Subchondral sclerosis is the hardening of the bone just below the cartilage surface. It shows up in the later stages of osteoarthritis.

Subchondral sclerosis is common in the bones found at the load-bearing joints, such as knees and hips. Other joints can be affected, including the hand, foot, or spine.

When you have subchondral sclerosis, the area just below the cartilage layer fills with collagen and becomes denser than healthy bone. These bones aren’t necessarily stiffer or harder, as was once thought.

The causes of both subchondral sclerosis and osteoarthritis aren’t yet clear. Research is ongoing to figure out if one condition causes the other, or if they’re both symptoms of an underlying condition that isn’t yet understood.

“Chondra” is another word for cartilage, so subchondral means “beneath the cartilage.” “Sclerosis” means hardening.

Your bone tissue is constantly being repaired and replaced, especially in the portion near the joint. When you have subchondral sclerosis, something causes the replaced tissue to become dense and have more collagen than normal bone.

Despite intense study in recent decades, the cause of subchondral sclerosis isn’t yet clearly understood.

Subchondral sclerosis appears in the later stages of osteoarthritis, when there’s a degeneration of cartilage.

For a long time, the sclerosis was thought to be a result of the osteoarthritis. But some recent research suggests that there may be changes in the subchondral bone in the earliest stages of osteoarthritis. It’s thought that these early changes could be a cause, not a result, of the arthritis.

An older view is that as the tip of the bone becomes thicker, it may damage the cartilage in the joint, leading to osteoarthritis.

The risk factors for subchondral sclerosis are the same as those for osteoarthritis. Those most likely to get it include:

  • older adults
  • postmenopausal women
  • those who are overweight or obese

Other factors that make you more likely to get subchondral sclerosis are:

  • joint injuries from sports or an accident
  • repetitive stress on joints
  • misaligned bones, especially at the knee or hip
  • genetics

Subchondral sclerosis usually appears in the later stages of osteoarthritis. It doesn’t give you symptoms separate from those of osteoarthritis.

Osteoarthritis is the wearing away or degeneration of cartilage in a joint. It’s a progressive disease that goes through stages.

As arthritis worsens, the area of the bone just below the cartilage becomes denser. You won’t feel this. It can only be detected by X-ray or MRI.

Subchondral sclerosis may not increase the risk of cartilage loss in your joint. In fact, a 2014 study suggests that it may be protective against cartilage loss and narrowing of the space in your joint.

But subchondral sclerosis may go along with a worsening of the joint pain that comes with arthritis. When you reach this stage, you’ll typically have subchondral sclerosis.

Subchondral bone cysts (SBCs) are another symptom of osteoarthritis. You won’t know if you have these cysts. They first show up on X-rays as tiny fluid-filled sacs just below the surface of the cartilage of the joint.

SBCs aren’t treated separately from your osteoarthritis. Only some people with osteoarthritis get SBCs.

In a study of 806 people with painful knee arthritis, only 31 percent had subchondral cysts. A greater proportion of these were women. By comparison, 88 percent of the same group of people had subchondral sclerosis.

Technically, SBCs aren’t cysts because they don’t have an enclosing layer of cells like other cysts. In later stages, SBCs may harden into the bone and no longer contain fluid.

Other names for SBCs are subchondral lesions and geodes.

Bone spurs

Bone spurs, also known as osteophytes, are another symptom of osteoarthritis in the later stages. There’s no evidence that they’re caused by subchondral sclerosis.

Subchondral sclerosis appears as a region of increased density on an X-ray. If you’re being treated for osteoarthritis in a major joint, your doctor will likely ask for a periodic X-ray of the affected joint as part of follow-up. They may also call for an MRI.

By the time subchondral sclerosis can be seen on an X-ray or MRI, you’re already likely to know that you have osteoarthritis.

Subchondral sclerosis isn’t treated separately, but as part of your treatment for osteoarthritis. Arthritis treatment may include:

NSAIDs

The first-line treatment is usually nonsteroidal anti-inflammatory drugs (NSAIDs). These over-the-counter medications help to reduce inflammation in the joints and include:

  • ibuprofen (Advil, Motrin)
  • aspirin (St. Joseph)
  • naproxen (Aleve, Naprosyn)

Some prescription NSAIDs include:

  • diclofenac (Voltaren)
  • celecoxib (Celebrex)
  • piroxicam (Feldene)
  • indomethacin (Tivorbex)

Physical therapy

Physical therapy focuses on strengthening the muscles around a joint to relieve the strain. For the knee, this involves the thigh and calf muscles. Low-impact exercises such as swimming and biking can also help.

A physical therapist can work out an exercise program for you that matches your level of strength and endurance.

Weight loss

Weight loss can significantly reduce the impact on weight-bearing joints in the knee, hip, and spine. If you’re overweight, taking off extra weight can help relieve pain.

Injections

Two types of injections can be used for people with painful arthritis that doesn’t respond to conservative treatment:

  • Corticosteroids. These injections into the affected joint can sometimes provide relief. The effect lasts only a month or two. Corticosteroids aren’t recommended for continuous treatment because of their side effects.
  • Viscosupplements, such as Synvisc. These are injections of hyaluronic acid into your joint. Hyaluronic acid is a part of the natural lubricant, called synovial fluid, that surrounds your joints.

Surgery

Surgery is a last resort when all other treatments fail. Hip and knee replacement surgery are now common. But surgery comes with the risks of side effects and failure to relieve the pain.

Subchondral sclerosis is a change in your bone tissue that occurs in the later stages of osteoarthritis. It’s something your doctor will recognize on an X-ray or MRI while monitoring the progression of your osteoarthritis. It’s not treated separately from arthritis.

Osteoarthritis is a very common condition, especially as we age or have joint injuries. It involves the loss or degeneration of the cartilage in our joints.

Despite decades of intense research, the causes of this common condition aren’t yet clearly understood. Treatments including NSAIDs, physical therapy, weight loss, and low-impact exercise can go a long way toward relieving symptoms.

Stronger pain medications are sometimes needed. Joint replacement surgery is a last resort. If you’re experiencing pain as a result of osteoarthritis, talk to your doctor about the best approach.