15 DD dealt with elbow locking and has now been to sports med doc and PT specialized in throwing motion. Shes now throwing without pain. At 5'6" she has a scoliosis curve that thankfully does not require treatment but along the journey the ortho said "he sees so many athletes that are all strong in arms and legs, but they couldn't do a plank to save their life". DD PT focused on Core Strengthening as part of weakness impairing her ability to throw properly. Her balance and scapula movement are so much better - she "cross trains" in fall as HS soccer goalie. It's all about keeping the ball in front, right. Her game has improved so much. Anyway-No one had mentioned Core Strengthening, and I think it has been a key for her.