What is Synovial Chondromatosis?
Synovial chondromatosis (SC) is a rare, non-cancerous (benign) condition that can cause severe discomfort and limit the functioning of the joints. It affects the synovial membrane, a thin layer of tissue that lines the joints, tendons and bursae (small fluid-filled sacs). Although it’s benign and usually doesn’t become cancerous, in some cases, it could potentially convert into a type of bone cancer known as chondrosarcoma. This condition has been recognized for a long time, with the first known documentation of it dating back to 1558.
To diagnose synovial chondromatosis, doctors take a detailed medical history, conduct a physical examination, and use imaging tests such as x-rays on the affected joint. The signs of this condition often include a large buildup of fluid in the joint (effusion) and possible joint deformity due to swelling. Sufferers may experience pain even at rest, and the pain usually increases with movement. Motion of the joint could also be limited. X-rays may show multiple small bone-like (chondroid) fragments in the joint. An MRI scan can provide a more detailed picture of how the condition is affecting the joint and surrounding tissues.
Most commonly, synovial chondromatosis affects only one joint at a time, but in rare cases, multiple joints may be involved. There are two types of synovial chondromatosis: primary and secondary. Each type presents itself differently and requires different treatment approaches. In some rare instances, the condition affects tissues outside the joint (extra-articular), specifically the bursal tissue and the tissue around the tendons close to the affected joint.
What Causes Synovial Chondromatosis?
The cause of the initial form of synovial chondromatosis, a disorder that affects the joints, is still unclear. Doctors have noticed high levels of a protein called “bone morphogenic” found in loose body lesions and the affected joints of patients with this condition. But it’s not sure if this high level actually causes the disease.
In the same way, there are elevated levels of substances called “interleukin-6” and “vascular endothelial growth factor-A” in these joints. Both of these substances are associated with inflammation and blood vessel growth respectively, but we’re still not sure how much of these substances are connected to synovial chondromatosis.
There’s a secondary form of synovial chondromatosis that is believed to happen due to mechanical changes in a joint. These changes happen due to a joint disorder known as ‘arthropathy’. It’s thought that the formation of loose bodies of cartilage is a part of the joint degeneration process that occurs in these patients.
Whether it’s the primary or secondary form, this disease leads to the formation of multiple nodules made of cartilage-like material and loose bodies that are either a mixture of bone and cartilage or purely bone.
Typically, synovial chondromatosis affects a single joint at a time. However, it has been found in as many as 33 different locations within the body. While the condition usually affects the inside of the joints, there have been instances where it affects areas outside of the joints, usually within the tendon sheath, which is the protective covering of the tendons.
Risk Factors and Frequency for Synovial Chondromatosis
Synovial chondromatosis is a condition that affects men about four times more often than women. It usually impacts people who are between 30 and 60 years old. This condition frequently affects the knee, but other joints can be affected as well. The larger the joint and the more weight the joint has to support, the more likely it is to develop synovial chondromatosis. Other areas, like the jaw (temporomandibular) joint, spine facet joints, and multiple tendon sheath locations, might also be affected.
Sometimes, this disease presents as lesions outside of the joints, which is rare but typically occurs in tissue that lines the bursa or tendon sheath in a condition called tenosynovial or bursal chondromatosis. Synovial chondromatosis most frequently occurs in people who are in their fifties, and it’s rare in teenagers or children. There are two forms of the condition; a primary form, which appears without any previous joint pathology, and a secondary form that occurs alongside joint degeneration. The secondary form is the most common and usually affects older people. However, both forms of this disease are rare.
The exact number of cases per year is not known, but in England, it has been reported as being 1.8 per million people per year. There is also a chance of about 10% that the disease could affect both sides of the joint.
Signs and Symptoms of Synovial Chondromatosis
Osteochondromatosis or SC symptoms can be quite vague, and sometimes people may not show any symptoms at all. When symptoms do appear, joint pain is the most common complaint. This pain often comes with swelling and a reduced ability to move the affected joint. Sometimes, people may also feel a grinding sensation in their joints or experience a sensation of their joint being ‘stuck.’
These symptoms most often get worse during physical activity but may even occur when a person is at rest. Issues such as a feeling of instability in the joint, a buildup of fluid around the joint, or problems with the blood vessels or nerves in the surrounding area are reported less frequently.
SC usually affects only one joint (monoarticular) when it happens on its own (primary form) and may impact more than one joint (multi-articular) if related to another condition (secondary form). Recurrence is rare when it occurs on its own but common when it happens alongside another condition such as osteoarthritis, post-traumatic arthritis, or rheumatoid arthritis.
Diagnosis of SC often happens unexpectedly and is frequently delayed; on average, there’s a five-year gap from the time when symptoms first start to when a diagnosis is made.
Testing for Synovial Chondromatosis
If you’re suspected of having a certain type of joint disease, your doctor may rely on special tests to help them diagnose the condition. The type of joint disease they’re looking at is usually primary or secondary, and they can tell the difference between the two based on these tests.
If you have a “primary” type of this disease, which means it’s not caused by another joint condition, your X-Ray, or “radiograph,” will show no other problems with your joint(s). X-rays are basically pictures of the inside of your body, like bones and joints.
The doctor may also order an MRI or a special type of MRI called “MRI arthrography.” An MRI is a type of imaging that uses a large magnet and radio waves to look at structures in your body. In this case, the MRI helps the doctor see any abnormalities in the fluid-filled sac that limits friction in your joints, which is called the “bursal”.
The hip joint is a common place for doctors to find an abnormal bursal. They’ve found it in as many as 71% of people with this disease. In people who might have the “secondary” type of the disease, which means it’s caused by another joint condition, the doctor will try to identify any signs of joint inflammation or arthritis during these tests.
What the doctor is looking for on your X-Rays and MRI scans are small, round areas of hardened tissue, either inside or surrounding your joint. These are a tell-tale sign of the disease they’re looking for, known as synovial chondromatosis.
However, they won’t rely on these tests alone to make a diagnosis. This is because in about 20% of patients, it can take some time for these hardened areas to show up on X-Rays or an MRI. So, even if your joints are painful, you may not see these hardened areas on imaging tests for months or even years. In the meantime, these abnormal tissues can still cause problems in joint or the bursal sac and might even look like a fluid buildup in those areas.
Once the doctor has gotten these test results and come up with a treatment plan, they might want to take more X-Rays regularly. These “serial radiographs” help them keep an eye on whether the disease is coming back or causing new problems in your joint over time.
Other types of imaging tests like Computed Tomography (CT) scan or MRI can be useful in the early stages of the disease before hardened areas might be visible. A CT scan is like an X-Ray, but it makes more detailed images of your body. These tests help the doctor see very subtle changes in the joint surface and the structures around it.
In an MRI scan, the characteristics of these hardened tissues can vary depending on the type of image. Called “T1- weighted” and “T2- weighted” images, they differ based on the settings used to capture the pictures. In T1- weighted images, these hardened areas show up as a low signal but higher than the surrounding muscle tissue. In contrast, T2- weighted images reveal structures with a high-water content like cartilage as a high signal area.
A CT scan, in comparison, is better at identifying areas that have hardened, as these appear as dark or “hypointense” in all types of MRI images.
Treatment Options for Synovial Chondromatosis
Synovial chondromatosis is a condition that can sometimes resolve on its own, so doctors may initially suggest non-invasive treatment methods. These may include various nonsteroidal anti-inflammatory drugs (NSAIDs), altering daily activities to avoid aggravating the condition, and applying cold therapy to the affected area. However, if the condition leads to things like restricted movement or symptoms of locking and catching due to loose bodies (fragments of bone or cartilage floating in the joint), it could lead to severe damage of the joint. Therefore, the best course of action in these cases is often surgery to remove the loose bodies, and possibly the removal of the synovium, a thin membrane inside the joint.
The decision to remove the synovium during surgery is debated amongst medical professionals. Some believe that removing the synovium, which may seem logical given it is the origin of the condition, is beneficial. However, there isn’t strong evidence to support this in addition to the removal of the loose bodies. Some past studies have found no added benefit to removing the synovium. On the other hand, other studies suggest that removing the synovium could prevent the condition from coming back.
Another aspect of the surgery that is debated is whether to go in through a larger, open cut or to use a less-invasive method using special tools and smaller cuts, known as arthroscopy. A larger cut can offer a better view of the joint surfaces, while a less invasive approach may result in quicker recovery, shorter stay in the hospital, less pain after surgery, and faster rehabilitation.
Secondary synovial chondromatosis, which is the condition occurring as a result of another disease in the joint, is typically managed with anti-inflammatory medications. Surgery will usually be indicated only if the joint is no longer functioning well due to mechanical symptoms. The goal of the surgery in such cases would be to improve long-term function and prognosis. This could require joint reconstruction or replacement surgery coupled with the removal of loose bodies.
What else can Synovial Chondromatosis be?
Several health problems can cause the development of loose bodies within the joints or an overgrowth of the synovium, or joint lining. These include:
- Crystal deposition disease (Calcarea tendinosis)
- Osteocartilaginous loose bodies
- Lesions of the bone and cartilage (osteochondritis dissecans)
- Neurotrophic arthritis
- Rheumatoid arthritis
- Arthritis due to wear and tear (degenerative arthritis)
- Tuberculosis of the joints (tuberculous arthritis)
- Fractures involving the bone and cartilage (osteochondral fractures)
- Soft tissue tumors
Other harmless conditions of the joint lining include synovial hemangioma, lipoma arborescent, and pigmented villonodular synovitis (PVNS).
Doctors should also consider that a malignant or cancerous lesion could be the cause. For example, a slow-growing tumor of the cartilage that extends into a joint (low-grade interosseous chondrosarcoma) or a cancer arising from the cells of the synovium (synovial cell sarcoma) can be considered if the lesions are near a joint. MRI scans can help differentiate potential cancerous lesions.
For healthcare providers and pathologists, it can be difficult to tell the difference between synovial chondromatosis and chondrosarcoma. Classic signs of cancer, such as bone invasion, penetration, and destructive growth across joints, often develop late in the progression of the disease. If the condition keeps coming back, especially multiple times, this is a significant sign that warrants consideration of the potential for cancer. However, the number of lesions, their size, or the rate at which they change does not necessarily correlate with cancer.
What to expect with Synovial Chondromatosis
Synovial chondromatosis can sometimes cause damage inside a joint or the surrounding area. That’s why it’s so important to diagnose and treat it quickly, to prevent other health issues from developing. One of the main factors predicting the outcome of the disease is the condition of the cartilage, which is the soft tissue that covers the surfaces of the joint.
It’s rare for synovial chondromatosis to come back after surgery, which involves removing the loose bodies and performing a partial synovectomy, a surgical procedure that removes part of the synovium, a tissue that lines the joints. However, there have been a few cases where the disease has returned in the jaw joint.
Although it’s rare, synovial chondromatosis can sometimes get better on its own, a phenomenon known as spontaneous regression. However, it often takes several years from the time when symptoms first start to the point where they finally go away.
Recovery from Synovial Chondromatosis
After surgery, a part of patient care consists in gradually increasing the range of motion and strengthening the muscles around the joints. Using anti-inflammatory medications that are not steroids post-surgery is not established as beneficial.
