Osteoarthritis and Inflammation - Exploring the Connection

Osteoarthritis in the fingers; a bony enlargement known as a Heberden's node is located next to a fingernail
Osteoarthritis in the fingers; a bony enlargement known as a Heberden's node is located next to a fingernail | Source

The Nature of the Disease

Osteoarthritis is a disorder in which the cartilage in a joint degenerates and eventually disappears. The cartilage normally covers the ends of the bones in a joint and acts as a low-friction cushion between them as the bones move. When the cartilage is absent, the end of one bone rubs against the end of another, causing pain and difficulty in movement. Osteoarthritis is often a symptom of aging, but it may appear at any age due to an injury to a joint.

It was once thought that osteoarthritis was caused solely by wear and tear and involved no inflammation, unlike rheumatoid arthritis. The latter disorder is an autoimmune and inflammatory condition that affects joints and other parts of the body as well. Now researchers know that inflammation is also involved in osteoarthritis. It may not be as severe as that found in rheumatoid arthritis, but it may still be be significant.

Differences Between Osteoarthritis and Rheumatoid Arthritis

Who Gets Osteoarthritis?

Osteoarthritis is the most common form of arthritis. It's also known as degenerative arthritis or degenerative joint disease. Its name is sometimes abbreviated as OA. OA can affect any joint in the body, but it most commonly appears in joints located in the spine, hips, knees, feet or hands.

Research indicates that the majority of people in North America will have some degree of osteoarthritis by the time they are seventy. Not everyone will experience symptoms of the disorder. For some people, however, osteoarthritis is a painful disease. It may also be disabling.

A Synovial Joint

Source

The synovial joint is the most common type of joint in our body and is the site of osteoarthritis development.

What Happens to a Joint in OA?

A joint is a region where two bones meet. The type of cartilage that covers the ends of the bones is known as hyaline cartilage. It's a stiff but flexible material that is very slippery and allows bones to move over each other smoothly with low friction. If this cartilage gradually disappears, as it does in osteoarthritis, the ends of the bones will rub together.

The cartilage in a joint is sometimes known as articular cartilage. The body may form extra bone in a joint that lacks this cartilage. The extra bone forms irregular projections called bone spurs or osteophytes. Pieces of bone spurs may break off and be trapped in the joint, along with broken bits of cartilage. It's generally thought that these bits of bone and cartilage irritate the membrane that lines the joint capsule, causing inflammation, although there are additional theories to explain why the joint lining becomes inflamed.

A Doctor Describes Osteoarthritis

Symptoms of OA

There may be no symptoms of osteoarthritis. Some people experience problems, however, which may be severe.

  • A person with OA may experience pain when moving the affected joint or when putting weight on it.
  • The joint may be stiff, especially after a person wakes up or after they have been inactive for a while.
  • There may be limitation in movement. The presence of osteophytes may further limit movement.
  • Bone spurs in a joint may produce a knobby appearance.
  • There may be a creaking, crackling or grating sound or sensation when the joint is moved. This sound is known as crepitation or crepitus.

Although there are treatments to make osteoarthritis more bearable, there is no cure for the disease, other than replacing the diseased joint with an artificial joint. Therefore researchers are very interested in finding ways to stop the progression of OA.

This toe has become infected after experiencing an ingrown toenail and shows acute inflammation.
This toe has become infected after experiencing an ingrown toenail and shows acute inflammation. | Source

Types of Inflammation

Acute Inflammation

Acute inflammation appears rapidly and lasts for a short period of time. It's a normal body response to an infection or an injury and is usually a beneficial process in our bodies. During acute inflammation, there is increased blood flow to the injured area. The blood carries white blood cells and proteins to fight bacteria and remove damaged tissue cells. The blood vessels become more permeable, allowing the beneficial substances to leave the blood and enter the injured tissue. Possible signs and symptoms of acute inflammation are heat, swelling, redness and pain.

Chronic Inflammation

Chronic inflammation lasts for a long time. It may be weaker than acute inflammation. Sometimes acute inflammation becomes chronic instead of being resolved, however. In chronic inflammation, the concentrations of white blood cells and of proteins associated with the inflammation remain abnormally high and can damage tissues. This can lead to health problems. Both acute and chronic inflammation may be involved in osteoarthritis.

Joint structure, showing the entheses and the synovium (also called the synovial membrane or the synovial lining)
Joint structure, showing the entheses and the synovium (also called the synovial membrane or the synovial lining) | Source

Inflammation in Osteoarthritis

Inflammation is being found in osteoarthritic joints with increasing frequency. The inflammation arises from damage to the synovium that lines the inside of a joint capsule. Some researchers have proposed that the inflammation in the synovium is being caused by inflammation in an enthesis, which is the place where a ligament or a tendon joins to bone.

Ligaments are fibrous structures that join one bone to another at a joint. Tendons are fibrous structures that join muscles to bones at a joint.

What Causes the Joint Inflammation?

The Synovium

The synovium is also known as the synovial membrane or the synovial lining. It covers the inside of the capsule surrounding a joint and produces synovial fluid, which nourishes the articular cartilage.

Inflammation of the synovium is called synovitis. In osteoarthritis, the inflammation is thought to appear when broken pieces of articular cartilage - and broken pieces of bone spurs, if they form - irritate the synovium. However, this doesn't explain all cases of osteoarthritis inflammation. Researchers have been puzzled by the fact that in some cases of early osteoarthrotis, synovitis has existed without cartilage breakdown and without bone spur formation.

The Entheses

Ligaments join bones together and tendons attach muscles to bones. The entheses are transition areas where ligaments and tendons join to a bone: they contain collagen fibers like the ligaments and tendons but also contain minerals like bone.

Some UK scientists have found evidence that an inflamed enthesis influences the synovium in a joint and causes it to become inflamed, too. Once the synovium is inflamed the articular cartilage begins to degenerate. According to this idea, the inflammation of the synovium is the cause of osteoarthritis instead of the result.

Impact of OA

The Significance of the Complement System

There is additional evidence that inflammation may be a cause of osteoarthritis instead of (or as well as) a result of the disease. A research team at Stanford University in the United States has shown that osteoarthritis may develop due to a malfunctioning complement system.

The complement system is part of the immune system. It's normally activated to help other components of the immune system fight infectious bacteria and viruses that have entered the body. It "complements" the action of the rest of the immune system.

The complement system consists of proteins which take part in a series of reactions known as the complement cascade. The process ends with the activation of a special complex of proteins called the membrane attack complex. This complex kills cells by creating holes in their membranes. This is very useful if a cell that is being attacked is a bacterial cell.

Although the complement system is helpful in the fight against harmful microbes, it's dangerous for healthy cells, since its function is to destroy cells. Therefore the body makes control proteins that act as brakes for the complement cascade.

A representation of the membrane attack complex formed by the complement cascade; the letters and numbers represent proteins
A representation of the membrane attack complex formed by the complement cascade; the letters and numbers represent proteins | Source

The Complement System in Osteoarthritis

The research carried out by the Stanford scientists suggests that the first step in the development of osteoarthritis is damage to a joint. As a result of the damage, the complement system is activated.

By extracting and analyzing joint fluid from people with and without osteoarthritis, researchers have found that people with osteoarthritis have an excessive number of proteins that accelerate the complement cascade and a low level of the proteins that stop the cascade compared to the levels in people without osteoarthritis. The researchers believe that in susceptible people the complement system attacks the injured joint, causing inflammation and damage to the articular cartilage.

Reducing the Risk of Osteoarthritis

Tips for Preventing or Delaying Osteoarthritis

Since osteoarthritis often develops due to an injury to a joint, it's very important to try to reduce injuries and to treat them properly if they do happen. Joint degeneration may not be noticed until years after an injury. Although there does seem to be an inherited tendency to develop osteoarthritis in some people, everybody can reduce their risk of joint degeneration by taking some precautions. Here are some tips.

  • It's known that weight gain increases the risk of hip and knee arthritis, since there is increased force exerted on the lower body joints as the person moves. Maintain a healthy weight to reduce the chance of osteoarthritis developing.
  • Exercise to strengthen the muscles around the joint to reduce the chance of injury.
  • Avoid repetitive exercise that stresses a joint.
  • Maintain good posture to protect certain joints from pressure.
  • Do warm-ups before participating in sports.
  • Participate in a variety of exercise activities that emphasize the use of different muscles and joints.
  • Start a new physical activity carefully, gradually increasing the intensity.
  • Wear safety equipment if necessary during an activity, such as knee pads for inline skating.
  • Use proper body mechanics when lifting weights to avoid injury
  • If you are injured, get proper treatment and wait for the injury to heal completely before returning to the activity that caused the injury.

Do You Have Arthritis?

Have you been diagnosed with arthritis?

See results without voting

Some Ways to Relieve Osteoarthritis Pain

Treatments for OA

At the moment, the main treatment for osteoarthritis is the use of pain relievers and anti-inflammatory medications such as acetaminophen (paracetamol) or ibuprofen. These can help remove pain for a while but don't stop the progression of the disease. There are also creams available that relieve pain temporarily when placed on a joint. Some people find that the application of cold or heat makes their sore joints feel better. Doctors may prescribe more powerful medicines than over-the-counter medications. They may also inject potentially helpful substances into a joint, such as corticosteroids or hyaluronic acid.

Physical therapy may be helpful for osteoarthritis in some parts of the body, and so may specific joint exercises. These exercises must be done with medical advice, however, in order to improve the function of the joint instead of making it worse.

The Stanford University researchers hope to find ways to stop the complement cascade in joints in order to end inflammation. This may be tricky, however, because anything that stops the complement cascade in our body may also increase our susceptibility to bacterial and viral infections. If researchers can find a way`to hinder the complement system only in damaged joints and nowhere else in the body they may have an effective way to prevent osteoarthritis, or at least to slow its progression.

Since the incidence of osteoarthritis seems to be increasing in many countries, researchers are trying to understand the disease better in order to find improved treatments. Hopefully these improved treatments will appear very soon.

References and Further Reading

General Osteoarthritis Information from the NIH (National Institutes of Health)

Inflammation of the Enthesis and its Role in Arthritis from Arthritis Research UK

The Complement System and Osteoarthritis from Stanford University

Sokolove J, Lepus CM. Role of inflammation in the pathogenesis of osteoarthritis: latest findings and interpretations. Therapeutic Advances in Musculoskeletal Disease . 2013;5(2):77-94. doi:10.1177/1759720X12467868.

© 2012 Linda Crampton

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Comments 16 comments

Ingenira profile image

Ingenira 4 years ago

Wow, this information is as good as encyclopedia or wikipedia. Thank you for all your hard work ! Excellent article. Voted up and tweeted.


AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

Thank you so much for such a wonderful comment, Ingenira! I appreciate it very much, and I appreciate the vote and the tweet as well.


writer20 profile image

writer20 4 years ago from Southern Nevada

Great article for all with osteo arthritis. I'm on a fairly new med that I inject for my R/A and it seems to be working very well.

Voted up useful and very interesting, Joyce.


AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

I'm so glad that you've found a medication that helps you with your RA, Joyce! I've been told that I have osteoarthritis in my neck, but luckily it's not causing any symptoms, apart from a clicking and creaky sound at times as I move my neck. It would be very nice if scientists could find out more about rheumatoid arthritis, osteoarthritis and the other forms of arthritis, because then they may be able to find better treatments and prevention methods.


writer20 profile image

writer20 4 years ago from Southern Nevada

I'm glad in a sense you go as far as osteo-arthritis. That was what I was diagonise with at first then another blood test showed the Rheumatoid.

Do keep up all your blood tests, please.


AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

Thank you very much for the advice, Joyce. I appreciate it.


Mama Kim 8 profile image

Mama Kim 8 4 years ago

Oh my goodness! That picture of the ingrown toenail infection was horrible! The mother of all ingrowns :/ The women in my family have OA problems in the hands. I'm not looking forward to it, but maybe some of your prevention tips will help. Voted up!


AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

Hi, Mama Kim 8. I think I inherited my tendency to develop osteoarthritis from my mother, who had the same problem. There does seem to be an inherited component to the disorder, at least in some families. I agree with you - that toenail infection does look very unpleasant! Thanks for the vote.


teaches12345 profile image

teaches12345 4 years ago

Alicia, this is very interesting and useful, voted up and as such. Keeping healthy and exercising is such a simple remedy to this condition. I hope that others read this and follow your advice.


AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

Thank you, teaches. I appreciate the comment. Although there's no guarantee that we can avoid osteoarthritis, there are certainly ways in which we can significantly reduce the chance!


drbj profile image

drbj 4 years ago from south Florida

Welcome to the club, Alicia. I'm referring to the C.C.C. - the Creaky Clicking Club. My neck clicks and creaks on demand. Not painful - yet - but annoying. You have written a remarkable, complete treatise on the topic of osteoarthritis that any encyclopedia publisher would be happy to include in the volume labeled 'O.'


AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

Thank you very much for the comment, drbj! I appreciate it. Yes, the C.C.C. club is one I'd rather not belong to!


unknown spy profile image

unknown spy 4 years ago from Neverland - where children never grow up.

you did a great job on this hub Alicia. this is a serious thing and must not taken lightly. thanks for the info!


AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

Thank you very much, unknown spy! I appreciate your visit.


bdegiulio profile image

bdegiulio 11 months ago from Massachusetts

Great information Linda. I sure hope I don't have to face this and so far so good. I try to stay as active as possible but it's interesting to know that injuries can lead to OA. Have a Merry Christmas and a Happy New Year.


AliciaC profile image

AliciaC 11 months ago from British Columbia, Canada Author

Thank you very much, Bill. I hope you stay free of OA. I hope you have a great Christmas and New Year, too!

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