Introduction: The metacarpophalangeal joint (MCPJ) of the long fingers is essential for various hand functions. Joint kinematics are complex, involving flexion-extension, lateral movements, and axial rotation. During these motions, different joint stresses occur. The long finger MCPJ operates through a balance between mobility on one hand and stability and joint congruence on the other. Anatomical structures ensuring this balance through adaptive biomechanical mechanisms include the articular surfaces, which provide minimal stabilization except at the terminal degrees of flexion; the capsulo-ligamentous system, which acts as the primary stabilizer by maintaining constant joint tension; and the musculo-tendinous system, which ensures stability during movement. An anatomo-biomechanical and imaging approach facilitates the understanding of the physiological and pathological aspects of the long finger MCPJ and contributes to improved therapeutic strategies. The aim of this article is to provide a detailed description of the normal anatomy and biomechanics of the MCPJ of the long fingers, correlated with imaging, in order to improve the understanding of physiological and pathological aspects.

Methodology: This educational review presents the normal anatomy and biomechanics of the long finger MCPJ through imaging. The various components of the MCPJ of the long fingers are detailed, including articular surfaces, capsule, collateral ligaments, deep transverse metacarpal ligament, volar plate, dorsal triangular fibrocartilage, dorsal hood, extensor tendons, sagittal bands, and the interosseous and lumbrical muscles. In addition to standard radiography, several imaging modalities are used to evaluate the MCPJ of the long fingers. Dynamic conventional radiography assesses joint stability. Computed tomography (CT) or cone-beam CT (CBCT) can complement the assessment. High-resolution ultrasound (US) is well suited for dynamic studies. High-field 3T magnetic resonance imaging (MRI) provides excellent spatial resolution and contrast.

Results and conclusion: A thorough knowledge of anatomy and biomechanics is essential for the imaging analysis of the MCPJ of the long fingers and forms the basis for exploring both normal and pathological aspects.