Biomechanics Exam 3

Upper Trapezius Movements

PM elevation and upward rotation (overactive/tight)

Middle trapezius Movements

PM retraction

Lower Trapezius Movements

PM depression and upward rotation, assist retraction (underactive/weak)

Upward rotation: force coupling

upper traps pulls up and in, lower traps pull down, inferior angle of scapula pulls out.

Levator Scapulae Movement

PM elevation and downward rotation, Assist retraction

Rhomboids Major and Minor Movement

PM elevation, retraction, and downward rotation (underactive/weak-protracted shoulder girdle) Scapular stabilizer

Serratus Anterior Movement

PM protraction and upward rotation, assist depression. (weak/underactive- winged scapula)

Pectoralis Minor Movements

PM depression, protraction, and downward rotationof the scapula; assists in shoulder girdle stabilization. (overactive/tight-protraction)

Downward Rotation: Force Coupling

Rhomboids up and in, Levator Scapula up, pectoralis minor down.

Elevation Muscles

Rhomboids, Upper trapezius, Levator Scapulae

Depression Muscles

Lower Trapezius, Pectoralis Minor, Serratus anterior

Protraction Muscles

Pectoralis Minor, Serratus Anterior

Retraction Muscles

Rhomboids, Middle Trapezius, Lower Trapezius, Levator Scapulae

Upward Rotation Muscles

Serratus Anterior, Upper Trapezius, Lower Trapezius

Downward Rotation muscles

Rhomboids, Levator Scapulae, Pectoralis Minor

Glenohumeral Anatomy

Bones: scapula and humerus (ball and socket joint) Action: Flexion, extension, abduction, adduction, horizontal abduction, horizontal adduction, internal rotation, external rotation. Degrees of Freedom: 3 triaxial, Closed Pack position: 90 degrees of abduction and full external rotation.

Glenohumeral Joint Actions

Abduction, Adduction, Flexion, Extension, Internal Rotation, External Rotation, Horizontal Abduction, Horizontal Adduction

Glenohumeral Abduction is caused by scapular

upward rotation

Glenohumeral Adduction is caused by scapular

downward rotation

Glenohumeral Horizontal Abduction is caused by scapular

retraction

Glenohumeral Horizontal Adduction is caused by scapular

protraction

Glenohumeral Internal Rotation is caused by scapular

Protraction

Glenohumeral External Rotation is caused by scapular

retraction

Glenohumeral flexion is caused by scapular

upward rotation protraction

Glenohumeral extension is caused by scapular

downward rotation retraction

Normal ROM for glenohumeral flexion

180 degrees

Normal ROM for glenohumeral abduction

180 degrees

Normal ROM for glenohumeral internal rotation

Arm at 90 degrees, should get to70

Normal ROM for glenohumeral external rotation

Arm at 90 degrees, should be able to get to 90 degrees

Glenoid Labrum

The labrum is fibrocartilage that sits on the edge of the fossa and provides stability to the glenohumeral joint by deepening the socket, thereby increasing the surface area for contact with the humeral head. This will also help to reduce friction in between bones

Joint Capsule

The joint capsule is a fibrous tissue that surrounds the glenohumeral joint, providing stability and containing synovial fluid which lubricates the joint, allowing for smooth movement.

Muscles of the Glenohumeral Joint

Rotator Cuff, Pectoralis Major, Latissimus Dorsi, Deltoid, Biceps Brachii, Coracobrachialis, Teres Major, Triceps Brachii.

Infraspinatus Movement (SITS)

PM external rotation and stabilization, assist horizontal abduction

Teres Minor

PM external rotation and sabilization, assist horizontal abduction

Supraspinatus

PM abduction and stabilization

Subscapularis