Classification of Psoriatic Arthritis
Just like psoriasis, psoriatic arthritis ranges from mild to severe. The number of joints affected will have a large impact on the particular treatment plan a rheumatologist will recommend, and the prognosis for an individual. Even a small number of inflamed joints, however, can have a profound impact on pain and function and factors into the treatment decisions.
Psoriatic arthritis of a mild form is sometimes referred to as oligoarticular, meaning it affects four or fewer joints in the body. Others may have a more severe polyarticular form (affecting four or more joints). All types of psoriatic arthritis (PsA) are characterized by pain, swelling and stiffness in the joints.
Psoriatic arthritis can involve the peripheral joints (the joints of your arms and legs, including the elbows, wrists, hands and feet) or less commonly, the axial skeleton (primarily your spine, hips and shoulders).
Spondylitis is inflammation of the spinal column. It is present in some individuals with psoriatic arthritis and it commonly occurs with other forms of psoriatic arthritis. The main symptoms are inflammation with stiffness of the neck, lower back and sacroiliac joints. Spinal arthritis makes joint motion in these areas painful and difficult.
Enthesitis refers to inflammation of entheses, the site where ligaments or tendons insert into the bones. Common locations for enthesitis include the bottoms of the feet, the Achilles' tendons, and the places where ligaments attach to the ribs, spine, and pelvis. It is a distinctive feature of psoriatic arthritis and does not occur with other forms of arthritis like rheumatoid arthritis or osteoarthritis. Enthesitis can make the tissues in the affected area become ropey (known as fibrosis) or solid (known as ossification or calcification).
Dactylitis, or "sausage digits," refers to inflammation/swelling of an entire finger or toe. It occurs due to inflammation of the small joints and enthesitis of the surrounding tendons. Dactylitis is another distinguishing indicator of psoriatic arthritis. Usually dactylitis involves a few fingers and/or toes, but not in a symmetric pattern (different toes and fingers are affected on different sides of the body).