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1. STATIC STABILITY OF SHOULDER
JOINT 22-09-2020
DR HARI BABU. K. V
PRINCIPAL
P.P.SAVANI SCHOOL OF PHYSIOTHERAPY

2. Static stability is provided by
1. Passive tension in rotator interval Capsule
(superior capsule, Superior GH ligament and
Coraco humeral ligament)
2. Negative intra articular pressure
3. Degree of glenoid inclination provided by
scapulo thoracic posture.

3. 1. Passive tension in rotator capsule interval
• GH is having incongruent articular surfaces
• More stability and less stability
• As the humeral head rests on the fossa,
gravity acts on the humerus parallel to the
shaft in a downward direction
• This appears to require a vertical upward pull
to maintain equilibrium

4. • Such a vertical force could be supplied by
muscles such as the deltoid, supraspinatus, or
the long heads of the biceps brachii and
triceps brachii.
• Studies shows that all muscles of the shoulder
complex are electrically silent in the relaxed,
unloaded limb and even when the limb is
tugged vigorously downward

5. • The mechanism of joint stabilization,
therefore, appears to be passive.
• The line of gravity (LoG) acting on the upper
extremity (and extended through the
humerus) creates a downward force on the
humerus

6. • Given the magnitude of passive tension in the
structures of the rotator interval capsule (RIC)
(superior capsular ligament, coracohumeral
ligament and tendon of supraspinatus) that
are taut when the arm is at the side.
• The resultant pull of both the LoG and the
rotator interval capsule creates a line of force
that compresses the humeral head into the
lower portion of the glenoid fossa

7. 2.Negative intra-articular pressure.
• This pressure creates a relative vacuum that
resists inferior humeral translation caused by
the force of gravity
• Venting the capsule or tears in the glenoid
labrum, results in large increases in inferior
humeral translations.
• If available passive forces are inadequate for
static stabilization activity of supraspinatus is
required( Load in hand)

8. • Supraspinatus has attachment to rotator
interval capsule
• Supraspinatus is not active during arms by the
side
• Paralysis or dysfunction of supraspinatus may
lead to gradual inferior subluxation ofGH joint
• Without reinforcing passive tension of intact
supraspinatus load on RIC gradually stretch an
(Rotator interval capsule) results in loss of
joint stability

9. 3.Degree of Glenoid inclination
• Degree of glenoid inclination influences the
stability of the GH joint with the arm in the
dependent position

10. Stabilizers and Mobilizers
• The proximal stabilizers are muscles that
originate on the spine, ribs, and cranium and
insert on the scapula and clavicle. Examples of
these muscles are the serratus anterior and
the trapezius

11. • The distal mobilizers consist of muscles that
originate on the scapula and clavicle and
insert on the humerus or the forearm.
Examples of two distal mobilizers are the
deltoid and biceps brachii muscles

12. • optimal function of the shoulder complex
requires an interaction between the proximal
stabilizers and the distal mobilizers
• For example, for the deltoid to generate an
effective abduction torque at the
glenohumeral joint, the scapula must be firmly
stabilized against the thorax by the serratus
anterior and trapezius muscles

13. • In cases of a paralyzed serratus anterior
muscle, for example, the deltoid muscle is
unable to express its full abduction function

14. Scapulo thoracic posture
• Scapulothoracic posture maintains the glenoid
fossa slightly upwardly rotated
• Ideal posture of the shoulder girdle
incorporates a slightly elevated and relatively
retracted scapula, with the glenoid fossa
facing slightly upward

15. • The upper trapezius, by attaching to the
lateral end of the clavicle, provides excellent
leverage around the SC joint for maintenance
of this ideal posture
• A chronically downwardly rotated posture may
be associated with “poor posture” or may be
secondary to paralysis or weakness of certain
muscles, such as the upper trapezius

17. • loss of the upwardly rotated position increases
the angle between the force vectors created
by the superior capsular structures and gravity
• Adding the force vectors produced by the
superior capsular structures and gravity now
yields a reduced compressive force
• Gravity can pull the humerus down the face of
the glenoid fossa

18. • Over time, and if not supported by external
means, the downward pull can result in plastic
deformation of the superior capsular
structures.
• As a consequence, the inadequately
supported head of the humerus may
eventually sublux or dislocate inferiorly from
the glenoid fossa

19. • More generally, however, all the elevators of
the scapulothoracic joint may be weakened or
paralyzed after a stroke or from a disease such
as muscular dystrophy
• loss of muscular support of the shoulder girdle
allows gravity to be the dominant force in
determining the resting posture of the
scapulothoracic joint

20. • Such a posture typically includes a depressed,
protracted, and excessively downwardly
rotated scapula
• Over time this posture can produce damaging
stress on other structures located within the
shoulder region
• a depressed clavicle has resulted in superior
dislocation of the SC joint

21. • As the lateral end of the clavicle is lowered,
the medial end is forced upward because of
the fulcrum action of the underlying first rib.
• The depressed shaft of the clavicle may
compress the subclavian vessels and part of
the brachial plexus.

22. • Another consequence of long-term paralysis
of the upper trapezius is an inferior dislocation
(or subluxation) of the GH joint
• The downward pull imposed by gravity on an
unsupported arm may strain the capsular
ligaments at the GH joint and eventually lead
to an irreversible dislocation

23. • This complication is often observed in persons
with flaccid hemiplegia, which may
necessitate a sling for external support of the
arm.