The classification of loose bodies in human joints.

A histopathological analysis of 119 surgically excised loose bodies revealed that the cases could be separated into three categories: (1) loose bodies due to synovial osteochondromatosis; (2) loose bodies due to osteochondral fracture; (3) loose bodies due to joint surface disintegration. Three different types of cartilage were identified in the nidus of a loose body--articular, osteophytic, and lobular. Attached bone could be seen from any of the three types of loose bodies but was rare in those specimens secondary to synovial osteochondromatosis. Three mechanisms for the generation of loose bodies in cases of degenerative arthritis or avascular necrosis are proposed: (1) fragmentation of the joint surface; (2) fractured osteophytes; (3) osteochondral nodule proliferation in the pararticular soft tissues. Correlation of the gross and microscopic pathology with the clinical history, roentgenograms and surgical findings usually resulted in a comprehensive understanding of the pathogenesis of any particular case.