Medial sesamoid phalangeal ligament

The medial and lateral sesamoidophalangeal ligaments extend from the same proximal attachments with the main collateral ligaments to the periphery of the sesamoid bone.The SPLs are the thickest first MTPJ ligaments and are the main restraints to proximal sesamoid subluxation when high tensile forces are placed across them during hyperextension (dorsiflexion) on walking or running. As a result, the SPLs are also the most commonly injured when hyperextension occurs.