The Shoulder Complex
Hey bloggers!
Today I'm going to talk about the shoulder complex in kinematics. The clavicle, scapula, and humerus function together as a kinetic chain to produce functional upper extremity movement. Each joint contributes to the total motion, so a much larger range of motion is produced than if each joint worked individually.
During shoulder abduction (overhead elevation of the arm), there is a relationship of movement that exists between the humerus and the scapula. The collaborative movement between the humerus and the scapula is referred to as the scapulohumeral rhythm. This movement is achieved when, beyond 30 degrees of abduction or 60 degrees of flexion (little scapular movement), for every 3 degrees of shoulder elevation, 2 degrees occurs at the glenohumeral (GH) joint and 1 degree results from the scapulothoracic (ST) joint upward rotation. The amount of humeral movement maintains a ratio of movement with the scapula of 2:1. Therefore, a full 180 degrees of motion during arm elevation results from 120 degrees of GH joint movement and 60 degrees of ST upward rotation.
The scapula's upward rotational movement allows many things to occur: 1) its changing position allows the scapular glenoid fossa to maintain alignment with the head of the humerus; 2) the shoulder abductor muscles are able to maintain an optimal length-tension relationship; 3) middle deltoid and supraspinatus muscles are able to successfully move the humerus through great ROM; and 4) subacromial space is maintained. If the scapula's upward rotational movement does not occur successfully, there will be a reduction in subacromial space and as a result, injure structures such as the supraspinatus muscle tendon.
The movement between the humerus and the scapula must be synchronous; and in order for this to be successful, optimal congruency must be maintained between the glenoid fossa and the humeral head.
For full range, the humeral head must rotate laterally in order for the greater tubercle to pass by the acromion without impingement of structures within the subacromial space.
Well, that's all for today guys!
Always stay natural,
naturalOT
Sources:
Samuels, V. (2018). Foundation in kinesiology and biomechanics. Philadelphia: F.A. Davis Company.
Today I'm going to talk about the shoulder complex in kinematics. The clavicle, scapula, and humerus function together as a kinetic chain to produce functional upper extremity movement. Each joint contributes to the total motion, so a much larger range of motion is produced than if each joint worked individually.
During shoulder abduction (overhead elevation of the arm), there is a relationship of movement that exists between the humerus and the scapula. The collaborative movement between the humerus and the scapula is referred to as the scapulohumeral rhythm. This movement is achieved when, beyond 30 degrees of abduction or 60 degrees of flexion (little scapular movement), for every 3 degrees of shoulder elevation, 2 degrees occurs at the glenohumeral (GH) joint and 1 degree results from the scapulothoracic (ST) joint upward rotation. The amount of humeral movement maintains a ratio of movement with the scapula of 2:1. Therefore, a full 180 degrees of motion during arm elevation results from 120 degrees of GH joint movement and 60 degrees of ST upward rotation.
The scapula's upward rotational movement allows many things to occur: 1) its changing position allows the scapular glenoid fossa to maintain alignment with the head of the humerus; 2) the shoulder abductor muscles are able to maintain an optimal length-tension relationship; 3) middle deltoid and supraspinatus muscles are able to successfully move the humerus through great ROM; and 4) subacromial space is maintained. If the scapula's upward rotational movement does not occur successfully, there will be a reduction in subacromial space and as a result, injure structures such as the supraspinatus muscle tendon.
The movement between the humerus and the scapula must be synchronous; and in order for this to be successful, optimal congruency must be maintained between the glenoid fossa and the humeral head.
For full range, the humeral head must rotate laterally in order for the greater tubercle to pass by the acromion without impingement of structures within the subacromial space.
Well, that's all for today guys!
Always stay natural,
naturalOT
Sources:
Samuels, V. (2018). Foundation in kinesiology and biomechanics. Philadelphia: F.A. Davis Company.
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