The subscapularis muscle is found on the inside of the shoulder blade. It can cause severe pain in the shoulder blade area that can also run down the back of the arm. Pain is also often felt in the wrist, but not the forearm.
The serratus anterior muscle can contribute to pain down the side of the ribs, around the shoulder blade, and may chest, arm, hand and fingers. It also contributes to pain in the back around the shoulder blade and down the side of the ribs.
The serratus posterior superior muscle is a muscle found in the upper back. It contributes to pain in shoulder, shoulder blade region, arm, hand and little finger. It can also contribute to pain in the upper chest.
The brachialis muscle connects the upper arm to the lower arm. It contributes to pain in the upper arm, elbow, thumb pad and thumb. It can also cause tingling and / or numbness in the back of the forearm into the thumb. Bending and straightening the elbow is painful.