What Is Joint Space Narrowing?

Measuring the Progression of Osteoarthritis

X-ray images can detect joint space narrowing. In a healthy joint, there is a normal amount of space between the ends of the bones that form the joint. The ends of the bones in a joint are covered by articular cartilage. In an unhealthy joint—one that is affected by arthritis—there is evidence of narrowing of the space between the ends of the bones in the joint, due to cartilage loss.

Joint space narrowing evident on knee x-ray
BSIP / UIG / Getty Images

The articular cartilage serves as the cushion and shock absorber within the joint. When cartilage deteriorates or wears away, the affected joint becomes painful, stiff, and limited in its range of motion. When a joint is severely damaged and cartilage is totally worn away, the damage is commonly referred to as bone-on-bone.

Joint Space Narrowing in Arthritis Diagnosis

Evaluating arthritis usually involves measuring the joint space and judging whether it has narrowed. A weight-bearing X-ray is taken to look for joint space narrowing in the hips and knees.

In osteoarthritis, the joint space narrowing is usually asymmetric. It varies in the different knee compartments of the same knee and surfaces of the hip joint affected. However, it is usually symmetric in osteoarthritis of the joints in the hand.

While joint space narrowing is often the first step during arthritis diagnosis, it is just an indication. Joint space narrowing has a different meaning and shows up at different times in various types of arthritis. The width of the joint naturally decreases with increasing age beginning in early adulthood, and this effect is enhanced by osteoarthritis.

Other radiographic findings, as well as results of a physical examination and blood tests, must also be considered during the diagnostic process. Joint space narrowing may occur with various rheumatic conditions, including osteoarthritis, rheumatoid arthritis, inflammatory arthritis, erosive osteoarthritis, gout, or systemic lupus erythematosus.

An Indication of Worsening Osteoarthritis

The wear and tear of osteoarthritis is characterized by joint deterioration and a 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.

A study tracked cartilage damage and meniscal worsening for 30 months in 276 subjects (one knee/subject) and found that although worsening of cartilage damage was more common than meniscal damage, each independently predicted an increase in joint space narrowing.

Grading Severity

The severity of osteoarthritis is graded using a system called the Kelligren-Lawrence grading scale, which was first proposed in 1957. It measures the progression of osteoarthritis in the joints on a five-point scale.

Kellgren-Lawrence Grading Scale

  • 0: No signs of change
  • 1: A "doubtful" change in joint space narrowing
  • 2: Minimal change that is primarily characterized by osteophytes
  • 3: Moderate change with multiple osteophytes and/or definitive joint space narrowing
  • 4: Severe change with considerable joint space narrowing, bone-on-bone contact, and significant osteophytes

This system remains in use and is based on weight-bearing X-rays. Weight-bearing X-rays may be used to grade in a clinical setting and to predict disease progression. Some have called the evaluation of joint space narrowing as "time to joint replacement," but that does not take into account the many other factors that go into a decision regarding a joint replacement.

A Word From Verywell

There are no medications that impact osteoarthritis progression at this time. The development of DMOADS (disease-modifying osteoarthritis drugs) has been disappointing, to say the least.

Part of the problem, if we choose to call it a problem, in developing drugs that would slow down the progression of joint space narrowing is that the cause of osteoarthritis is more complicated than simple wear and tear. There are proinflammatory factors and proteases involved in joint tissue destruction associated with osteoarthritis. That said, without effective treatment to slow osteoarthritis progression, the significance of grading and scoring joint space narrowing is somewhat limited.

Most osteoarthritis treatments are aimed at managing symptoms, and they are the best options available for reducing pain and enhancing your quality of life.

Frequently Asked Questions

  • How is joint space narrowing tested?

    In most cases, doctors look for joint space narrowing with X-rays (radiography). Other methods of imaging, such as MRI and ultrasound, may also be used to detect certain types of arthritis, including rheumatoid arthritis.

  • What causes patellofemoral joint space narrowing?

    Patellofemoral joint space narrowing is caused by patellofemoral arthritis, a condition that can wear down the articular cartilage on the underside of the patella (kneecap). The articular cartilage protects the patella and helps it glide freely over the knee joint. Without the cartilage, the underside of the patella becomes inflamed and the bone can be exposed, causing pain.

13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Carol Eustice
Carol Eustice is a writer who covers arthritis and chronic illness. She is the author of "The Everything Health Guide to Arthritis."