Calcific tendinitis (also called calcific tendinopathy) happens when calcium builds up in the tendons. It is most common in the shoulders. But it may occur in the elbows, wrists, hands, hips, knees, or feet. People most affected by calcific tendinitis are between 30 and 50 years old. Women are more likely to have it than men. It isn't normally a sports-related problem.