Osteoarthritis (OA), the most common form of arthritis and the leading cause of disability in the elderly, causes structural deterioration of joints. It is common for physicians to quantify this deterioration by measuring the amount of space between the different components of the joint. A narrowing of the joint space indicates worsening osteoarthritis.
What problem was studied?
Loss of joint space within the knee has been equated with loss of articular cartilage. However, previous studies indicate that meniscal disease (menisci are wedges of tissue between the cartilage surfaces that distribute weight and improve joint stability) is also an important contributor of joint space narrowing. Lead researcher David J. Hunter, MD, PhD, of Boston University School of Medicine (along with Arthritis Foundation-funded researchers Shreyasee Amin, MDCM, MPH, of Mayo College of Medicine in Rochester, MN, and David T. Felson, MD, MPH, of Boston University School of Medicine, as well as others from Synarc in San Francisco, and the VA Medical Center in Boston) examined the relative contributions of cartilage loss, position of the meniscus and meniscal degeneration to changes in joint space to determine whether it is changes in articular cartilage or changes in meniscus that lead to joint space narrowing.
What was done in the study?
Magnetic resonance images (MRI) of the knees of 264 people with symptomatic knee OA were taken at the beginning of the study, after 15 months and after 30 months. Meniscal degeneration, cartilage changes and position of the meniscus within the joint were assessed. X-rays of the knees also were taken and joint space narrowing was graded on a 0 (normal ) to 3 (bone on bone) scale.
What were the results?
In knees with a joint space narrowing score greater than zero, cartilage changes and meniscal position abnormalities were almost universal. The authors conclude that “a large contribution to the variance in joint space narrowing is explained by alterations in the meniscus.” They go on to say that structural changes that come with OA go together: as the articular cartilage becomes abnormal, the meniscus degenerates and becomes displaced. Narrowing of the joint space reflects changes in all of these structures.
What does this mean to people with autoimmune disease?
The results of this study have important implications for how scientists and physicians test the efficacy of OA treatments. Currently, researchers decide if structure-modifying OA agents are working by measuring the joint space on plain X-rays. However, if the agent is supposed to be working on cartilage, scoring the joint space may not be the best measure because the narrowing may reflect meniscal changes. Scientists will need to measure the cartilage itself, not just the joint space, to determine how well a treatment is working.