We report the cases of 2 young-adult patients with multiple loose bodies, one in the knee and the other in the elbow joint. Loose bodies were composed of hundreds of brilliant white particles up to 5 mm in the first patient, who had a history of pain and swelling. From the right elbow joint of the second patient, arthroscopic removal of about 25 osteocartilaginous loose bodies, ranging from 5 to 14 nun in diameter, was performed. This patient also had the effects of poliomyelitis, which had required him to use a crutch since childhood for right lower limb length discrepancy. Arthroscopic removal provided elimination of symptoms in both patients. Histopathologic examination of the specimens and clinical evidence supported the previously proposed pathogenic mechanisms on development of loose bodies. Mechanisms that could affect the natural history of loose bodies in these particular patients are discussed and speculated on in this report. We suggest that some of the numerous cartilaginous multiple loose bodies in the joints (snowstorm appearance) are attached and incorporated into synovium, and the total number decreases with time, while the remaining grow with nutritional effects of synovial fluid medium, resulting in larger loose bodies with osteocartilaginous characteristics. The term "hailstone" is used to describe the ultimate situation of the previous arthroscopically defined snowstorm loose bodies.