Bones and Joints of the Upper Limb

Bones and Joints of the Upper Limb

Shoulder Girdle

The shoulder girdle consists of the clavicle and scapula. The clavicle articulates medially with the sternum (sternoclavicular joint, saddle synovial — only bony attachment of upper limb to axial skeleton) and laterally with the acromion (acromioclavicular joint, plane synovial, stabilised by coracoclavicular ligament = conoid + trapezoid components). Clavicle fractures most commonly occur at the junction of the middle and lateral thirds, between the costoclavicular ligament (medial anchor) and coracoclavicular ligament (lateral anchor).

Glenohumeral (Shoulder) Joint

The glenohumeral joint is a multiaxial ball-and-socket joint between the spherical humeral head and the shallow glenoid cavity of the scapula. The glenoid labrum (fibrocartilage) deepens the cavity. The joint capsule attaches to the glenoid rim proximally and to the anatomical neck of the humerus, but extends inferiorly to the surgical neck — creating a lax inferior recess. This laxity allows wide range of motion but predisposes to anterior-inferior dislocation (most common direction; axillary nerve and anterior circumflex humeral artery at risk). The coracoacromial arch (coracoid + acromion + coracoacromial ligament) forms a roof over the joint, relevant in subacromial impingement. The rotator cuff (SITS: Supraspinatus, Infraspinatus, Teres minor, Subscapularis) blends with the capsule and dynamically stabilises the joint.

Elbow Joint

The elbow is a compound hinge joint with three articulations sharing one synovial cavity: humeroulnar (primary hinge, trochlea–trochlear notch), humeroradial (capitulum–radial head), and proximal radioulnar (pivot, radial head–radial notch of ulna). The ulnar (medial) collateral ligament (UCL, three bands) and radial (lateral) collateral ligament (RCL) stabilise against valgus and varus stress respectively. The annular ligament encircles the radial head, holding it against the ulna. Nursemaid's elbow (pulled elbow): radial head subluxation from the annular ligament in young children.

Forearm and Wrist

The proximal and distal radioulnar joints (both pivot synovial) allow pronation and supination; the interosseous membrane holds the radius and ulna together. The triangular articular disc at the distal radioulnar joint separates the joint from the wrist. The wrist (radiocarpal) joint is ellipsoidal (condyloid) between the distal radius + articular disc and the proximal row of carpals (scaphoid, lunate, triquetrum). Scaphoid fractures are common (fall on outstretched hand) and risk avascular necrosis (blood supply enters distally, supplying the proximal pole retrogradely).

Hand Joints

Carpometacarpal (CMC) joints 2–5 are plane synovial; the CMC of the thumb is saddle (most mobile, allows opposition). Metacarpophalangeal (MCP) joints are ellipsoidal; interphalangeal (IP) joints are hinge.