Medical records from 119 horses that had undergone arthroscopic surgery for removal of axial osteochondral fragments of the palmar/plantar proximal aspect of the proximal phalanx were reviewed. Standardbred racehorses represented 109 (92%) of those affected. Ninety-three (78%) of the horses were < 3 years old. Gender distribution was consistent with that of the equine hospital population. Fragments most commonly were observed in the hind limbs (155/164; 95%), specifically, on the medial aspect of the left hind limb (72/164; 44%). Bilateral fragmentation occurred in 21 of 119 (18%) horses, and 15 of 119 (13%) horses had fragments in the medial and lateral aspect within the same joint. Fifteen (13%) horses had a concurrent osteochondritis dissecans lesion on the distal intermediate ridge of the tibia, and 30 of 119 (25%) had radiographic signs of osteoarthritis involving the centrodistal (distal intertarsal) and tarsometatarsal articulations. In 55 of 87 (63%) racehorses and in 100% of the 9 nonracehorses, performance returned to preoperative levels after surgery. Fragment numbers or distribution, concurrent osteochondritis dissecans lesions of the distal intermediate ridge of the tibia, or tarsal osteoarthritis were not significantly associated with outcome. Abnormal surgical findings, consisting of articular cartilage fibrillation or synovial proliferation, were significantly (P < 0.0001) associated with adverse outcome; these findings were documented in 31% of the 32 horses without successful outcome and in only 2% of the 55 horses with successful outcomes.