Arthritis is a disease that causes pain and loss of movement of the joints. Joint pain is referred to as arthralgia. Arthritis is the leading cause of disability in people over the age of 55. The causes of arthritis depend on the form of arthritis. Causes include injury (leading to osteoarthritis), abnormal metabolism (such as gout and pseudogout), inheritance, infections, and for unclear reasons (such as rheumatoid arthritis and systemic lupus erythematosus). There are many forms of arthritis .There are about 200 different kinds of arthritis. The most common type is osteoarthritis (or degenerative arthritis), where the cartilage that protects the bones gets worn away. This makes joints stiff, painful and creaky. About 5 million people in the UK have osteoarthritis. OA is a chronic degenerative arthropathy that frequently leads to chronic pain and disability. With the aging of our population, this condition is becoming increasing prevalent and its treatment increasingly financially burdensome. Using radiographic criteria, the distal and proximal interphalangeal joints of the hand have been identified as the joints most commonly affected by OA, but they are the least likely to be symptomatic. Age is the most consistently identified risk factor for OA, regardless of the joint being studied. Prevalence rates for both radiographic OA and, to a lesser extent, symptomatic OA rise steeply after age 50 in men and age 40 in women. Occupation-related repetitive injury and physical trauma contribute to the development of secondary (non-idiopathic) OA, sometimes occurring in joints that are not affected by primary (idiopathic) OA, such as the metacarpophalangeal joints, wrists and ankles.

Rheumatoid arthritis (RA) is traditionally considered a chronic, inflammatory autoimmune disorder. Rheumatoid arthritis occurs when the body's defence mechanisms go into action when there's no threat and start attacking the joints and sometimes other parts of the body. RA affects 2.1 million Americans, or about 1% of the adult population in the United States. This disease is 2 to 3 times more common in women than in men, and generally affects people between the ages of 20 and 50. However, young children can develop a form of RA called juvenile rheumatoid arthritis. Two of the 100 types of arthritis are rheumatoid arthritis and lupus. There are specific symptoms, distinguishing characteristics, as well as overlapping symptoms associated with rheumatoid arthritis and lupus. Rheumatoid arthritis is an additive polyarthritis, with the sequential addition of involved joints, in contrast to the migratory or evanescent arthritis of systemic lupus erythematosus or the episodic arthritis of gout. Occasionally, patients experience an explosive polyarticular onset occurring over 24 to 48 hours. Morning stiffness, persisting more than one hour but often lasting several hours, may be a feature of any inflammatory arthritis but is especially characteristic of rheumatoid arthritis. Its duration is a useful gauge of the inflammatory activity of the disease.

Psoriatic arthritis is related to the skin condition psoriasis. It occurs more commonly in patients with tissue type HLA-B27. There are five clinical patterns of psoriatic arthritis. First is Asymmetrical mono- and oligoarticular arthritis (30-50% of cases) is the most common presentation of psoriatic arthritis. Second is symmetrical polyarticular arthritis (30-50% of cases) is ultimately the most common form of psoriatic arthritis. Third is distal interphalangeal (DIP) joint involvement (25% of cases) is nearly always associated with nail manifestationsm. Fourth is Arthritis mutilans is affects less than 5% of patients and is a severe, deforming and destructive arthritis. This condition can progress over months or years causing severe joint damage. Fifth is Axial arthritis (30-35% of cases) may be different in character from ankylosing spondylitis, the prototypical HLA-B27-associated spondyloarthropathy. It may present as sacro-iliitis, which may be asymmetrical and asymptomatic, or spondylitis, which may occur without sacro-iliitis and may affect any level of the spine in "skip" fashion. Genetic factors appear to play an important role. There is a 70% concordance for psoriasis in monozygotic twins. There is a 50-fold increased risk of developing psoriatic arthritis in first-degree relatives of patients with the disease. Environmental factors have been implicated. Streptococcal infection can precipitate the development of guttate psoriasis. HIV infection can present with both psoriasis and psoriatic arthritis, as well as worsen existing disease.

Gout is one of the most painful types of arthritis. Gout was once incorrectly thought to be a disease of the rich and famous, caused by consuming too much rich food and fine wine. Gout is a disease due to a congenital disorder of uric acid metabolism. Uric acid is produced when purines are broken down by enzymes in the liver. Purines can be generated by the body itself (via the breakdown of cells in normal cellular turnover) or can be ingested in purine-rich foods (e.g. seafood, beer). Gout usually attacks the big toe (approximately 75% of first attacks), however it can also affect other joints such as the ankle, heel, instep, knee, wrist, elbow, fingers, and spine. In some cases the condition may appear in the joints of the small toes which have become immobile due to impact injury earlier in life, causing poor blood circulation that leads to gout. Chronic gout can lead to deposits of hard lumps of uric acid in and around the joints, decreased kidney function, and kidney stones. An acute attack of gout is a highly inflammatory arthritis often with intense swelling, redness and warmth surrounding the joint. The inflammatory component is so intense, an acute attack of gout is often mistaken for a bacterial cellulitis. Gout is mainly treated with anti-inflammatory drugs. Corticosteroids (also called steroids), may be prescribed for people who cannot take NSAIDs. Steroids also work by decreasing inflammation. Steroids can be injected into the affected joint or given as pills. Colchicine is often used to treat gout and usually begins working within a few hours of taking it.

Septic arthritis also known is Pyogenic arthritis. Septic arthritis is infection, usually bacterial, in the joint cavity. Septic arthritis usually affects just one joint, though occasionally it may occur in more than one joint at a time. It is the most dangerous form of acute arthritis. The joint cavity is usually a sterile space, with synovial fluid and cellular matter including a few white blood cells. Many different types of bacteria (germs) can cause septic arthritis. Infection with a bacterium called Staph. aureus is the most common cause. Septic arthritis is inflammation of a synovial membrane with purulent effusion into the joint capsule, usually due to bacterial infection. This disease entity also is referred to in the literature as bacterial, suppurative, purulent, or infectious arthritis. The most common bacterial isolates in native joints include gram-positive cocci, with S. aureus found in 40% to 50% of the cases. Septic arthritis is uncommon from age 3 to adolescence. Children with septic arthritis are more likely than adults to be infected with group B streptococcus and Haemophilus influenza. Young children and older adults are most likely to develop septic arthritis. As the population ages, doctors are finding that septic arthritis is becoming more common. Symptoms of septic arthritis occur suddenly and are characterized by severe pain, swelling in the affected joint along with acute pain. Chills and fever are also common symptoms. Chronic septic arthritis (which occurs less frequently) is caused by organisms such as Mycobacterium tuberculosis and Candida albicans. The knee and the hip are the most commonly infected joints.