Beth Skwarecki is Lifehacker’s Senior Health Editor, and holds certifications as a personal trainer and weightlifting coach. She has been writing about health for over 10 years. Your shoulders are an ...

Your deltoid muscles make up a main muscle group in your upper body. They’re connected with many other muscles and bones in your upper back, neck, and shoulder region and are extremely mobile. They ...

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 ...