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What is arthritis?

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There are about 200 different musculoskeletal conditions, which fall into five main groups:

Inflammatory arthritis

Arthritis literally means inflammation within the joint itself. Inflammation is part of your body's healing process. It normally occurs as a defence against viruses and bacteria or as a reaction to injuries such as a burn.

But in people with this type of arthritis, inflammation often occurs for no obvious reason. This is referred to as an autoimmune condition and means that the immune system is attacking your joints. Instead of helping to repair the body, inflammation can cause damage to the affected joint and cause pain and stiffness.

Inflammation may also affect the tendons and ligaments surrounding the joint.

Inflammatory types of arthritis often affect several joints. Rheumatoid arthritis, which is a common example, is a systemic illness that mainly affects the joints. As well as joint pain and swelling, other symptoms of rheumatoid arthritis can include:

  • tiredness
  • depression
  • irritability
  • flu-like symptoms.

A joint badly affected by rheumatoid arthritis

There are many other forms of inflammatory arthritis, including:

Degenerative or mechanical arthritis

Degenerative arthritis is a group of conditions where the main problem is damage to the cartilage which covers the ends of the bones.

Normally the smooth, slippery cartilage helps the joints to move smoothly. In this type of arthritis the cartilage becomes thinner and rougher, and the bone underneath then tries to repair this damage but sometimes overgrows, altering the shape of the joint. This is known as osteoarthritis.

Osteoarthritis is more common in older people and particularly affects the joints that get heavy use, like hips and knees. It also often affects the base of the thumb and big toe joint.

Osteoarthritis can result from damage to the joint, for example a fracture or previous inflammation in that joint.

A joint that has been deformed by severe osteoarthritis

Soft tissue musculoskeletal pain

Soft tissue musculoskeletal pain is often felt in tissues other than your bones and joints. Typically it will come from the muscles or soft tissues supporting the joints, including the bursa, which can sometimes become inflamed.

You may find this type of pain is localised to one particular part of the body following an injury or overuse. You might find that the pain is more widespread and, if associated with other symptoms, a diagnosis of fibromyalgia may be made. Often the causes of these symptoms are not fully understood.

Back pain

Back pain is a very common problem that has a number of different causes. Pain can come from:

  • muscles
  • discs
  • ligaments
  • bones
  • joints.
It may even be caused by problems with other organs inside your body. This is known as 'referred pain'.

Sometimes there's a specific cause, such as the degenerative condition osteoarthritis. This is often known as spondylosis when it happens in the spine.

Sometimes back pain may be caused by a ‘slipped’ disc. The disc itself doesn't really slip but the central part of the disc bulges through the outer ring. This more commonly causes pain in a limb, though.

Osteoporosis (thinning of the bones) can cause sudden back pain if one of the bones in the spine crunches down.

In most cases it isn't possible to identify the exact cause of the pain, and doctors often describe this as non-specific or simple back pain.

Connective tissue diseases (CTD)

Connective tissues support, bind together or separate other body tissues and organs. They include:

  • tendons
  • ligaments
  • cartilage.

Joints are usually involved in CTD, but there may also be inflammation in other tissues such as the:

  • skin
  • muscles
  • lungs
  • kidneys.
You may therefore feel a range of other symptoms besides painful joints. 

Examples of CTD include lupus (SLE), scleroderma (systemic sclerosis) and dermatomyositis.

Your healthcare team will often include different specialists along with your GP because these diseases often affect many organs.

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