What Is a Subchondral Bone Cyst?

Ganglion cysts in the wrist. Credit: Biophoto Associates / Getty Images

What Is a Subchondral Bone Cyst?

A subchondral bone cyst is a fluid-filled sac that forms inside of and extends from the bone of a joint. It is seen on X-rays in cases of osteoarthritis. These cysts are not treated. They are a sign of osteoarthritis, although they do not occur in all cases.

Osteoarthritis is caused by the breakdown of cartilage in one or more of your joints. Cartilage serves as a cushion between the bones of your joints, allowing the bones to glide over one another and absorb the shock from your physical movements.

Osteoarthritis progresses in stages. Here is the typical pattern that you can expect to see in a joint with osteoarthritis:

1 - Joint space begins to narrow and osteophytes form
2 - Joint space disappears as cartilage wears away and bone rubs on bone
3 - Subchondral cysts appear within and extending from the bone underlying the joint space.
4 - Bone tries to repair itself and there is bone remodeling.

What is a subchondral cyst? What is the recommended treatment for a subchondral cyst?

Formation of Subchondral Bone Cysts in Osteoarthritis

Subchondral cyst formation is characteristic of osteoarthritis and can be routinely found on x-rays. A subchondral cyst is a fluid-filled sac that extrudes from the joint, consisting of thickened joint material (mostly hyaluronic acid, a substance found in the normal joint fluid that serves to lubricate the joint).

Subchondral bone is the layer of bone just below the cartilage.

When someone has osteoarthritis, there is increased blood flow and other changes that develop in the subchondral layer -- subchondral sclerosis (increased bone density), subchondral cyst formation and increased pressure within the bone -- all of which may cause osteoarthritis pain.

Significance of Subchondral Bone Cysts

A subchondral cyst formation is indicative of an early phase of osteoarthritis.

It is often the case that the subchondral cyst improves without medical attention, although the disease itself does not go away.

The subchondral bone cysts may have a destructive role in osteoarthritis progression. When they intrude into the subchondral plate and calcified cartilage, they can cause more destructive processes in the bone and cartilage.

While subchondral bone cysts are considered a cardinal radiological finding for knee osteoarthritis, a study of 806 patients with knee osteoarthritis found them in only 30.6% of the cases, more often in females. Meanwhile, the other characteristics were far more common, with 99.5% showing narrowed joint space, 98.1% osteophytes, and 88.3% subchondral sclerosis.

Treatment for Subchondral Cysts

If the subchondral cyst causes discomfort, Nonsteroidal anti-inflammatory drugs (NSAIDs) may provide relief. It may also be recommended that you try to avoid activities that irritate the joint that is involved with osteoarthritis. Lower-impact activities would be better than higher-impact activities for knees and hips.

The recommended treatment for a subchondral cyst is to just leave it alone. A subchondral cyst should not be lanced or removed, especially because removal would cause an increased risk of infection or possible problems with wound healing. Instead, symptom relief, lifestyle modification and eventual joint replacement are the usual courses of treatment.


Radiographic Assessment of Osteoarthritis. Swagerty DL. et al. American Family Physician. July 15, 2001.

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

Han Xinyun Audrey, Hamid Rahmatullah Bin Abd Razak,* and Tan Hwee Chye Andrew. "The Truth Behind Subchondral Cysts in Osteoarthritis of the Knee." Open Orthop J. 2014; 8: 7–10.

What are subchondral cysts and how are they treated? Doyt Conn, MD. Arthritis Today. Accessed 5/26/2008.

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