MR imaging of the metacarpophalangeal joints.

The metacarpophalangeal joint complex represents an articulation not only between the metacarpal and proximal phalanx but in the case of the thumb also between the metacarpal and sesamoids. The collateral ligaments and volar plate contribute significantly to the stability of the metacarpophalangeal joints. Detailed knowledge of the anatomy of the articulations and soft-tissue supports of this complex is necessary for MR imaging detection of subtle injuries to these structures. The role of MR imaging in both acute and chronic trauma to the collateral ligaments and in the often difficult diagnosis of chronic thumb sesamoiditis is presented, with illustrative examples of the normal and pathologic conditions of metacarpophalangeal joints.