Lesson learned.. be very cautious if the range of motion becomes impaired.
At age 13, my son began to experience a decrease in his throwing elbow range of motion. There was no pain and no noticeable loss of velocity but the condition persisted for several weeks. We had always been very careful with pitch counts and he was not allowed to pitch during winter ball. But we became concerned when he started to experience some minor inflammation and soreness.
We found out that he had OCD (osteochondritis dessicans) which is damage to the cartilage and bone in the joint. This condition can be caused by overuse, but can also be initiated by some trauma that causes bloodflow deprivation to the joint. He had to have microfracture surgery followed by 6 months of rest and physical therapy. The procedure was successful and he was cleared to resume playing. But it might have been possible to avoid surgery if he had shut it down and rested his arm when he first started to experience the decrease in range of motion.