Bones

  The radius The radius is a long bone in the forearm. It lies laterally and parallel to ulna, the second of the forearm bones. The radius pivots around the ulna to produce movement at the proximal and distal radio-ulnar joints. The radius articulates in four places: • Elbow joint – Partly formed by an articulation between the head of the radius, and the capitulum of the humerus. • Proximal radioulnar joint – An articulation between the radial head, and the radial notch of the ulna. • Wrist joint – An articulation between the distal end of the radius and the carpal bones. • Distal radioulnar joint – An articulation between the ulnar notch and the head of the ulna. Proximal Region of the Radius The proximal end of the radius articulates in both the elbow and proximal radioulnar joints. Important bony landmarks include the head, neck and radial tuberosity: • Head of radius – A disk shaped structure, with a concave articulating surface. It is thicker medially, where it takes ...

 The ulna The ulna is a long bone in the forearm. It lies medially and parallel to the radius, the second of the forearm bones. The ulna acts as the stabilising bone, with the radius pivoting to produce movement. Proximally, the ulna articulates with the humerus at the elbow joint. Distally, the ulna articulates with the radius, forming the distal radio-ulnar joint. Proximal Osteology and Articulation The proximal end of the ulna articulates with the trochlea of the humerus. To enable movement at the elbow joint, the ulna has a specialised structure, with bony prominences for muscle attachment. Important landmarks of the proximal ulna are the olecranon, coronoid process, trochlear notch, radial notch and the tuberosity of ulna: 1. Olecranon – a large projection of bone that extends proximally, forming part of trochlear notch. It can be palpated as the ‘tip’ of the elbow. The triceps brachii muscle attaches to its superior surface. 2. Coronoid process – this ridge of bone projec...

  The Humerus The humerus is a long bone of the upper limb, which extends from the shoulder to the elbow. The proximal aspect of the humerus articulates with the glenoid fossa of the scapula, forming the glenohumeral joint. Distally, at the elbow joint, the humerus articulates with the head of the radius and trochlear notch of the ulna. P roximal Landmarks The proximal humerus is marked by a head, anatomical neck, surgical neck, greater and lesser tuberosity and intertubercular sulcus. The upper end of the humerus consists of the head. This faces medially, upwards and backwards and is separated from the greater and lesser tuberosities by the anatomical neck. The greater tuberosity is located laterally on the humerus and has anterior and posterior surfaces. It serves as an attachment site for three of the rotator cuff muscles – supraspinatus, infraspinatus and teres minor – they attach to superior, middle and inferior facets (respectively) on the greater tuberosity. The lesser tuber...

  The clavicle  The clavicle (collarbone) extends between the manubrium of the sternum and the acromion of the scapula. It is classed as a long bone and can be palpated along its length. In thin individuals, it is visible under the skin. The clavicle has three main functions: • Attaches the upper limb to the trunk as part of the ‘ shoulder girdle’. • Protects the underlying neurovascular structures supplying the upper limb. • Transmits force from the upper limb to the axial skeleton. Bony Landmarks and Articulations The clavicle is a slender bone with an ‘S’ shape. Facing forward, the medial aspect is convex, and the lateral aspect concave. It can be divided into a sternal end, a shaft and an acromial end. Sternal (medial) End The sternal end contains a large facet – for articulation with the manubrium of the sternum at the sternoclavicular joint. The inferior surface of the sternal end is marked by a rough oval depression for the costoclavicular ligament (a ligament of the SC...

 The scapula The scapula is also known as the shoulder blade. It articulates with the humerus at the glenohumeral joint, and with the clavicle at the acromioclavicular joint. In doing so, the scapula connects the upper limb to the trunk. It is a triangular, flat bone, which serves as a site for attachment for many muscles. Costal Surface The costal (anterior) surface of the scapula faces the ribcage. It contains a large concave depression over most of its surface, known as the subscapular fossa. The subscapularis (rotator cuff muscle) originates from this fossa. Originating from the superolateral surface of the costal scapula is the coracoid process. It is a hook-like projection, which lies just underneath the clavicle. Three muscles attach to the coracoid process: the pectoralis minor, coracobrachialis, and the short head of the biceps brachii. Lateral Surface The lateral surface of the scapula faces the humerus. It is the site of the glenohumeral joint, and of various muscle at...