What is arthritis?
Arthritis refers to more than 100 rheumatic diseases and conditions that affect joints. These conditions tend to involve pain, aching, stiffness, and swelling in and around one or more joints.
The word “arthritis” means “joint inflammation.” However, inflammation may also affect the tendons and ligaments surrounding the joint. The symptoms can develop gradually or suddenly and may impair a person’s ability to perform everyday tasks.
Types of arthritis
There are more than 100 types of arthritis. Generally, arthritis can be split into the following categories:
Inflammatory arthritis
Inflammation is a normal part of the body’s healing process. It tends to occur as a defense against viruses and bacteria or as a response to injuries such as burns. However, with inflammatory arthritis, inflammation occurs in people for no apparent reason.
Inflammatory arthritis is characterized by damaging inflammation that does not occur as a normal reaction to injury or infection. This type of inflammation is unhelpful and instead causes damage to the affected joints, resulting in pain, stiffness, and swelling.
Inflammatory arthritis can affect several joints, and the inflammation can damage the surface of the joints and also the underlying bone.
Examples of inflammatory arthritis include:
- RA
- reactive arthritis
- ankylosing spondylitis
- psoriatic arthritis
Degenerative or mechanical arthritis
Degenerative or mechanical arthritis refers to a group of conditions that mainly involve damage to the cartilage that covers the ends of the bones.
The main job of the smooth, slippery cartilage is to help the joints glide and move smoothly. This type of arthritis causes the cartilage to become thinner and rougher.
To compensate for the loss of cartilage and changes in joint function, the body begins to remodel the bone in an attempt to restore stability. This can cause undesirable bony growths to develop, called osteophytes. The joint can become misshapen. This condition is commonly called osteoarthritis.
Osteoarthritis can also result from previous damage to the joint such as a fracture or previous inflammation in the joint.
Connective tissue disease (CTD)
Connective tissues support, bind together, or separate other body tissues and organs. They include tendons, ligaments, and cartilage.
CTD involves joint pain and inflammation. The inflammation may also occur in other tissues, including the skin, muscles, lungs, and kidneys. This can result in various symptoms besides painful joints, and it may require consultation with a number of different specialists.
Examples of CTD include:
- SLE, or lupus
- Scleroderma, or systemic sclerosis
- dermatomyositis
- Sjogren’s
Infectious arthritis
A bacterium, virus, or fungus that enters a joint can sometimes cause inflammation.
Organisms that can infect joints include:
- salmonella and shigella, which spread through food poisoning or contamination
- chlamydia and gonorrhea, which are sexually transmitted diseases (STDs)
- hepatitis C, which is a blood-to-blood infection that may be spread through shared needles or transfusions
A doctor can treat a joint infection with antibiotics or other antimicrobial medication. However, the arthritis can sometimes become chronic, and joint damage may be irreversible if the infection has persisted for some time.
Metabolic arthritis
Uric acid is a chemical created when the body breaks down substances called purines. Purines are found in human cells and several foods.
Most uric acid dissolves in blood and travels to the kidneys. From there, it passes out of the body in urine. Some people have high uric acid levels because they either naturally produce more than they need or their body cannot clear the uric acid quickly enough.
Uric acid builds up and accumulates in some people and forms needle-like crystals in the joint, resulting in sudden spikes of extreme joint pain or a gout attack.
Gout can either come and go in episodes or become chronic if uric acid levels are not reduced.
It commonly affects a single joint or a small number of joints, such as the big toe and hands. It usually affects the extremities. One theory is that uric acid crystals form in cooler joints, away from the main warmth of the body.
Childhood arthritis
This can refer to a number of types of arthritis. Juvenile idiopathic arthritis (JIA), also known as juvenile rheumatoid arthritis (JRA), is the most common type.
Arthritis in childhood can cause permanent damage to joints, and there is no cure. However, remission is possible, during which time the disease remains inactive.
It may be due to immune system problems.
Septic arthritis
Septic arthritis is a joint inflammation that results from a bacterial or fungal infection. It commonly affects the knee and hip. It typically affects 2-6 people per 100,000.
It may develop when bacteria or other disease-causing microorganisms spread through the blood to a joint, or when the joint is directly infected with a microorganism through injury or surgery.
Bacteria such as Staphylococcus, Streptococcus, or Neisseria gonorrhoeae cause most cases of acute septic arthritis. Organisms such as Mycobacterium tuberculosis and Candida albicans cause chronic septic arthritis. This is less common than acute septic arthritis.
The following conditions increase the risk of developing septic arthritis:
- existing joint disease or damage
- artificial joint implants
- bacterial infection elsewhere in the body
- presence of bacteria in the blood
- chronic illness or disease (such as diabetes, RA, and sickle cell disease)
- intravenous (IV) or injection drug use
- medications that suppress the immune system
- recent joint injury
- recent joint arthroscopy or other surgery
- conditions such as HIV, that weaken immunity
- diabetes
- older age
Septic arthritis is a rheumatologic emergency as it can lead to rapid joint destruction. It can be fatal.