Psoriasis is a skin condition which is characterized by buildup of skin cells which form scales and itchy, dry patches. People with psoriasis have a high tendency to be affected with psoriatic arthritis; a form of arthritis that affects people who have a skin condition of psoriasis. In other words, a person who has psoriatic arthritis suffers from inflammation of one or more joints as well as skin cells. 
While psoriatic arthritis patients may not be permanently cured, specific natural remedies exist to manage the symptoms such as the relief of pain, reduction of inflammation, etc.
Derived from a plant in the ginger family, turmeric is known for its immense nutritional and health benefits resulting from its composition of medicinal compounds such as curcumin. Curcumin which is a powerful antioxidant has powerful anti-inflammatory effects. As an antioxidant, the intake of turmeric is capable of neutralizing free radicals. Too many free radicals in the body may cause oxidative stress which is linked to inflammation. Since the pain from psoriatic arthritis is inflammatory induced, consumption of turmeric can help manage the inflammation and relieve the pain. 
Application: Turmeric can be taken as smoothies; it could be added to food recipe or even applied directly to the skin. You could discuss with a health consultant and find the best application method.