Determining the amount of space between the bones in a person's joints is a tool that doctors use when evaluating arthritis. When the space starts to narrow, it may be an early indication that someone has an arthritic condition.

Joint space narrowing (JSN) is also a starting point for deciding the type of treatment to give for arthritis.

When joints are healthy, they show normal spacing where the bone ends meet. The bone ends are covered by white tissue called articular cartilage, which covers the place where bones come together to form the joints.

The goal in treating arthritis is to prevent further damage to joints and any worsening of the accompanying pain and lack of mobility.

Fast facts on JSN:

  • JSN results from overuse of joints and aging as joints experience wear and tear over time.
  • A 2015 study in the medical journal Osteoarthritis and Cartilage, found that JSN and knee pain were connected.
  • Surgery may be necessary to restore mobility and replace joints that are damaged and causing disability.

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Cartilage works as a cushion and shock absorber for bones.

Healthy cartilage makes it easier for joints to move and allows bones to glide over one another without friction, acting as both cushion and shock absorber.

But articular cartilage between the bones in a joint can become damaged by injury or simple wear and tear.

If joints are affected by arthritis and articular cartilage is damaged or worn away, X-rays will show evidence of JSN between the bone ends. Joints affected by JSN can become stiff, painful, and see their range of motion reduced.

As the protective cartilage further wears away and spacing worsens, bone starts rubbing on bone. Bones must now compensate for the spacing, and so they start to grow outward, forming bone spurs.

Being overweight and having muscle weakness contributes to JSN. Osteoarthritis (OA) and rheumatoid arthritis (RA) are other contributing factors to JSN.

OA affects 30 million American adults, according to the Centers for Disease Control and Prevention.

JSN is more often seen in older adults, even those with early stage OA. Moreover, it appears that some women may have JSN that precedes early OA, according to researchers from Brown University, Rhode Island.

X-rays can show how much space there might be between a thighbone, lower leg, knee, or other joint. But there is more to JSN than simply determining the spacing in a person's joint.

JSN is a starting point

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Knees may be susceptible to JSN.
Image credit: James Heilman, MD, 2010

The evaluation of arthritis involves determining if JSN has occurred and, if so, by how much. Hips and knees are the most susceptible to JSN.

For people with OS, their joint spacing is generally asymmetrical, which means that both sides are not equally affected. In other words, severe JSN and bone-on-bone rubbing affecting one hip, does not mean the other side is necessarily affected to an equal extent.

The only time JSN is symmetric is when it is located in the finger joints. JSN in the finger joints has been associated with both OA and RA.

One 2012 report in Arthritis Research & Therapy looked at JSN in the finger joints, using two types of magnetic resonance imaging (MRI). MRI has been shown to be more accurate in detecting bone erosion, synovitis or inflammation of joint lining, and osteitis or inflammation of bone in cases of RA.

A further study, reported in the Annals of the Rheumatic Diseases, looked for connections between deterioration on ultrasound and conventional X-ray in people with OA of the hands. Of the 1649 joints among the 55 participants, 47 percent had JSN associated with OA of the hand.

JSN indicates worsening arthritis

The wear and tear from OA eventually results in loss of cartilage and joint deterioration. When doctors want to determine how severe OA is, they measure the space between the bones in the joint. The less space there is, the worse is the OA in that joint.

JSN in OA treatment

A surgical technique called arthroscopy was used in the past to treat osteoarthritis, but it is no longer indicated, as studies have shown it not to be beneficial.

Scoring

JSN is measured using a system called the Kellgren-Lawrence grading scale, which was established in 1957.

The scale is based on five grades of measurement, starting with no OA radiographic features (grade 0), and ending at grade 4 where OA has caused large bony spurs plus notable JSN, severe bone deformity and severe sclerosis or hardening of bony structures.

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Pain may be the first symptom of JSN, as the cartilage deteriorates.

Pain is normally a symptom after a person's joint cartilage has started to wear away. And the pain worsens as more cartilage deteriorates, and bone starts rubbing against bone.

The joints most affected by this wearing down are the knees, hips and hands, but any joint can be compromised.

The more of the cartilage that is lost in the joints, the harder it is for a person to move and manage everyday tasks.

Treatment for arthritis aims to stop the condition from worsening and will vary, depending on the type of arthritis a person is experiencing.

For example, RA treatment requires the use of disease-modifying antirheumatic drugs (DMARDs) and biologics, to stop inflammation caused by the immune system, which, in turn, is damaging the joints

On the other hand, OA treatment involves drugs that reduce the pain and the swelling caused by the condition, and lifestyle changes to help protect the joints.

JSN can be halted if these treatment methods are successful and recommendations for various lifestyle changes are followed.

JSN results from arthritic conditions that include RA and OA. As soon as a person starts to experience pain, swelling, and stiffness, they should see a doctor to have X-rays and tests done. Based on the results, treatment and lifestyle changes will probably be recommended to halt joint damage and slow further JSN.

Arthritis is a common condition that worsens with age and without proper treatment and management.

JSN can be treated and halted, resulting in improved quality of life. A person should work with their doctor to find a treatment plan that works best for their situation.