What Is Subchondral Sclerosis?

Doctor pointing at hip joint. Credit: Jan-Otto / Getty Images

Subchondral sclerosis is commonly seen on X-rays of joints affected by osteoarthritis. You may see the term used in a radiology report in your medical record or you may run into the term when you are reading about the causes and symptoms of osteoarthritis or in research papers on the condition. What does it mean?

Subchondral Sclerosis in Osteoarthritis

When you have an X-ray done to diagnose osteoarthritis, subchondral sclerosis is one of the things the radiologist is looking for.

It shows up on X-ray as a denser area of bone just under the cartilage in your joint. It is more likely to be seen in late stages of osteoarthritis.

Subchondral bone is the layer of bone just below the cartilage in a joint. With osteoarthritis, there is increased blood flow and other changes that develop in the subchondral layer of the joint. These include subchondral sclerosis, the formation of subchondral cysts,  and increased pressure within the bone. All of these are thought to contribute to osteoarthritis pain in the joint. The joint pain is probably what brought you to the doctor and resulted in having the X-ray to look for these signs of osteoarthritis.

Subchondral bone sclerosis seen with progressive cartilage degradation is considered to be a hallmark of osteoarthritis, a clear sign of the presence of the condition in the joint. It is most commonly seen in late-stage osteoarthritis.

Subchondral sclerosis is defined as increased bone density or thickening in the subchondral layer of a joint. This often occurs with progressive osteoarthritis and shows up on x-rays as abnormally white (dense) bone along the joint line. Subchondral sclerosis is seen in osteoarthritis in many of the commonly affected joints.

These include the knee, hip, spine, and foot. 

Subchondral sclerosis can also be seen in calcium pyrophosphate deposition disease, previously known as pseudogout. The x-ray findings for CPPD are similar to osteoarthritis, with joint space narrowing and extensive subchondral sclerosis.

Is Subchondral Sclerosis a Bad Sign for Osteoarthritis Progression?

Studies do not show that subchondral sclerosis predicts how osteoarthritis of the knee will progress. While it is a hallmark of the presence of the condition, it is of less value in determining what will happen next in the joint.

A study in 2014 looked at whether subchondral sclerosis as detected by MRI was associated with loss of cartilage. They enlisted 163 people with knee pain and followed them for three years with baseline knee x-rays and MRI examinations. They found no significant associations between baseline subchondral sclerosis and increased risk of cartilage loss in the same region of the knee.

Another study published in 2014 questioned whether subchondral sclerosis was actually protecting the knee from joint space narrowing in patients with varus knee osteoarthritis.

They looked at 192 women who had already been diagnosed with varus knee osteoarthritis and conducted knee radiograph, dual-energy x-ray absorptiometry at the lumbar spine, proximal femur, and knee condyles. They concluded that the increase in subchondral bone sclerosis in medial femoral and tibial condyles might protect the decrease of cartilage thickness.

Sources:

Radiographic Assessment of Osteoarthritis. American Family Physician. Swagerty DL et al. July 15, 2001.
http://www.aafp.org/afp/2001/0715/p279.html

Y. Akamatsu, H. Kobayashi, Y. Kusayama, K. Kumagai, N. Mitsugi, T. Saito. "Does Subchondral Sclerosis Protect Progression of Joint Space Narrowing in Patients with Varus Knee Osteoarthritis?" Osteoarthritis and Cartilage 22 (2014) S57–S489

Crema MD, Cibere J, et. al. "The relationship between subchondral sclerosis detected with MRI and cartilage loss in a cohort of subjects with knee pain: the knee osteoarthritis progression (KOAP) study." Osteoarthritis Cartilage. 2014 Apr;22(4):540-6.

Guangyi Li, et.al. "Subchondral bone in osteoarthritis: insight into risk factors and microstructural changes" Arthritis Res Ther. 2013; 15(6): 223.

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