What is the main function of the shoulder?
To position and stabilize the arm in space
Is the shoulder mainly made for mobility or stability?
Mobility!
What are the 4 distinct anatomic articulations at the shoulder? Are there any biomechanical articulations?
-Glenohumeral
-Sternoclavicular
-Acromioclavicular
-Scapulothoracic
-Coraco-acromial arch
-Upper thoracic spine
What are the cardinal motions that occur at the shoulder joint?
-Flexion/extension
-Abduction/adduction
-Internal/external rotation
-Horizontal abduction/adduction
What type of joint is the glenohumeral joint? How is it different from the hip joint?
-Ball and socket
-It is much shallower than the hip joint to allow for more mobility
What provides structural stability to the shoulder?
-Glenoid labrum
-Joint capsule
-GH ligaments
-Rotator cuff muscles
What are the arthrokinematics occuring at the GH joint?
-It is a convex (humerus) on concave (glenoid fossa)
-The joint must roll and glide in opposite directions, so when the humerus moves upward, the humeral head glides downwards
What are the cardinal motions of the scapula?
-Retraction/protraction
-Elevation/depression
-Upward rotation
What combined motions must occur in order to do elevation (scaption)?
-About 30 degrees of abduction
-Slight shoulder external rotation
-1/3 of elevation comes from the scapulothoracic joint
-2/3 from GH joint
What are the component motions of the clavicle?
-Elevation/depression
-Protraction/retraction
-Rotation on the medial and lateral axis
What are the two active shoulder mobility functional tests and what do they measure?
-Scratch tests (behind the back and behind the neck)
-Behind the back is extension and internal rotation
-Behind the neck is flexion and external rotation
What is the ligamentous support at the shoulder?
-GH has anterior GH ligaments
-Acromioclavicular (AC) ligament
-Coraco-acromial ligament
What are the anterior GH ligaments? When are they tight?
-Superior: tight when arm is at side
-Middle: tight when arm is at 45 degrees of elevation (flexion or abduction)
-Inferior: tight when arm is above 90 degrees of elevation
What are the two coraco-clavicular ligaments?
-Conoid
-Trapezoid
What ligaments tear during acromioclavicular joint dislocation?
The AC ligaments tear as well as the coracoclavicular ligaments
What are the four main muscle groups at the shoulder?
-Rotator cuff/protectors (SITS)
-Scapular positioners
-GH “power” muscles
-Upper extremity propellers
What are the four rotator cuff muscles?
-Supraspinatus
-Infraspinatus
-Teres minor
-Subscapularis
What are the scapular positioner muscles?
-Upper, middle, and lower trap
-Rhomboids
-Pec minor
-Serratus anterior
What is the power muscle at the shoulder?
Deltoid
What are the propeller muscles of the shoulder/humerus?
Pec major and latissimus dorsi
What structures make up the subacromial arch?
-Coracoid process to acromion process
-Coracoacromial ligament
What passes under the subacromial (coracoacromial) arch?
-Sub-deltoid bursa
-Tendons of the rotator cuff and long head of biceps tendon
-Bony aspects of the head of the humerus
What causes subacromial impingement?
-When the subacromial space narrows which can be caused by bursitis or inflammed tendons
-It can also be caused if the end of someone’s clavicle is curved downward
What is the purpose of the elbow, forearm, and wrist?
To position the hand in space