In medicine

Medicine

Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

, a joint injection (intra-articular injection) is a procedure used in the treatment of inflammatory joint conditions

Inflammation

Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

, such as rheumatoid arthritis

Rheumatoid arthritis

Rheumatoid arthritis is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks synovial joints. The process produces an inflammatory response of the synovium secondary to hyperplasia of synovial cells, excess synovial fluid, and the development...

, psoriatic arthritis

Psoriatic arthritis

Psoriatic arthritis is a type of inflammatory arthritis that, according to the National Psoriasis Foundation, will develop in up to 30 percent of people who have the chronic skin condition psoriasis...

, gout

Gout

Gout is a medical condition usually characterized by recurrent attacks of acute inflammatory arthritis—a red, tender, hot, swollen joint. The metatarsal-phalangeal joint at the base of the big toe is the most commonly affected . However, it may also present as tophi, kidney stones, or urate...

, tendinitis, bursitis

Bursitis

Bursitis is the inflammation of one or more bursae of synovial fluid in the body. The bursae rest at the points where internal functionaries, such as muscles and tendons, slide across bone. Healthy bursae create a smooth, almost frictionless functional gliding surface making normal movement painless...

 and occasionally osteoarthritis

Osteoarthritis

Osteoarthritis also known as degenerative arthritis or degenerative joint disease, is a group of mechanical abnormalities involving degradation of joints, including articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking, and sometimes an effusion...

. A hypodermic needle is injected into the affected joint

Joint

A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...

 where it delivers a dose of any one of many anti-inflammatory

Anti-inflammatory

Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. Anti-inflammatory drugs make up about half of analgesics, remedying pain by reducing inflammation as opposed to opioids, which affect the central nervous system....

 agents, the most common of which are corticosteroid

Corticosteroid

Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...

s. Hyaluronic acid, because of its high viscosity

Viscosity

Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

, is sometimes used to replace bursa

Bursa (anatomy)

A bursa is a small fluid-filled sac lined by synovial membrane with an inner capillary layer of slimy fluid . It provides a cushion between bones and tendons and/or muscles around a joint. This helps to reduce friction between the bones and allows free movement...

fluids. The technique may be used to also withdraw excess fluid from the joint.