral meniscal instability, making preoperative diagnosis of isolated hypermobile lateral meniscus (HLM) challenging.

To develop and internally validate the Hypermobile Lateral Meniscus Score (HLMS), a multivariable diagnostic model for the preoperative identification of arthroscopically confirmed isolated HLM.

A retrospective multicenter diagnostic cohort study screened 214 consecutive patients undergoing knee arthroscopy for persistent lateral compartment symptoms between 2019 and 2023. After exclusion of 64 patients according to prespecified eligibility criteria, 150 consecutively eligible patients were retained for analysis. No diagnostic-group matching, quota sampling, or post hoc subsampling was performed. Arthroscopic reference-standard assessment classified 50 patients as having isolated HLM, 50 as having structural lateral meniscal tears without hypermobility, and 50 as symptomatic controls who underwent arthroscopy for persistent lateral compartment symptoms after failed nonoperative treatment but demonstrated neither a structural lateral meniscal lesion nor pathological dynamic instability during standardized arthroscopic assessment. Candidate predictors were restricted to preoperative demographic, clinical, patient-reported, and magnetic resonance imaging (MRI) variables and were evaluated using penalized multivariable logistic regression; arthroscopic findings were used exclusively for reference-standard classification and were not entered into model development. Model discrimination was assessed using the area under the receiver operating characteristic (ROC) curve, whereas calibration was evaluated using calibration plots, calibration slope, calibration intercept, and the Brier score. Internal validation was performed using 1000 bootstrap resamples.

Six predictors were retained in the final model, including MRI-clinical discordance, painful rotational catching, posterolateral giving-way, pain during deep flexion, popliteomeniscal fascicle attenuation on MRI, and participation in pivoting sports. The simplified 0-12-point HLMS demonstrated excellent discrimination, with an apparent area under the ROC curve of 0.902 (95% confidence interval [CI], 0.86-0.96) and an optimism-corrected bootstrap area under the ROC curve of 0.890. Diagnostic sensitivity was 88%, specificity was 86%, positive and negative likelihood ratios were 6.29 and 0.14, respectively, and calibration remained excellent (calibration slope, 0.97; Brier score, 0.087), indicating minimal model optimism.

The Hypermobile Lateral Meniscus Score demonstrated excellent discrimination and stable internally validated performance within this selected symptomatic arthroscopy cohort. External validation is required before routine clinical implementation.

Level III, retrospective diagnostic cohort study.