Patients who have psoriasis, a chronic autoimmune skin condition that causes rapid skin cell growth and renewal, can develop psoriatic arthritis, a type of inflammatory arthritis. Psoriatic arthritis is different from other forms of arthritis because it involves the skin and it affects the joints differently.
The majority of psoriatic arthritis patients develop the rash of psoriasis before they develop psoriatic arthritis, though some may experience joint pain before the rash, or both symptoms may occur at the same time.
Psoriatic arthritis rashes can look different on different patients. Some people may have localized rashes in a few small patches, while others may develop a rash all over the body.
Psoriatic arthritis rash commonly appears on the scalp, elbows, knees, and around the ears and looks like red patches of skin with silvery scales (plaques).
Other types of psoriatic rashes include:
- Erythrodermic psoriasis
- Redness and scaling generalized over a large portion of the body
- Guttate psoriasis
- Small, dots or lesions shaped like tear drops, usually appearing on the trunk, upper arms, and thighs
- Inverse psoriasis
- Pustular psoriasis
What Are Psoriatic Arthritis Symptoms?
In addition to a skin rash, symptoms of psoriatic arthritis include:
- Skin itching
- Skin warmth and redness
- Thickening skin
- Joint pain, swelling, and stiffness
- Usually on one side of the body
- Pain may worsen in the morning or after rest
- Often affects large joints of lower extremities such as knees and ankles but can affect any joint
- Back, hip, and shoulder pain
- Reduced range of motion in the joints
- Pain and stiffness in the lower back and neck
- Swelling of fingers and/or toes
- Fatigue
- Heel and foot pain
- Nail problems such as pitting, crumbling, and separating from nail bed
- Eye inflammation such as pink eye (conjunctivitis) and other infections
What Psoriatic Arthritis Medications Are Available?
Because there is no cure for psoriatic arthritis, treatment will involve medications used to relieve symptoms and prevent further joint damage.
Nonsteroidal anti-inflammatory drugs (NSAIDs) used for mild psoriatic arthritis to treat pain and inflammation include:
- Over-the-counter (OTC)
- Aspirin
- Ibuprofen (Advil, Motrin)
- Naproxen (Aleve)
- Prescription
- Celecoxib (Celebrex)
Treatments for severe cases of psoriatic arthritis include:
- Corticosteroid injections into the joints
- Disease-modifying antirheumatic drugs (DMARDs)
- Azathioprine (Azasan)
- Apremilast (Otezla)
- Methotrexate (Rasuvo, Otrexup, Xatmep, Trexall)
- Sulfasalazine (Azulfidine EN-tabs, Azulfidine)
- Leflunomide (Arava)
- Hydroxychloroquine (Plaquenil)
- Antitumor necrosis factor (TNF) agents (also called biologics)
- Ixekizumab (Taltz)
- Secukinumab (Cosentyx)
- Tofacitinib (Xeljanz)
- Abatacept (Orencia)
- Ustekinumab (Stelara)
- Topical treatments for psoriasis symptoms
- Over-the-counter or prescription salicylic acid creams, gels, and shampoos
- Prescription vitamin D creams
- Retinoid and steroid creams
- Immunosuppressant
- Cyclosporine (used for severe cases that do not respond to other systemic treatments)
From 
https://www.niams.nih.gov/Health_Info/Psoriatic_Arthritis/default.asp
https://www.uptodate.com/contents/psoriatic-arthritis-beyond-the-basics
https://creakyjoints.org/