In healthy joints, articular cartilage serves as the cushion within the joint, and as a shock absorber. When cartilage deteriorates or wears away, the affected joint becomes painful, stiff, and limited in its range of motion. X-rays often reveal joint space narrowing. What does this mean? Is it an important aspect of osteoarthritis?
Joint Space Narrowing Means Osteoarthritis is Getting Worse
Osteoarthritis is characterized by joint deterioration and loss of cartilage. When doctors assess the severity of osteoarthritis, they use imaging studies to quantify joint damage by measuring the space that exists between the bones of a joint. Narrowing joint space indicates cartilage loss and worsening osteoarthritis.
Joint Space Narrowing in the Knee
In the knee, joint space narrowing has been linked to loss of articular cartilage. However, meniscal damage also contributes to joint space narrowing.
In one study, MRIs of the knees of 264 study participants with symptomatic osteoarthritis were taken at the start of the study, after 15 months, and after 30 months. Researchers concluded that alterations in the meniscus (knee cartilage) accounted for changes to joint space narrowing. Researchers explained that with osteoarthritis, as articular cartilage becomes abnormal, the meniscus is damaged and displaced. Joint space narrowing is the consequence of changes to all of these structures.
'Scoring' Joint Space Narrowing
According to Medscape, "The global system of Kellgren and Lawrence, developed for use in epidemiologic studies, comprises a 5-point scale for grading radiographs of osteoarthritic joints, in which 0 = no changes; 1 = doubtful joint space narrowing; 2 = minimal change, mostly characterized by osteophytes; 3 = moderate change, characterized by multiple osteophytes and/or definite joint space narrowing; and 4 = severe change, characterized by marked joint space narrowing with bone-on-bone contact with large osteophytes." This system is still used and is based on non-weight bearing x-rays. Weight bearing x-rays are currently used to grade in the clinical setting.
Sources:
Joint Space Narrowing: Cartilage Loss or Meniscus Position? Arthritis Foundation. Accessed 11/26/2007.
<http://www.arthritis.org/joint-space-narrowing.php>
Management of Osteoarthritis Knee Pain: The State of the Science;Council for Osteoarthritis Pain Management, Medscape. Release Date: June 27, 2006;
<http://www.medscape.com/viewprogram/5602>
