The effect of ultrasonically induced cavitation on articular cartilage.

Cavitation, the term used to describe bubble activity in fluids, is a destructive phenomenon encountered in fluid systems. The effect of cavitation on articular cartilage was investigated by ultrasonically inducing bubble activity on the surface of bovine specimens. Distinctive pits and craters, not present on control specimens, were observed using scanning electron microscopy on the damaged surface. Human osteoarthrotic articular cartilage specimens were removed during arthroplasty and examined using scanning electron microscopy. Craters and pits observed on the osteoarthrotic specimens were similar in appearance to those on the cavitated specimens. The mechanism of cavitation bubble collapse could be responsible for damage in vivo, thus providing articular cartilage with a degenerative pathway toward osteoarthrosis.