Elbow Microinstability: From the State of the Art to an Integrated Clinical Approach

Lateral elbow pain is a common condition often misattributed solely to tendinopathy, while subtle instability may represent a significant underlying cause. Traditional classifications of elbow instability primarily address traumatic or grossly unstable patterns, leaving minor forms underrecognized. Recent evidence has emphasized the role of the Radial-Lateral Collateral Ligament (R-LCL) in maintaining joint stability, and its elongation has been linked to Symptomatic Minor Instability of the Lateral Elbow (SMILE). This model describes a horizontal type of radiocapitellar instability, where ligamentous incompetence leads to compensatory overload of the extensor carpi radialis brevis, ultimately producing chronic pain. Advances in diagnostic tools-including dynamic ultrasound (HELP-US test), CT arthrography with the SMILE Index, and arthroscopic signs such as the Loose Collar Sign-have improved recognition of this condition. However, surgical controversies remain, particularly regarding the potential destabilizing role of lateral release in patients with unrecognized R-LCL pathology. Arthroscopic stabilization techniques, such as R-LCL plication or imbrication, have shown promising outcomes, offering pain relief and functional recovery with minimally invasive approaches. This review integrates anatomical, biomechanical, and clinical evidence into a structured diagnostic and therapeutic algorithm, aiming to reduce diagnostic uncertainty and guide tailored interventions. Recognition of microinstability, and, in particular, the SMILE model, is crucial to optimize management of patients with chronic lateral elbow pain refractory to conservative measures.