One of the main reasons bodybuilders experience persistent and often chronic wrist and elbow pain during pull-ups is improper alignment of the joints. That basically means that your elbow, wrist and shoulders are not in optimal position to take the load during the exercise. This causes larger stress on the connective tissue (ligaments and tendons) and can be the reason for injuries and chronic pain. One of the ways to fix that would be to do ring pull-ups instead of the regular straight bar version. However, if you don’t have access to rings or similar apparatus you can try another technique – the thumbless grip.
The thumbless grip basically means that when you grip the bar your thumb stays on the side of your fingers instead of wrapping around the bar and opposing to the other four fingers of the hand. This may seem like a minor tweak but it can really relief wrist pain during pull-ups since your wrists are put in proper alignment. If your wrist are straight, that has effect on your elbows and shoulders as well. On the other hand if you were to grab the bar with the thumb opposing, you will notice that your wrist sort of tilts to one side during the pull-up. This equals improper joint alignment and can be the cause of your feel pain.
Note: NEVER use the thumbless grip on exercises such as the bench press. It’s very dangerous and one wrong movement can cost your life. Always wrap your thumb around the barbell when performing the bench press.