Shoulder injuries are common and are usually caused by sports-related injuries that are repetitive, impactful, jarring, or include over-head movement of the arms. Shoulder injuries can also be the result of a fall or other kinds of accidents. Stiffness, feeling like your shoulder could “pop out” of place or reduced strength are indications there might be something wrong.
Most shoulder problems involve the muscles, tendons, and ligaments, rather than bones and are due to injury.