This document summarizes static and dynamic mechanisms of shoulder stability. It discusses how the glenohumeral joint has little inherent bony stability and relies on ligaments, joint pressure, capsule adhesion, and rotator cuff muscles. Statically, the shoulder is stabilized by negative intra-articular pressure and upward scapular rotation. Dynamically, the deltoid and rotator cuff centering the humeral head compress the joint surfaces and increase dynamic ligament tension during arm movement. Damage to one side of the joint can increase translation risk and potential injury to the opposite side.

1. Statis dan Gerakan pada Aktivitas
Sehari - hari
Mahasiswa :
Abdillah Budi Ksatria - 211231007
Pembimbing :
Prof. Viskasari P. Kalanjati, dr., M.Kes., PA(K)., PhD

2. Shoulder stability concept.
●Static mechanism:
Bony
Ligamentous
Joint pressure/volumes
GHJ has a very lil inherent bony stability. Normally
translation of humeral head is 50% anterior and so as postr,
and must nt exceed the 6mm transltn from the COR during
shoulder motion.
Humeroscapular stability=Concave on convex
Scapulohumeral stability= Convex on concave.

3. Static Stabilization of the GH Joint : UNLOADED
ARM
• PASSIVE TENSION IN THE ROTATOR INTERVAL CAPSULE
• AIR-TIGHT CAPSULE PRODUCING NEGATIVE INTRAARTICULAR
PRESSURE
• GLENOID INCLINATION-THERE IS SLIGHT UPWARD TILT OF GLENOID
FOSSA EITHER DUE TO ANATOMICALLY OR DUE TO UPWARD
ROTATION OF THE SCAPULA.

4. ●Joint pressure and volume acting as static stabliser to
GHJ:
Negative atmospheric pressure contributes to shoulder
stabiilty.
Adhesion/cohension: joint surface stick together; allowing
motion but not separation.
Limited joint volume contribute to shoulder stability.
(pathological example= adhesive capsulitis, where joint
volume is reduced leading to hypomobility).

5. UNLOADED ARM

6. DYNAMIC STABILIZATION OF THE GH JOINT
• The Deltoid and Glenohumeral Stabilization
• The majority of the force of contraction of the deltoid causes the
humerus and humeral head to translate superiorly; only a small
proportion of force is applied perpendicular to the humerus and
directly contributes to rotation (abduction) of the humerus.
• It also produces a shear force rather than a compressive force
• The deltoid cannot independently abduct (elevate) the arm.
Another force or set of forces must be introduced to work
synergistically with the deltoid for the deltoid to work effectively.

7. LOADED ARM-STATIC STABILIZATION
• SUPRASPINATUS
ACTIVITY STARTS
WHEN THE PASSIVE
TENSION IN ROTATOR
INTERVAL CAPSULE IS
INSUFFICIENT AS IN
LOADED ARM.

8. The Rotator Cuff and Glenohumeral
Stabilization
• ROTATOR OR MUSCULOTENDINOUS CUFF MUSCLES ARE:
1) Supraspinatus (S)
2) Infraspinatus (I)
3) Teres minor(T)
4) Subscapularis(S)

9. Dynamic shoulder stability
Rotator Cuff:Active contraction of these muscles centers
the GH articulation, and compressess the joint surfaces.
Force couples:
Scapular
Humeral
Neuromuscular Control and function: Increases dynamic
ligament tension.

10. Circle concept of instability
● If one side of the joint is damaged in the GHJ, there is high chances of the
opposite getting damaged reason being humeral head slides away the
opposite direction hitting the structure on the opposite side, that is
increased translation is possible with injury to one side of the joint, whereas
dislocation requires injury to the opposite as well.

11. • McDonald, A. C., Savoie, S. M., Mulla, D. M., & Keir, P. J.
(2018). Dynamic and static shoulder strength relationship and
predictive model. Applied Ergonomics, 67, 162-169.
• Imai, T., Nagamatsu, T., Kawakami, J., Karasuyama, M.,
Harada, N., Kudo, Y., & Madokoro, K. (2023). Effects of
elevation on shoulder joint motion: comparison of dynamic and
static conditions. Clinics in Shoulder and Elbow, 26(2), 148.