A subchondral fracture is a type of injury that occurs due to repetitive stress in the layer of bone tissue just beneath the cartilage. It often happens to the knees or hips of older adults.

Subchondral fractures are nontraumatic, which means they’re not caused by a fall, a hit, or any traumatic event. Instead, they occur due to repetitive loading over time.

They are also called subchondral insufficiency fractures. “Insufficiency” refers to a type of stress injury that typically occurs in weight-bearing joints like the knees and hips.

Low bone density can make you more vulnerable to these fractures, though it’s not the underlying cause.

Here’s what to know about their causes, types, and treatments.

There are two main types of subchondral fractures. One occurs in the knee, and the other occurs in the hip. However, you can also experience symptoms in other parts of your body.

Knee subchondral fracture

Subchondral insufficiency fractures of the knee (SIFK) happen due to repetitive stress to the tissue beneath the cartilage in the knee. These are common causes of joint pain in middle-aged and older adults.

Hip subchondral fracture

Subchondral insufficiency fracture of the femoral head happens because of repetitive stress on the hip joints. The femoral head is the ball that attaches the upper end of the femur (thighbone) to the pelvic bone.

Like subchondral knee fractures, these tend to happen to older adults.

People typically first notice subchondral fractures due to severe pain felt in the area of the bone. Most of the time, there won’t be any obvious cause. But you will likely be able to remember when the pain first began.

Though these fractures often occur in the hips or knees, they can also occur in the ankles, wrists, shoulders, elbows, or other joints. Your joints will feel swollen due to fluid buildup in the joint.

The pain tends to get worse when lifting objects. It will persist even when resting, including at night. The pain will also tend to worsen over time, especially without treatment.

Since the pain tends to be one-sided, you might feel it in just one hip or knee. But you could also feel it in both.

Subchondral fractures occur due to repetitive stress, and there generally won’t be any obvious cause. Walking, running, or doing everyday tasks over time could be enough to cause microfractures in the bone.

Though low bone density or osteoporosis may make a subchondral fracture more likely to occur, it’s not the underlying cause.

Subchondral fracture risk factors

Subchondral injuries of the knees and hips are more likely to occur in people ages 50 and above, particularly women.

Women are also more prone to bone density loss and osteoporosis over time, which is another risk factor for bone injury, including fractures.

Those who engage in repetitive motion activities like heavy lifting or running may more likely develop subchondral fractures.

Diagnosis of subchondral fractures can be made in their earliest stages by MRI. However, your doctor will likely start by ordering an X-ray.

If the X-ray comes back inconclusive and you are still experiencing persistent pain, the doctor will order an MRI. The MRI will easily be able to detect a subchondral fracture.

Though subchondral fractures can be challenging to detect with other types of diagnostic imaging, the doctor should be able to see subtle bands in the tissue that are irregular and disconnected.

Sometimes, bone marrow edema (when fluid builds up in the soft tissue) and bone collapse may be visible too.

Radiographs of subchondral fractures typically don’t reveal any abnormalities and therefore aren’t recommended. For this reason, when an older adult with the condition experiences sudden-onset pain in the joint, the doctor might recommend an MRI.

In most cases, doctors recommend noninvasive management as the first course of treatment. Protected weight-bearing is usually the first step, meaning that you should only bear weight with the support of gait aids (like crutches) for a period of time. Other measures may also be employed, including:

Experts are exploring procedures such as decompressing the hip and using bone filler to restore the joint. However, extensive research is necessary before implementing measures like these on a broader scale. Another potential alternative is cooled radiofrequency ablation for pain relief combined with bone infusions to address the weakened bone.

Physical therapy, vitamin D administration, and several other experimental measures are useful in treating the condition.

More serious intervention may be necessary if the issue persists for more than 3–8 months.

For instance, in the case of a severe fracture of the femoral head, total hip arthroplasty may be the next required step. This kind of surgery involves replacing the joint between the femur and pelvis with an implant. In an advanced SIFK case, a knee replacement may be necessary.

Since advanced subchondral fractures can be notoriously challenging to treat, there’s a lack of consensus among doctors about how to best manage them. So ultimately, it’s up to you and your doctor to find the best course of treatment.

How long does a subchondral fracture take to heal?

Since treatment can vary widely, how long a subchondral fracture takes to heal can vary.

In a small 2007 study, conservative management (involving steps like protected weight-bearing, insole therapy, anti-inflammatory drugs, and bisphosphonates) led to healing in people with the condition within an average of 4.8 months. Within about 8 months, the study participants’ MRIs returned to baseline.

In the case of surgical intervention such as total joint replacement, the healing process may take much longer. The larger the lesion size, the more challenging the condition can be to treat and heal. For this reason, the lesion may be difficult to heal in some people. In general, total joint replacement is considered a last resort.

If the bone tissue doesn’t heal naturally or via medical intervention, it can turn into osteonecrosis and osteochondral collapse, which is the death of the joint.

It happens when there is a disruption of blood supply to the knee. Since bone cells need regular blood flow to survive, osteonecrosis can lead to total joint destruction and severe arthritis.

Experts are continuing to develop more effective strategies to heal these fractures. Due to potential complications, early diagnosis and management are key.

Subchondral fractures involve the breakdown of the tissue below the cartilage in a joint. They tend to occur in older adults due to repetitive movement over time.

In mild cases, noninvasive methods like protected weight-bearing and anti-inflammatory drugs help treat the condition. In more severe cases, surgical intervention (including hip or knee replacement) may be necessary.

If you’ve experienced sudden-onset pain in a joint like your hip, knee, or shoulder, speak with your doctor. The earlier the diagnosis of the condition and treatment, the better the outlook.