Natural history of knee cartilage defects: improvement as well as deterioration

A Tasmanian study has identified a high rate of knee cartilage defects in otherwise healthy middle-aged volunteers and considerable variation in the defects - both improvement and deterioration - during two years of follow-up.The 325 participants had a mean age of 45 years. Half were the children of patients who had knee replacement surgery for osteoarthritis, and the remainder were recruited randomly from electoral rolls. T1-weighted fat-saturated MRI was performed at baseline and two years later.Radiographic osteoarthritis of the knee was uncommon, identified in only 17%, but virtually all participants had cartilage defects evident on MRI. In 33% the defects worsened during follow-up, defined by an increase of one point or more in a 0-4 grading scale. The defects improved in 37% and were stable in 30%. A grade 1 defect consisted of focal blistering and intracartilaginous low-signal intensity area with an intact surface and bottom. A grade 4 defect consisted of full-thickness chondral wear with exposure of subchondral bone.A worsening in the cartilage defect score was associated with being female, older and more overweight, having tibiofemoral osteophytes, having a higher tibial bone area and higher cartilage volume. The associations suggested these factors were involved in the pathogenesis of cartilage defects, some already being recognised as risk factors for knee osteoarthritis, and that they might prove useful targets for preventive interventions. For example, participants who lost weight during the study had a significant improvement in the cartilage defect score.Knee cartilage defects were commonly found on MRI in healthy subjects and by arthroscopy in patients with knee symptoms, in whom they were thought to be a result of trauma, but little had been known about their natural history. Defects led to osteoarthritis in surgical models in rabbits, but there were few human data to support the hypothesis.The Tasmanian study, conducted at the Menzies Research Institute, was thought to be the largest ever conducted on the topic.Reference...