What are the compartments of shoulder?

The shoulder is divided into several compartments, primarily including the anterior, posterior, and lateral compartments. The anterior compartment contains muscles such as the pectoralis major and biceps brachii, which are involved in flexion and adduction. The posterior compartment houses muscles like the supraspinatus and infraspinatus, responsible for shoulder stabilization and external rotation. The lateral compartment includes the deltoid muscle, which is key for arm abduction.