Scapulohumeral Rythm

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Overview

2:1 overall

total ROM is 180 degrees (120 from GH and 60 from scapula)

maintain glenoid fossa in optimal position during ROM

maintain length-tension relationship

Phases

Setting: scapula shifts to stabilize humerus

occurs in first 30 degrees of abduction and 60 degrees of flexion

seen as mild scapular oscillation

after this it is 2:1

Setting to 90 degrees: upward rotary force started by scapular upward rotation

costoclavicular ligament tightness prevents AC movement

force is transmitted to SC (clavicle elevates)

scapular UR 30 degrees, elevation of clavicle stopped by costoclavicular ligament

90 degrees to full elevation

clavicle can't elevate due to costoclavicular lig tightness

continued force causes UR of clavicle

UR allows increase of 30 degrees of scapular rotation via trap and serratus

additional 60 degrees of GH (totalling 120 degrees)

may see 0-20 degrees of tipping and 0-40 degrees of winging at SC as scapula settles on rib cage