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What Are the Biomechanical Features and Metrics for Native Hip Instability? Consensus Statements From a Scoping
Moritz Wagner1, Andrew E Anderson2, Ariane Parisien3
1Division of Orthopaedic Surgery, University of Ottawa, Ottawa, Ontario, Canada.
Clinical Orthopaedics and Related Research
|March 30, 2026
Summary
Native hip instability involves abnormal motion influenced by bone, ligaments, and muscles. Femoral head translation under 3 mm is considered normal, but current metrics cannot reliably distinguish between types of instability.
Area of Science:
- Orthopedics
- Biomechanics
- Sports Medicine
Background:
- Native hip instability presents a spectrum of abnormal pathomechanics under physiological loading, leading to pain and dysfunction.
- It encompasses conditions from hip dysplasia to femoroacetabular impingement and instability without bony deformities.
- Current biomechanical definitions, thresholds, and metrics for hip instability remain inconsistent.
Purpose of the Study:
- To map available evidence on the biomechanical features of native hip instability.
- To identify knowledge gaps in understanding hip instability.
- To explore whether current biomechanical metrics can reliably differentiate various degrees of instability.
Main Methods:
- A scoping review and modified Delphi technique consensus study involving 100 international experts.
- Statements on biomechanical features and metrics were developed following a rapid scoping review.
- Consensus was defined as ≥ 75% agreement across two Delphi rounds.
Main Results:
- Anatomic features include bony morphology, static capsulolabral stabilizers, and dynamic muscular stabilizers.
- Femoral head translation < 3 mm was identified as a normal metric by consensus.
- Insufficient evidence exists to differentiate between microinstability and conventional (bony) instability.
Conclusions:
- Native hip instability is characterized by unpredictable femoral head motion influenced by bony morphology, capsulolabral integrity, and muscular stabilization.
- Femoral head translation < 3 mm is considered physiological; however, current methods cannot reliably differentiate instability types.
- Standardized in vivo 3D hip motion measurements are needed to establish clinically meaningful thresholds and guide patient care.
