Arthritis Today

Glossary P

Browse the glossary by selecting a letter or by entering an arthritis-related term:


A sensation or perception of hurting, ranging from discomfort to agony, that occurs in response to injury, disease or functional disorder. Pain is the body’s alarm system, signaling that something is wrong.


The knee cap, or bone that sits over the other bones at the front of the knee joint and slides when the leg moves. It protects the knee and gives leverage to muscles.


A form of juvenile rheumatoid arthritis characterized by the initial involvement of four or fewer joints.

Pediatric rheumatologist

A doctor who specializes in diagnosing and treating arthritis and related conditions in children.


Physical therapist (PT)

A licensed healthcare professional trained to use exercise to treat medical conditions and create rehabilitation treatment plans. A PT may prescribe canes and splints and some are trained in massage.

Placebo effect

A phenomenon in which a person, who is receiving an inactive drug or treatment, experiences a reduction in symptoms, as if he or she were receiving the active drug or treatment.

Plantar fasciitis

An inflammation of the plantar fascia, the tendon-like structure on the bottom of the foot that extends from the heel to the ball of the foot, maintaining support of the arch. Inflammation may occur for a number of reasons, including changes in activity, weight gain and improper shoes.


A doctor who specializes in diagnosing and treating diseases of the foot. Also called a doctor of podiatric medicine (DPM), a podiatrist receives a DPM degree from one of the seven colleges of podiatric medicine and must complete a two- or three-year residency, or hands-on training, prior to practicing.


A form of juvenile rheumatoid arthritis characterized by the initial involvement of more than four joints.


A disease in which generalized weakness results from inflammation of the muscles, primarily those of the shoulders, upper arms, thighs and hips. When muscle weakness is accompanied by a skin rash, the diagnosis is dermatomyositis.

Protein A immunoadsorption therapy (Prosorba)

A treatment for rheumatoid arthritis that involves filtering the blood plasma through a special column to remove antibodies associated with RA.


Hormonelike substances in the body that play a role in pain and inflammation among other body functions. Nonsteroidal anti-inflammatory drugs work by blocking the production of prostaglandins.

Proton pump inhibitors (PPIs)

A type of medication that blocks an enzyme in the wall of the stomach to reduce the production of stomach acids. PPIs are used to prevent and treat problems such as ulcers or gastroesophageal reflux disease (GERD) caused or aggravated by excess stomach acid.


A skin disease characterized by thickened, inflamed patches of skin covered by silver-gray scales. Between 10 percent and 30 percent of people with psoriasis develop an associated arthritis referred to as psoriatic arthritis. A small percentage develop the associated arthritis before the skin disease.

Psoriatic arthritis

A form of arthritis that is accompanied by the skin disease psoriasis.


Purines are part of all human and animal tissue – they are important in the formation of genetic material, such as DNA and RNA. Many foods derived from animals, especially those high in protein, are high in purines. It is generally recommended that people with gout avoid diets rich in purines because purine breaks down into uric acid, which can crystallize in the joints of people with gout and cause pain.

Predict Your Joint Pain

Predict your joint pain level based on the local weather.