Hydroxyapatite deposition disease (HADD) has a way of arriving without warning — a sudden, severe episode of joint pain, imaging that confirms calcific deposits in a tendon, and a clinical visit that ends with anti-inflammatories and a recommendation to wait it out.

If you've been diagnosed with calcific tendinitis, you already know the pattern: calcium crystals form inside a tendon — most commonly the supraspinatus in the shoulder — and cause pain that ranges from a dull background ache to sudden, acute attacks that make simple movements nearly impossible.