A strong ligament called the flexor retinaculum spans the top of this U-shaped area to maintain this grouping of the carpal bones.
Such breaks often occur because of the force exerted on the clavicle when a person falls onto his or her outstretched arm, or when the lateral shoulder receives a strong blow.
These provide attachments for muscles of the arm.
The hypothenar muscles are on the medial aspect of the palm, and the intermediate muscles are midpalmar.
Named for their locations, the supraspinatus superior to the spine of the scapula and the infraspinatus inferior to the spine of the scapula abduct the arm and laterally rotate the arm, respectively.
When the scapula is moved medially it lies in a frontal plane with the glenoid cavity facing directly laterally.