About 10%-15% of people with psoriasis, a chronic inflammatory skin condition, also develop arthritis. The inflammation of the skin can precede the joint inflammation by years in some cases. Symptoms of psoriatic arthritis arise from inflammation and resemble those of other kinds of arthritis. The joints of the knees, ankles, and feet are commonly involved. Psoriatic arthritis can also cause inflammation in the spine and the eyes, skin, heart, kidneys, mouth, and various organs and is one of the forms of arthritis known as "spondyloarthropathies."

Psoriatic arthritis symptoms and signs include

• joint aches and stiffness,
• joint swelling,
• joint warmth and redness,
• joint pain and tenderness,
• loss of range of motion of the affected joints.

If the spine is affected, there can be pain and stiffness in the low back, buttocks, neck, and upper back. Tendons can also become inflamed, and if Achilles tendinitis is present, other symptoms can include limping, pain with walking, and pain with climbing stairs. Inflammation of the chest wall, lungs, and aorta can cause chest pain and shortness of breath.

Source: http://www.rxlist.com