The objective of this article is to review data on joint distraction used to treat knee osteoarthritis. Joint distraction is a surgical procedure in which the two bony ends of the joint are gradually pulled apart then kept separated for 2 months in an external fixation frame. Weight bearing is continued to ensure variations in hydrostatic pressure within the joint. In published studies, joint distraction provided substantial clinical and structural improvements in patients with knee osteoarthritis, delaying joint replacement surgery for at least 2 years. Animal studies showed that joint distraction was associated with decrease in the secondary inflammatory response, cartilage breakdown, and subchondral bone remodeling. In vitro, the intermittent application of hydrostatic pressure stimulated the production of extracellular matrix, particularly in joints with osteoarthritis. Nevertheless, several considerations invite caution when considering the more widespread use of joint distraction. Published studies have short follow-ups and small sample sizes. In addition, the high frequency of pin tract infection is of concern, since most patients eventually require knee replacement surgery. These two considerations indicate a need for longer-term prospective studies of patient cohorts.