When my mom makes a fist the tendons hurt at the elbow and very sore. what could it be?

"tennis" elbow...: …especially if it hurts to turn her hand over against force like opening a door or picking up a frying pain. If it hurts in the other direction, it's "golfer's" elbow. You don't have to play these sports to get a sore elbow. You just have to strain your forearm tendons because they are anchored on your elbow. Try Ice, Ibuprofen, a tennis elbow band.See MD if not gone in 3 weeks or red/swollen