Posterior shoulder dislocation occurs when the top of the upper arm bone, known as the humerus, moves backward out of its socket. This causes pain, muscle spasms, and a limited range of motion. The ...

OAKLAND, CA - MAY 26: Derek Jeter #2 of the New York Yankees hits a single that scored Eric Chavez #12 in the third inning against the Oakland Athletics at O.co Coliseum on May 26, 2012 in Oakland, ...

Upper back pain between the shoulder blades may result from poor posture or muscle strain. However, it can also stem from more serious problems with the spine, such as scoliosis or osteoarthritis.