This 1993 cadaveric study quantifies how compression of the humeral head into the glenoid concavity stabilizes the joint against translating forces. Using 10 fresh-frozen shoulders with capsule removed, the authors tested stability ratios in eight directions before and after labral resection at two compressive loads. The study defines the biomechanical basis of concavity-compression as the dominant mid-range stabilizing mechanism.
Before this paper, glenohumeral stability was attributed almost entirely to the capsule and ligaments — structures that are demonstrably lax through most of the functional range of motion. Lippitt et al. Provided the first quantitative proof that concavity-compression, driven by rotator cuff muscle force, is the dominant stabilizer in mid-range, filling that explanatory gap.
When you see a patient with multidirectional instability and mid-range laxity, this paper is why you start with rotator cuff strengthening: more compressive load directly and proportionally increases the translating force the joint can resist. Prescribing physio is not just empirical. It has a measurable biomechanical mechanism.
When you see a patient with a Bankart lesion, this paper quantifies why labral repair is not optional: the labrum contributes ~20% of concavity-compression stability on average, and up to 37% inferiorly. Restoring labral depth restores the concavity, not just the capsuloligamentous anchor.
The linear relationship between glenoid depth and stability ratio is the conceptual foundation for glenoid bone loss thresholds in recurrent instability. Loss of anterior glenoid rim. Already the shallowest direction. Disproportionately erodes the concavity-compression reserve, which is why the inverted-pear glenoid is a surgical indication for bone grafting rather than soft-tissue repair alone.
This 1993 cadaveric study quantifies how compression of the humeral head into the glenoid concavity stabilizes the joint against translating forces. Using 10 fresh-frozen shoulders with capsule removed, the authors tested stability ratios in eight directions before and after labral resection at two compressive loads. The study defines the biomechanical basis of concavity-compression as the dominant mid-range stabilizing mechanism.
Before this paper, glenohumeral stability was attributed almost entirely to the capsule and ligaments — structures that are demonstrably lax through most of the functional range of motion. Lippitt et al. Provided the first quantitative proof that concavity-compression, driven by rotator cuff muscle force, is the dominant stabilizer in mid-range, filling that explanatory gap.
When you see a patient with multidirectional instability and mid-range laxity, this paper is why you start with rotator cuff strengthening: more compressive load directly and proportionally increases the translating force the joint can resist. Prescribing physio is not just empirical. It has a measurable biomechanical mechanism.
When you see a patient with a Bankart lesion, this paper quantifies why labral repair is not optional: the labrum contributes ~20% of concavity-compression stability on average, and up to 37% inferiorly. Restoring labral depth restores the concavity, not just the capsuloligamentous anchor.
The linear relationship between glenoid depth and stability ratio is the conceptual foundation for glenoid bone loss thresholds in recurrent instability. Loss of anterior glenoid rim. Already the shallowest direction. Disproportionately erodes the concavity-compression reserve, which is why the inverted-pear glenoid is a surgical indication for bone grafting rather than soft-tissue repair alone.