Labral (Pathologic) Similarities for the Human Shoulder and Hip JointThomas Berendes
Large differences exist between two- and four-legged locomotion, major morphological changes occurred in the human musculoskeletal system to facilitate its new purpose. The shoulder (glenohumeral) joints’ primary purpose shifted from stability to increase mobility. Contradictory, the hip (acetabulofemoral) joints’ primary purpose shifted from mobility to increase stability. However, stability and mobility are opposing functions and an optimal new equilibrium needed to be generated by means of morphological changes. These morphological changes had a noticeable effect on the shoulder and hip joints. The shoulder and hip joints are the largest balland socket joint in the human body and etiologically they possess, next to distinct differences, also many similarities. Both joints are assisted through static and dynamic stabilizers. The static stabilizers include the bony anatomy, the labrum, the joint capsule and the ligaments. The dynamic stabilizers are the surrounding muscles. Together the static and dynamic stabilizers form a perfect morphological compromise between mobility and stability. However, this perfect compromise differs for the shoulder and hip as their specific demands differ.