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 articulation of the radius with the ulna is effected by ligaments, which connect together both extremities as well as the centre of these bones. They may, consequently, be subdivided into three sets:
1. The superior radio-ulnar. 2. The middle radio-ulnar. 3. The inferior radio-ulnar articulations. This articulation is a lateral ginglymoid joint. The bones entering into its formation are the inner side of the circumference of the head of the radius, which is received into the lesser sigmoid cavity of the ulna. These surfaces are covered with cartilage, and invested with a duplicature of synovial membrane, continuous with that which lines the elbow-joint. Its only ligament ia The Orbicular Ligament(&g. 116) is a strong flat band of ligamentous fibres, which surrounds the head of the radius, and retains it in firm connection with the lesser sigmoid cavity of the ulna. It forms about three-fourths of a fibrous ring, attached by each end to the extremities of this cavity, and is broader at the upper part of its circumference than below, which serves to hold the head of the radius more securely in its position. Its outer surface is strengthened by the external lateral ligament, and affords partial origin to the Supinator brevis muscle. Its internal surface is smooth, and lined by the synovial membrane of the elbow-joint. Actions. The movement which takes place in this articulation is limited to rotation of the inner part of the head of the radius within the orbicular ligament, and upon the lesser sigmoid cavity of the ulna; rotation forwards being called prona-tion; rotation backward, supination. The interval between the radius and ulna in the middle of the forearm is occupied by two ligaments. - Oblique; - Interosseous. The Oblique or Sound Ligament (fig. 115) is a small round fibrous cord, which extends obliquely downwards and outwards, from the tubercle of the ulna at the base of the coronoid process, to the radius a little below the bicipital tuberosity. Its fibres run in the opposite direction to those of the interosseous ligament; and it appears to be placed as a substitute for it in the upper part of the interosseous interval. The Interosseous Ligament is a broad and thin plane of aponeurotic fibres, descending obliquely downwards and inwards, from the interosseous ridge on the radius to that on the ulna. It is deficient above, commencing about an inch beneath the tubercle of the radius; broader in the middle than at either extremity; and presents an oval aperture just above its lower margin for the passage of the anterior interosseous vessels to the back of the forearm. This ligament serves to connect the bones, and to increase the extent of surface for the attachment of the deep muscles. Between its upper border and the oblique ligament an interval exists, through which the posterior interosseous vessels pass. Two or three fibrous bands are occasionally found on the posterior surface of this membrane, which descend obliquely from the ulna towards the radius, and which have consequently a direction contrary to that of the other fibres. It is in relation, in front, by its upper three-fourths (radial margin) with the Flexor longus pollicis (ulnar margin), with the Flexor profundus digitorum (lying upon the interval between which are the anterior interosseous vessels and nerve), by its lower fourth with the Pronator quadratus; behind, with the Supinator brevis, Extensor ossis metacarpi pollicis, Extensor primi internodii pollicis, Extensor secundi internodii pollicis, Extensor indicis; and, near the wrist, with the anterior interosseous artery and posterior interosseous nerve. This is a lateral ginglymoid joint, formed by the head of the ulna being received into the sigmoid cavity at the inner side of the lower end of the radius. The articular surfaces are invested by a thin layer of cartilage, and connected together by the following ligaments. - Anterior radio-ulnar; - Posterior radio-ulnar; - Triangular Inter-articular Fibro-cartilage; - Synovial Membrane. The Anterior Radio-ulnar Ligament (fig. 117) is a narrow band of fibres, extending from the anterior margin of the sigmoid cavity of the radius to the anterior surface of the head of the ulna. The Posterior Radio-ulnar Ligament (ug. 118) extends between the same points on the posterior surface of the articulation. The Inter-articular Fibro-cartilage (fig. 119) is a thick fibro-cartilaginous lamella, of a triangular form, placed transversely, completing the wrist-joint, and binding the lower ends of the radius and ulna firmly together. Its circumference is more dense than its centre, which is thin and occasionally perforated; and it is thinner and broader externally than internally. It is attached by its apex to a depression which separates the styloid process of the ulna from the head of that bone; by its base, which is thin, to the prominent edge of the radius, which separates the gigmoid cavity from the carpal articulating surface, and by its anterior and posterior margins to the ligaments of the radio-carpal articulation. Its upper surface, smooth and concave, is contiguous with the head of the ulna; its under surface, also concave and smooth, with the cuneiform bone. Both surfaces are lined by a synovial membrane: the superior surface, by one peculiar to the radio-ulnar articulation; the inferior surface, by the synovial membrane of the wrist. The Synovial Membrane of this articulation has been called, from its extreme looseness, the membrana sacciformis; it covers the articular surface of the head of the ulna, and where reflected from this bone on to the radius, forms a very loose cul-de-sac; from the radius it is continued over the upper surface of the fibro-cartilage. The quantity of synovia which it contains is usually considerable. When the fibro-cartilage is perforated, this synovial membrane is continuous with that which lines the wrist-joint. Actions. The movement which occurs in the inferior radio-ulnar articulation is just the inverse of that which takes place between the two bones above; it is limited to rotation of the radius around the head of the nlna; rotation forwards being termed pronation, rotation backwards supination. In pronation, the sigmoid cavity glides forward on the articular edge of the ulna; in supination, it rolls in the opposite direction, the extent of these movements being limited by the anterior and posterior ligaments. |