Inflammatory arthritis can be roughly divided up into three groups.

Monoarticular, meaning one joint is involved; oligoarticular, meaning more than one but less than four or five joints; and polyarticular, meaning more than five joints are involved.

This article will focus on the oligoarticular type of presentation.

This group can be subdivided into whether they are acute or chronic.

Acute oligoarticular inflammatory arthritis (AIOA) may be due to bacterial infection... what is termed septic arthritis. This can be due to many types of bacteria. Risk factors include immunosuppression, history of intravenous drug abuse, and preexisting arthritis such as rheumatoid arthritis. This condition is always considered a medical emergency.

Other bacteria such as gonococcus (the bacteria that causes gonorrhea) and meningococcus (the bacteria that causes meningitis) both can cause AIOA.

Patients with these diseases may have a characteristic rash on the arms or legs.

Fungal infections can do this as can bacterial endocarditis, infection involving the heart valves.

Lyme disease classically causes AIOA that preferentially attacks the knees.

A rarer type of AIOA is associated with Whipple's disease, a bowel affliction caused by a bacteria.

Reactive arthritis- also known as Reiter's disease- is a form of arthritis associated with urinary tract or bowel infection. This disease can cause an AIOA that is associated with swollen fingers and toes, mouth sores, and inflammation of the eyes.

Sarcoidosis is an enigmatic autoimmune disease that affects multiple organ systems including the lungs, heart, eye, and brain. It can cause AIOA that affects the ankles and knees. It tends to come on most commonly in the spring.

Palindromic rheumatism is another cause of AIOA. This a peculiar form of arthritis that causes recurrent attacks of joint inflammation. The attacks jump from joint to joint. They occur suddenly, are very painful, occur irregularly, last a few hours to a few days, and then go away. Often patients with palindromic rheumatism go on to develop rheumatoid arthritis.

Cancer can cause a sudden AIOA, generally involving the legs.

Some patients with a history of elevated lipids may also develop AIOA.

Let's move onto the chronic types of oligoarticular inflammatory arthritis. Disease such as psoriatic arthritis (the arthritis associated with psoriasis) is a chronic type of oligoarticular inflammatory arthritis that is associated with the skin manifestations of psoriasis. These patients may also have inflammation at tendon insertions and inflammatory eye disease.

Likewise, ankylosing spondylitis, an inflammatory arthritis that preferentially attacks the spine can cause AIOA. It may also be associated with tendon inflammation and eye involvement.

Inflammatory bowel disease is another condition that is associated with AIOA that tends to attack the legs, most commonly, the toes, ankles, and knees.

Rheumatoid arthritis rarely presents in an oligoarticular fashion. But when it does, gradually joints then tend to "add on" until the classic symmetric inflammatory picture develops.

As the list suggests, an accurate diagnosis is important in establishing a proper treatment plan. Unfortunately, it may take time for the diagnosis to make itself clear. Effective arthritis treatment hinges on the proper diagnosis.This can be frustrating for both the patient as well as the rheumatologist.