What is psoriatic arthritis? Psoriatic arthritis can occur in people who have psoriasis (scaly red and white skin patches). It affects the joints and areas where tissues attach to bone. The joints most often affected are: The outer joints of the fingers or toes. Wrists. Knees. Ankles. Lower back.
What are sprains and strains? A sprain is an injury to a ligament (tissue that connects two or more bones at a joint). When a sprain happens, one or more ligaments is stretched or torn. A strain is an injury to a muscle or tendon (fibrous cords of tissue that connect muscle to bone). In a strain, a muscle or tendon is stretched or torn.