Yes. Lots of medication contains steroid and that's why players have to be very careful with whatever they take. and yes, cortizone injection is used to treat tendon problems. I had a few myself for the left wrist
. It is OK for Murray to take these shots for treatment as long as he filed the correct papers with doctors signature and also, he was out of competition.
But if Nole really has this dipigmentation problem and he uses this cream, there is no control on how much of the chemicals in the cream will be absorbed into his body and he is in competition. Remember Voladri got into trouble because he took more than was allowed from his inhaler for asthma he sufferred in IW because it was dusty and windy that day.
But he wasn't out of competition. He took the cortizone injections for his elbow before coming on to play his match with Nadal in Monte Carlo. Apparently he injured it in his warm up that morning. They(Sky) were all talking about his injury and his shots so he could play the match etc., because they're British broadcasters.