Our son is a high school football player. When he plays offensive lineman he complains afterwards of shoulder pain. He says when he uses his arms in the blocking position and comes up against another player, his left shoulder "gives way." Is this something we should talk to the coach about?
It's possible your son is having some shoulder instability. The head of the humerus, a round ball at the top of the upper arm bone may be moving backwards out of the joint. This is called subluxation if it's not fully dislocating.

Repetitive loading in the blocking position can put the shoulder at risk for instability from dislocation. You should talk with the coach or trainer but the best thing may be to see an orthopedic surgeon. X-rays, scans, and special tests may be needed to accurately diagnose the problem.

A special rehab program designed for this problem should be tried before jumping into surgery. Most of the time there's a muscle imbalance that can be overcome with the right kind of strength training. The joint itself may have to regain its full joint sense of position called proprioception. The physical therapist will also address this problem during rehab.

Early detection and intervention are the keys to getting back on the field and staying there without further injury. Don't put this off when it may be a small problem and before surgery or other invasive treatment is needed.