Glenohumeral (GH) joint

  • is a ball & socket synovial joint with 3 rotary and 3 translatory degrees of freedom.
  • it has a capsule n associated lig n bursae
  • the articulation is composed of the large head of the humerus and smaller glenoid fossa
  • because the glenoid fossa of the scapula is the proximal segment of the glenohumeral joint, any motions of the scapula will influence glenohumeral function.
  • the glenohumeral joint has sacrificed articular congruency to incr the mobility of the upper extremity and hand
  • and is therefore susceptible to degenerative changes, instability & derangement

Articlular surfaces

The most lateral joint articulation of the shoulder
complex

The large head (ball) of the humerus bone articulates with the very shallow glenoid fossa (socket) of the scapula

The concavity of the glenoid fossa is increased by the articular cartilage (thin in the middle and thicker on the periphery)

Very congruent joint

The articular surface of humeral head is larger than that of the glenoid fossa

In anatomical position

  • Head will face medially, superiorly and posterior to the shaft and condyles of the humerus

Glenoid Labrum

  • Enhances the articular surface of the glenoid fossa
  • Attached to the periphery of the glenoid fossa
  • Increases concavity by 50%
  • A fibrocartilagenous ring
  • Functions include
  • Resistance to humeral head translations
  • Protection of bony edges of the labrum
  • Reduction of joint friction
  • Dissipation of joint contact forces
  • Attachment site for
  • Glenohumeral ligament
  • Tendon of the long head of the biceps brachii

Capsules and ligaments

  • Static reinforcements by the ligaments
  • Capsular Ligaments:
  • Coracohumeral Ligament (extracapsular)
  • A thin fibrous capsule that includes the superior,
    middle, and inferior glenohumeral ligaments.
  • This relatively loose capsule attaches between the rim of the glenoid fossa and the anatomic neck of the humerus
  • 2 bands: edge of the supraspinatus to greater tubercle and subscapularis to lesser tubercle
  • It helps limit the extremes of external rotation,
    flexion, and extension, as well as inferior displacement of the humeral head
  • Capsular surface area is twice the size of the humeral head
  • Dynamic reinforcement provided by the rotator cuff muscles and the tendons blend into the capsule

GH ligaments

GH ligaments at rest

Superior GH ligaments:

  • superior glenoid to the upper neck of humerus, deep to the coracohumeral ligament

Middle GH ligament:

Inferior GH ligament:

  • 3 components and some times
    referred to as a Inferior GH ligament complex (IGHLC),
    anterior, axillary, and posterior ligament bands
  • Each ligaments contributes differently to the GH stability

SGHL- Anterior and inferior joint stability by limiting
anterior and inferior translations of the humeral head when arm is at rest

  • the superior,middle and inferior glenohumeral ligaments are thickened regions within the capsule itself

the GHjoint is surrounded by a large, loose capsule that is
taut superiorly, n slack anteriorly & inferiorly with the arm dependent on the side,
the capsule tightenes when the humerus is abducted n laterally rotated, making this the closed packed position for GH joint.
capsular SA

GH lig at
45 degrees of Humeral Abduction
and
neutral rotation

MGHL
active

  • Anterior joint stability by limiting anterior humeral translations when arm is at rest
  • and upto 60 degrees of abduction
  • runs oblique from superior anterior
    labrum to anterior aspect of the proximal humerus below the superior GH ligament

at 90 degrees Humeral Abduction and
neutral rotation

IGHLC
active

Major role of stability
Resists inferior humeral head

90 degrees Humeral Abduction and
external rotation

IGHLC
active

active
Anterior band fans out to provide
anterior joint stability and
resistance to anterior humeral
head translation

90 degrees of Humeral Abduction and
medial rotation

IGHLC
active

Posterior band fans out to
provide posterior joint stability
and resistance to posterior
humeral head translation

Coracoacromial arch (suprahumeral arch)

Formed by the

  • Coracoid process - anteriorly
  • Acromion – posteriorly
  • Coracoacromial ligament – superiorly

Subacromial space:

the region between the arch
and humeral head

Contents of the subacromial space

  • Subacromial bursa
  • Rotator cuff tendons
  • Tendon of the long head of biceps brachii

function

Act as a barrier for superior translator forces

Bursae

2/both can also be considered as one

  • subacromial

located deep to the deltoid and acromion, and superficial to the supraspinatus tendon and joint capsule. The subacromial bursa reduces friction beneath the deltoid, promoting free motion of the rotator cuff tendons. Subacromial bursitis (i.e. inflammation of the bursa) can be a cause of shoulder pain.

  • subdeltoid

Separates the supraspinatus tendon and the head of the humerus from the acromion, coracoid process, Coracoacromial ligament and deltoid muscle.

Subacromial bursa and Subdeltiod bursa can be
separate or joined to form one Subacromial bursa

Reduces friction to permit smooth gliding between
humerus and the supraspinatus tendon and the
surrounding structures

Subacromial bursitis is a secondary problem to
inflammation of or degeneration of the supraspinatus tendon

Can decrease the subacromial space