Linda Crampton is a writer and teacher with a first-class honors degree in biology. She often writes about the scientific basis of disease.
The Synovium and Synovitis
The synovium is a membrane that lines the inside of many of our joints. It secretes a lubricating fluid that helps a joint to function properly. Unfortunately, it sometimes become inflamed, resulting in a painful condition called synovitis. Synovitis often occurs as a symptom of rheumatoid arthritis, lupus, or gout. It may also be present due to an infection or an injury in the joint.
For a long time, it was thought that no inflammation—and therefore no synovitis—was present in the joints of someone suffering from osteoarthritis. Now researchers are discovering that inflammation is involved in at least some cases of osteoarthritis and that synovitis may be present.
Ligaments joins bones together at a joint. A tendon attaches a muscle to a bone. A bursa is a sac that is lined by synovial membrane and filled with fluid. It acts as a cushion between a bone and a tendon or a muscle.
What Is a Synovial Joint?
A joint in the human body is a region where one bone ends and another begins. The most common type of joint in our body is called a synovial joint. In this type of joint, there is a small space between the ends of the bones. The space is known as the synovial cavity. The surfaces of the bones are covered with a thin layer of articular cartilage and the joint is surrounded by a capsule. The inner lining of this capsule is the synovium, or the synovial membrane. (It’s referred to as the synovial lining in the illustration above.) Synovial joints are present in the limbs, shoulders, and hips and between the first and second cervical vertebrae in the neck.
Functions of the Synovium
The synovium secretes a lubricating fluid into the space between the bones. This fluid is known as synovial fluid. The fluid and the articular cartilage work together to reduce friction, absorb shock, and ensure that the bones move smoothly over each other as a person moves his or her body.
Synovial fluid is clear, colorless, and thick. It resembles uncooked egg white in appearance. The fluid's name is derived from "ovum", the Latin word for egg. It contains water, enzymes, and other substances, including hyaluronate (or hyaluronic acid) and a protein called lubricin. Hyaluronate and lubricin work together to lubricate the surfaces of the bones. Synovial fluid also transfers nutrients from the blood to the articular cartilage.
In synovitis, the synovium is irritated by a trigger of some kind and becomes inflamed. During this inflammation, the synovium becomes thickened and filled with fluid. Some of the fluid escapes into the joint capsule. This makes the joint swollen and painful, which in turn makes movement of the joint difficult.
Unfortunately, a cascade of damaging events takes place when the synovium is irritated. In this cascade, there is an increased blood flow to the joint, which may make the area feel warm. White blood cells leave the blood and enter the joint capsule. Here they release inflammatory chemicals. As a result, the articular cartilage may be damaged.
Temporary inflammation is generally beneficial because it helps an injury to heal. Chronic or excessive inflammation can be harmful and can damage body structures.
Pathological Processes in Synovitis
Rheumatoid Arthritis, Lupus, and Gout
Synovitis is a major component of several diseases, including rheumatoid arthritis, lupus, and gout.
Rheumatoid arthritis is an autoimmune and inflammatory condition in which a person's immune system mistakenly attacks the synovium of the joints. The synovium becomes inflamed and the joint becomes swollen, painful, and stiff. Eventually, the joint may be damaged by the inflammation. Other areas of the body may also become inflamed in a person suffering from rheumatoid arthritis.
Like rheumatoid arthritis, lupus (systemic lupus erythematosus, or SLE) is an autoimmune problem. The body attacks healthy body tissue, such as the synovium. Although lupus can be a serious condition and can cause problems in several parts of the body, the swelling in a joint and the joint damage are often less severe than in rheumatoid arthritis.
In gout, a substance called uric acid builds up in the blood. There are many possible causes of an increased uric acid level. They include dietary factors, obesity, certain medical conditions and medications, genetics, and age.
Excess uric acid is deposited as crystals in joints and sometimes in other body parts as well. The crystals cause the synovium to become inflamed. Gout often develops in the big toe, resulting in swelling, redness, warmth, and severe pain.
Men generally have a higher uric acid level and are more likely to develop gout than women. After menopause, however, a woman's uric acid level begins to rise and she becomes more susceptible to developing the condition.
Transient or Toxic Synovitis
Transient synovitis is a temporary condition that is also called toxic synovitis. It often causes hip pain and limping in young children. The disorder is more common in boys than girls. Generally one hip is affected, but the pain may start in one hip and then move over to the other one. The problem is thought to be caused by a viral infection that triggers inflammation of the synovium in the hip joint. The affected child usually has a mild fever. The virus may cause other symptoms, such as a cold or stomach flu.
Transient synovitis is unpleasant for the child and can be worrying for the parents, but it may not be a serious condition. A doctor must be consulted for a diagnosis and treatment if it develops, however. The condition is frequently treated with anti-inflammatory drugs, pain medications, and rest. It's usually gone in one or two weeks, although it can last for a month or more. Some unlucky children have a tendency to develop transient synovitis whenever they have a cold or another viral infection.
Doctors say that transient synovitis doesn't cause permanent joint damage. However, it's very important to see a physician to get a correct diagnosis because the symptoms may indicate a more serious problem called septic arthritis. This is caused by a bacterium instead of a virus and can result in long-term joint damage.
Transitory synovitis is almost always restricted to children up to the age of ten. There have been a few reports of the disease appearing in adults, however.
Pigmented Villonodular Synovitis
Pigmented villonodular synovitis (PVNS) usually affects the knee or the hip, but it may develop in other joints instead. In PVNS, the synovium grows and becoming larger than normal. It may also form folds (villi). The condition is sometimes referred to as a benign tumor. A benign tumor isn't cancerous and doesn't spread through the body. PVNS is often progressive, however, and gradually becomes worse.
In PVNS, the entire synovium may be enlarged (diffuse PVNS), or the enlargement may be in only one place (localized PVNS). Sometimes enlarged tissue forms a nodule that is attached to the synovium by a stalk. Another feature of the condition is the buildup of a chemical called hemosiderin in the synovium. Hemosiderin contains iron and is yellow-brown in color.
The main symptoms of PVNS are usually pain and swelling in the joint. The swelling is sometimes impressive. A patient may also discover that the affected joint locks. Unfortunately, the cause of pigmented villonodular synovitis is currently unknown. In some people, it develops after an injury to the joint.
Possible Treatments for the Inflammation
A person with synovitis should be under a doctor's care. The first line of treatment is often the use of anti-inflammatory drugs. These may be NSAIDs (nonsteroidal anti-inflammatory drugs) such as aspirin or ibuprofen, or more powerful corticosteroids, which may be given in the form of cortisone injections. Specialized medications like antirheumatic drugs may also be prescribed.
If synovitis lasts for a long time and doesn't respond to other treatments, a synovectomy may be performed to provide relief. This may be either a partial synovectomy (removal of part of the synovium) or a total synovectomy (removal of the entire synovium). The synovium may be removed by surgery, injection of a radioactive isotope into the joint, or the application of chemicals that destroy it.
It's important that a patient discusses the condition with their doctor. The physician will be able to suggest the most appropriate treatment for the patient's problem. He or she will also know about any new treatments that have appeared.
The synovium is a useful structure when it's functioning properly. When it's damaged, however, it can cause a lot of pain. Medical treatments for synovitis can be very helpful. Some cases may be more challenging to treat than others, though. Hopefully, new and improved treatments will soon be available.
- Synovial Joints from the University of British Columbia
- Toxic or Transient Synovitis from the NIH (National Institutes of Health)
- Pigmented Villonodular Synovitis from the American Academy of Orthopaedic Surgeons
- Synovial Inflammation in Osteoarthritis from the NIH
This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.
© 2012 Linda Crampton
Linda Crampton (author) from British Columbia, Canada on April 26, 2013:
Hi, bluebird 156. I am so very sorry about your problems. However, I'm a writer, not a doctor. I can't offer medical advice to individuals. Perhaps you could consult a different doctor and get another opinion about your situation. Sometimes different doctors have different ideas about how to treat a health problem. I hope you find a solution.
bluebird 156 on April 26, 2013:
This ha been very interesting and helpful, but I would really like to know more about how to treat my symptoms. I am 68 , strong, healthy and active. I have long suffered from osteoarthritis in my hands and knees which I have effectively controled with diet and exercise - using NSAIDS only when necessary for painful flair-ups. I still walk without a limp and, until this began, climbed, walked and danced like a young person. Then, nearly two years ago I fell on an irregular flight of stone steps, no obvious injury to anything but my pride. About a week later my right knee began to ache and I consulted the doctor, who without xray diagnosed a strained lateral longitudinal ligament recommending ice and NSAIDS. When the aching became worse and a small lump appeared on the side of my knee I returned and was told to contiue as before. After several more visitist over 18 months my doctor chastised me for "not having reported" the problem earlier! and finally did an xray which showed a small "foreign body" in the knee cavity and a ganglion cyst on the side of the knee which he said contained leaking synovial fluid. he diagnosed a tiny tear in the meniscus and referred me to an orthopedic surgeon for surgery. The OS did an MRI on the joint, discounted the existence of any actual foreign material there (the foreign body he said was a small atypical bone that floats in the joints of a minority of people). He went on to say that my joint loked fine, that all the "mechanical parts of my knee were in excellent condition, though there was slight evidence of osteoarthritis. He found no evidence of any tear in the meniscus and said the fluid leakage (by then the cyst had grown and there was fluid also infitrating the muscles in the front and side of the leg) was atypicical, in that it was in areas where synovial fluid does not usually leak. His diagnosis was that the OA was causing this leakage and that nothing could be done about it. Essentially," you are old go home and suck it up!" The condition has continued to worsen with swelling (no reddness or inflamation) increasing and spreading. My knee aches all the time and, now, the right ankle is becoming painful (I suspect because of changes this has caused in my gate. Is this really the beginning of the end or is there something I can do to maintain my health and believe that staying active is key in doing so.
Linda Crampton (author) from British Columbia, Canada on April 06, 2012:
Thank you very much, drbj!! I appreciate your visit and your kind comment.
drbj and sherry from south Florida on April 06, 2012:
Alicia - you have the knack of presenting information that others might find complicated to read, in an organized easy-to-understand fashion. That is talent, m'dear.
Linda Crampton (author) from British Columbia, Canada on April 05, 2012:
Hi, Joyce. I'm sorry about your rheumatoid arthritis diagnosis and about your other health problems, but I'm glad that the medications are helping. I hope that you continue to find relief from discomfort! Thank you very much for the comment.
Joyce Haragsim from Southern Nevada on April 05, 2012:
Great hub, I found out on Monday that I have RA so I'm on three more meds. which are helping a lot. Also I have brusitis in my shoulders and a cyst behind each knee and I'm just 64. I told my husband take me and shoot me now, kidding. Thanks for putting this hub. Joyce
Linda Crampton (author) from British Columbia, Canada on April 05, 2012:
Hi, billybuc. Thanks for the visit and for commenting! I agree, it's very important to be aware of possible health problems that may develop as we age.
Linda Crampton (author) from British Columbia, Canada on April 05, 2012:
Hi, teaches. Thanks for the comment and the vote. I've seen claims on the Internet that some alternate treatments such as acupuncture or the use of certain herbs or natural chemicals can help synovitis, but I haven't yet found any scientific evidence that these treatments work. It would be great to avoid pharmaceutical medications or surgery as a treatment.
Bill Holland from Olympia, WA on April 05, 2012:
Thank you for the information. I am sixty-three years old and in remarkably good health but I know my time is coming. The more information like this that I can read the better my chances of being pro-active with my health.
Dianna Mendez on April 05, 2012:
I am hearing more of this ailment from people of all ages. Is it something we are eating or not eating? It's a puzzle for sure. I see that the treatments for this are limited to medication and was wondering if other natural resources would supplement in pain relief. Great article and well written. Voted up.
Linda Crampton (author) from British Columbia, Canada on April 04, 2012:
Thank you for the visit and the comment, hetty frederik!
hetty frederik from Jl. Jambu 13 Complex Arco, Sawangan Depok West Java Indonesia on April 04, 2012:
useful information for seniors who are often plagued with such complaints