There are around 200 types of arthritis – or musculoskeletal conditions – which are split into seven main groups:
- Inflammatory arthritis
- Degenerative or mechanical arthritis
- Soft tissue musculoskeletal pain
- Back pain
- Connective tissue disease
- Infectious arthritis
- Metabolic arthritis.
See also: “Arthritis Diagnosis“
Inflammation is a normal part of the body’s healing process. The inflammation 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.
The inflammation in inflammatory arthritis does not help to repair the body. Instead, it causes the tissues in and around the affected joints to become damaged, causing pain, stiffness and swelling.
The word “arthritis” means “joint inflammation,” but inflammation may also affect the tendons and ligaments surrounding the joint – known as enthesitis.
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:
- Reactive arthritis
- Ankylosing spondylitis
- Arthritis associated with colitis or psoriasis.
Degenerative or mechanical arthritis
Degenerative or mechanical arthritis refers to a group of conditions where damage to the cartilage that covers the ends of the bones is the primary issue. The main job of the smooth, slippery cartilage is to help the joint glide and move smoothly. This type of arthritis causes the cartilage to become thinner and rougher.
The bone underneath the cartilage attempts to repair the damage caused, but, as a result, sometimes overgrows, altering the shape of the joint. 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.
Soft tissue musculoskeletal pain
Soft tissue musculoskeletal pain is felt in tissues other than the joints and bones. The pain often affects a part of the body following injury or overuse, such as tennis elbow, and originates from the muscles or soft tissues supporting the joints.
Sometimes if the pain is more widespread and associated with other symptoms, it could be diagnosed as fibromyalgia.
Back pain can arise from the muscles, discs, ligaments, bones or joints. Back pain may even be caused by problems with organs inside the body – known as “referred pain.”
There can be a specific causes for back pain including conditions such as osteoarthritis, which is often called spondylosis when it occurs in the spine. A “slipped” disc is another cause of back pain, as is osteoporosis (thinning of the bones. In most cases it is not possible for a doctor to identify the exact cause of pain – this is often described as “non-specific” pain.
Connective tissue disease (CTD)
Connective tissues are tissues that support, bind together or separate other body tissues and organs. They include tendons, ligaments and cartilage.
Joint pain is a symptom of CTD, but inflammation may occur in other tissues including the skin, muscles, lungs and kidneys. This results in a range of symptoms besides painful joints and a number of different specialists to be seen in addition to a doctor.
Examples of CTD include:
- Scleroderma (systemic sclerosis)
A bacterium, virus or fungus entering the joint can sometimes cause inflammation. Organisms that can infect joints include:
- Salmonella and shigella (food poisoning or contamination)
- Chlamydia and gonorrhea (sexually transmitted diseases)
- Hepatitis C (a blood-to-blood infection, often through shared needles or transfusions).
In most of these cases, the joint infection can be cleared with antibiotics. However, the arthritis can sometimes become chronic.
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 in urine. Some people have elevated levels of uric acid because they either naturally produce more than is needed 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.
Some of the more common types of arthritis are discussed below.