Articulations
Synarthrosis, or immoveable
Amphiarthrosis, or mixed
Diarthrosis, or moveable
Kinds of movement
Articulations of the trunk
The vertebral column
The atlas with the axis
The atlas with the occiptal bone
The axis with the occiptal bone
Tempoko-maxillart articulation
The ribs with the vertebras
The cartilages of the ribs with the sternum
Ligaments of the sternum
The pelvis with the spine
The pelvis
Articulations of the upper extremity
Sterno-clavicular articulation
Scapulo-clavicular articulation
Proper ligaments of the scapula
Shoulder joint
Elbow joint
Radio-ulnar articulations
Whist joint
Articulations of the carpus
Capro metacapral articulations
Metacarpo-phalangeal articulations
Articulations of the phalanges
Articulations of the lower extremity
Hip joint
The knee joint
Articulations between the tibia and fibula
Ankle joint
Articulations of the tarsus
Tarso-metatarsal articulations
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The Shoulder is an enarthrodial or ball and socket joint. The bones entering into its formation are the large globular head of the humerus, which is received into the shallow glenoid cavity of the scapula, an arrangement which permits of very considerable movement, whilst the joint itself is protected against displacement by the strong ligaments and tendons which surround it, and above by an arched vault, formed by the under surf ace of the coracoid and acromion processes, and the coraco-acromion ligament. The two articular surfaces are covered by a layer of cartilage, which on the head of the humerus is thicker at the centre than at the circumference, the reverse being observed in the glenoid cavity. Its ligaments are the
- Capsular - Coraco-humeral - Glenoid - Synovial Membrane The Capsular Ligament completely encircles this articulation; being attached, above, to the circumference of the glenoid cavity beyond the glenoid ligament; below, to the margin of the neck of the humerus, approaching nearer to the articular cartilage above, than in the rest of its extent. It is thicker above than below, remarkably loose and lax, and much larger and longer than is necessary to keep the bones in contact, allowing them to be separated from each other more than an inch, an evident provision for that extreme freedom of movement which is peculiar to this articulation. Its external surface is strengthened above by the Supra spi-natus; above and internally by the coraco-humeral ligament; below, where it is thin and weak, the long tendon of the Triceps is separated from it by a little loose areolar tissue; externally the tendons of the Infra-spinatus and Teres minor are firmly attached to it; and internally, the tendon of the Sub-scapularis. The cap-sular ligament usually presents three openings; one at its inner side, partially filled up by the tendon of the Sub-scapularis; it establishes a communication between the synovial membrane of the joint, and a bursa beneath the tendon of that muscle; a second, not constant, at its external part, where a communication exists between the joint and a bursal sac belonging to the Infra-spinatus muscle. The third is seen in the lower border of the ligament, between the two tuberosities, for the passage of the tendon of the Biceps muscle. The Coraco-humeral or Accessory Ligament, is a broad band which strengthens the upper and inner part of the capsular ligament. It arises from the outer border of the coracoid process, and descends obliquely downwards and outwards to the anterior part of the great tuberosity of the humerus, being blended with the tendon of the Supra-spinatus muscle. This ligament is intimately united to the capsular in the greater part of its extent. 
The Glenoid Ligament is a fibro-cartilaginous band attached around the margin of the glenoid cavity. It is triangular on section, the thickest portion being fixed to the circumference of the cavity, the free edge being thin and sharp. It appears to be mainly formed of the fibres of the long tendon of the Biceps muscle, bifurcating at the upper part of the glenoid cavity into two fasciculi, which encircle its margin and unite at its lower part. This ligament deepens the cavity for articulation, and protects the edges ofthe bone. It is lined by the synovial membrane. The Synovial Membrane lines the glenoid cavity and the fibro-cartilaginous rim surrounding it; it is then reflected over the internal surface of the capsular ligament, lines the lower part and sides of the neck of the humerus, and is continued over the cartilage covering the head of this bone. The long tendon of the Biceps muscle which passes through the joint, is enclosed in a tubular sheath of synovial membrane, which is reflected upon it at the point where it perforates the capsule, and is continued around it as far as the summit of the glenoid cavity, where it is continuous with that portion of the membrane which covers its surface. The tendon of the Biceps is thus enabled to traverse the articulation, but is not contained in the interior of the synovial cavity. The synovial membrane communicates with a large bursal sac beneath the tendon of the Sub-scapularis, by an opening at the inner side of the capsular ligament; it also occasionally communicates with another bursal sac, beneath the tendon of the Infra-spinatus, through an orifice at its upper part. A third bursal sac, which does not communicate with the joint is placed between the under surface of the deltoid and the outer surface of the capsule. The Muscles in relation with this joint are, above, the Supra-spinatus; below, the long tendon of the Triceps; internally, the Sub-scapularis; externally, the Infra-spinatus and Teres minor; within, the long tendon of the Biceps. The Deltoid is placed most externally, and covers the articulation on its outer side, and in front and behind. The Arteries supplying this joint are articular branches of the anterior and posterior circumflex, and supra-scapular. Actions. The shoulder joint is capable of movement in almost any direction, forwards, backwards, abduction, adduction, circumduction, and rotation. |