Hallux osteochondritis dissecans is a sports-related injury that is likely caused by hyperflexion or hyperextension of the interphalangeal (or metatarsophalangeal) joint. If the avascular fragment turns into a loose body, it must be removed surgically 1.
Also visible on the images is a so-called cleft epiphysis at the base of the proximal phalanx. This is a normal variant and must not be taken for a fracture.