Shoulder Impingement/Rotator Cuff Tendinitis Shoulder anatomy Shoulder. A ball-and-socket joint made up of three bones: The humerus (upper arm bone) The scapula (shoulder blade) The clavicle (collarbone) Muscles and tendons. Form a covering around the head of the humerus and attach it to the shoulder blade, allowing the range of motion in your arm. Rotator… Continue reading Shoulder Impingement/Rotator Cuff Tendinitis