The distal radioulnar joint is a pivot joint between the head of the ulna and the ulnar notch of the radius. Mechanically linked to the superior radioulnar joint, it is responsible for the movements of pronation (85°) and supination (90°).

A triangular fibrocartilaginous articular disc closes the distal radioulnar joint inferiorly and is the main structure uniting the radius and ulna (Palastanga et al 2006). It lies in a horizontal plane, its apex attaching to the ulnar styloid and its base to the lower edge of the ulnar notch of the radius. The disc articulates with the lunate when the hand is in ulnar deviation. It adds to the stability of the joint and acts as an articular cushion for the ulnar side of the carpus, absorbing compression, traction and shearing forces but being prone to degenerative changes (Livengood 1992, Rettig 1994, Wright et al 1994, Steinberg & Plancher 1995).

The movements of pronation and supination rotate the radius around the ulna. Supination is stronger, hence the thread of nuts and screws which are tightened by supination in right-handed people.

There are two rows of carpal bones; on the palmar aspect, from the radial to the ulnar side they are:

The carpal bones all articulate with their neighbours, except pisiform, which is a separate bone situated on the front of the triquetral. The intercarpal joints are all supported by intercarpal ligaments.

The wrist joint proper is a biaxial, ellipsoid joint between the distal end of the radius and the articular disc, and the proximal row of carpal bones. However, the so-called wrist joint complex includes the midcarpal joint and has mobility as well as stability, which is important for the function of the hand. Movements are extension (passive, 85°), flexion (passive, 85°), ulnar deviation (passive, 45°) and radial deviation (passive, 15°). The close packed position of the wrist joint is full extension.

The joints are surrounded by a fibrous capsule, lined with synovial membrane and reinforced by collateral ligaments. Both collateral ligaments pass from the appropriate styloid process to the carpal bones on the medial and lateral side of the carpus. A fibrocartilaginous meniscus projects into the joint from the ulnar collateral ligament.

The metacarpophalangeal joints are ellipsoid; the interphalangeal joints are hinge joints. Both are supported by palmar and collateral ligaments and the extensor tendons and digital expansions support the dorsal surfaces of the joints. Flexor tendons are contained within fibrous sheaths which have thickened areas known as pulleys which may provide a restriction, producing ‘trigger finger’ (see p. 175). At the wrist and in the hand, the tendons are contained within synovial sheaths (Standring 2009).

The flexor retinaculum, a strong fibrous band, creates a fibro-osseous passage, the carpal tunnel, through which pass the flexor tendons of the digits, the median nerve and vessels. The flexor retinaculum has four points of attachment: the pisiform and hook of hamate medially and the tuberosity of the scaphoid and ridge of trapezium laterally. Its attachment onto the trapezium splits to form a separate compartment for the tendon of flexor carpi radialis. The median nerve enters the carpal tunnel deep to palmaris longus. It shares its compartment of the carpal tunnel with nine tendons comprising the four tendons of flexor digitorum superficialis and the four tendons of flexor digitorum profundus, and flexor pollicis longus. On leaving the carpal tunnel it supplies the thenar muscles before dividing into four or five digital branches.

The trapeziofirst-metacarpal joint (first carpometacarpal joint) is a saddle joint with a loose articular capsule and extensive joint surfaces giving it a wide range of movement. The first metacarpal has been rotated medially for the movement of opposition.

Flexion and extension occur in a plane parallel to the palm of the hand, while abduction and adduction occur in a plane at right angles to the palm of the hand (Fig. 7.1 a–d).

The close packed position of the trapeziofirst-metacarpal joint is strong opposition, when great force is transmitted to the joint. The functionally opposed thumb is subjected to compressive stresses which make the joint vulnerable to degenerative osteoarthrosis.

The radial artery passes under abductor pollicis longus and extensor pollicis brevis, crossing the snuffbox obliquely towards the first dorsal interosseous muscle. Its position should be acknowledged so that it can be avoided when injecting the trapeziofirst-metacarpal joint.

Flexor carpi radialis (median nerve C6–C7) is the most lateral superficial flexor tendon. It passes through its own fibro-osseous compartment on the lateral side of the carpal tunnel, to insert into the base of the second and third metacarpals.

Palmaris longus (median nerve C7–C8) passes over, not under, the flexor retinaculum, to attach to the distal part of the flexor retinaculum and the palmar aponeurosis.

Flexor digitorum superficialis (median nerve C7–C8, T1) lies medial to palmaris longus, but is not as visible because it lies on a slightly deeper plane. In the carpal tunnel the four tendons are contained within the same synovial sheath, with tendons to the third and fourth fingers lying superficial to those to the second and fifth. The tendons divide to provide a passage for flexor digitorum profundus, before continuing on to insert either side of the middle phalanx.

Flexor carpi ulnaris (ulnar nerve C7–C8) is the most medial superficial flexor tendon and can be easily traced onto its insertion into pisiform. The tendon sends slips onwards as the pisohamate and pisofifth-metacarpal ligaments. The pisohamate ligament converts the space between pisiform and the hamate into a tunnel (tunnel of Guyon) for the passage of the ulnar vessels and nerves.

Abductor pollicis longus and extensor pollicis brevis (posterior interosseous nerve C7–C8) become tendinous and superficial in the lower forearm where they cross the tendons of extensor carpi radialis longus and brevis at the intersection point, a site of potential friction. They occupy the same synovial sheath in the first compartment of the extensor retinaculum and form the lateral border of the anatomical snuffbox. The abductor inserts into the base of the first metacarpal and the extensor into the base of the proximal phalanx. Because of its position, abductor pollicis longus has been considered both anatomically and functionally a radial deviator of the wrist (Elliott 1992a).

Look for three creases (not distinct in everyone) on the palmar aspect of the lower forearm. The distal wrist crease joins pisiform and the tubercle of the scaphoid, the bones at the heel of the hand (Backhouse & Hutchings 1990), marking the proximal border of the flexor retinaculum. The middle crease joins the two styloid processes, marking the position of the wrist joint line, while the proximal crease (if present) marks the proximal extent of the flexor tendon sheaths.

Consider the position of the bones which make up the two rows of carpal bones (Fig. 7.3). From the radial to the ulnar side, an easy way to remember the order is:

simply learn the parts	scaphoid, lunate, triquetral, pisiform
that the carpus has	trapezium, trapezoid, capitate, hamate

Joining the four points described above – pisiform, hook of hamate, tuberosity of scaphoid and ridge of trapezium – gives the position of the flexor retinaculum, which is approximately the size of your thumb when placed horizontally across the proximal palm (Fig. 7.2).

Identify the superficial forearm flexor tendons as they cross the palmar aspect of the wrist from the radial to ulnar side. Flexor carpi radialis is the most lateral tendon. Palmaris longus passes over the flexor retinaculum and can be brought into prominence by opposing the thumb and little finger with the wrist flexed. Flexor digitorum superficialis, lying in a deeper plane, may not be readily palpable, but flexor carpi ulnaris can be followed down to its insertion onto the pisiform.

Palpate for the radial pulse on the palmar aspect of the lower radius lateral to flexor carpi radialis. The ulnar pulse can be palpated on the lower ulna, lateral to flexor carpi ulnaris.

Consider the position of the median nerve as it enters the carpal tunnel deep to palmaris longus. If palmaris longus is absent, oppose the thumb and little finger and the midline crease produced gives the position of the median nerve.

Pronate the forearm and the head of the ulna can be seen as a rounded elevation in the distal forearm. Palpate to the ulnar side of the head and feel the tendon of extensor carpi ulnaris in the groove between the head of the ulna and the styloid process.

Palpate the inferior radioulnar joint line, which lies approximately 1.5 cm laterally from the ulnar styloid. Confirm its presence by passively gliding the head of the ulna on the radius and feeling the joint line.

On the lower end of the radius, palpate the dorsal tubercle (of Lister) lying roughly in line with the index finger. The tubercle is grooved on either side by the passing tendons. Extensor carpi radialis longus and brevis pass on its lateral side, while extensor pollicis longus passes on its medial side before taking a 45° turn laterally, where it can be traced to its insertion into the base of the distal phalanx of the thumb.

The capitate is the largest carpal bone and is roughly the size of the patient’s thumb nail. It is wider dorsally and is roughly peg-shaped. It is situated in the centre of the carpus, articulating mainly with the third metacarpal distally, the trapezoid laterally, the hamate medially and the concavity formed by the scaphoid and lunate proximally (Steinberg & Plancher 1995, Standring 2009). To locate the position of the capitate, run your finger proximally down the shaft of the third metacarpal with the wrist in slight flexion and drop over the end into the shallow depression.

Place the wrist in flexion with the thumb relaxed to allow the tendon of extensor pollicis longus to fall out of the way and to expose the base of the metacarpals. Now palpate the insertions of extensor carpi radialis longus and brevis onto the radial side of the base of the second and third metacarpals respectively. The extensor carpi radialis brevis is probably the easier of the two to feel. Palpate the insertion of extensor carpi ulnaris onto the medial side of the base of the fifth metacarpal.

Pronate the forearm and make a fist. The fleshy elevation seen at the distal end of the radius is formed by the musculotendinous junctions of abductor pollicis longus and extensor pollicis brevis as they wind around the lower radius, crossing over the tendons of extensor carpi radialis longus and brevis at the intersection point.

Locate the anatomical snuffbox (by extending the thumb) which is bordered by the tendons of abductor pollicis longus and extensor pollicis brevis laterally and by extensor pollicis longus medially. Palpate the radial styloid at the proximal end of the anatomical snuffbox and the trapeziofirst-metacarpal joint at the distal end.

Locate the tendons of abductor pollicis longus and extensor pollicis brevis; sometimes a V-shaped gap may be appreciated between the two.

The site of pain is usually well localized by the patient, with little spread, since these are peripheral joints and structures lying at the end of their respective dermatomes, with little scope for reference. The presence of paraesthesia or any apparent reference of pain may suggest a more proximal lesion, and all proximal joints must be examined, including the cervical spine. A fractured scaphoid gives localized pain and point tenderness in the anatomical snuffbox, while X-ray investigation may not show evidence of the fracture for several weeks (Livengood 1992).

The onset of the symptoms may be due to trauma, overuse or arthritis. If the onset is traumatic in nature, the possibility of fracture should be eliminated. Frequently, a direct injury involving a fall on the outstretched hand may cause fracture of the scaphoid or subluxation of the capitate or lunate bones, and may also cause a traumatic arthritis with soft tissue swelling and contusion. Indirect injury may also occur from a rotational force or maximal effort in racquet sports (Rettig 1994).

Most injuries at the wrist and hand develop from repetitive overuse. Tendinopathy may result from frequent overstretching or unaccustomed activity. An overuse syndrome occurs when the level of repeated microtrauma exceeds the tissue’s ability to adapt (Rettig 1994). Tensional overload or abnormal shear stresses can cause microtrauma at any point in the musculotendinous or ligamentous unit. The syndromes of carpal tunnel and de Quervain’s (see p. 171 & 174) may be associated with more proximal lesions, such as nerve entrapment or lesions of the cervical spine.

A hyperextension injury to the thumb is a relatively common sporting injury, producing a traumatic arthritis in either the trapeziofirst-metacarpal joint or the metacarpophalangeal joint. This may occur in skiing (‘skier’s thumb’) or sports which involve ball-catching, e.g. volleyball, netball or goal-keeping in football.

Swelling indicates active inflammation and the wrist may be fixed in the mid-position due to the presence of a joint effusion. Contusions with swelling are due to direct trauma. Excessive friction of the skin causes callus and blister formation, e.g. rowing and gymnastics. Ganglia are mucus-filled cysts, which are commonly seen around the wrist, particularly on the dorsum of the hand. They are common between the second and fourth decades of life (Smith & Wernick 1994) and if symptomatic may be burst or require surgical excision. Rheumatoid nodules may be present.

Since these are peripheral joints, palpation for signs of activity is conducted. Temperature changes are assessed and heat indicates an active inflammation, while cold may indicate circulatory problems (Fig. 7.6). It may be appropriate to palpate the ulnar and/or radial pulse (Fig. 7.7). Synovial thickening is usually palpated on the dorsum of the wrist (Fig. 7.8). Swelling is usually observed around the wrist where it may be fusiform, unilateral or bilateral. Other swellings, such as nodules or ganglia, can be palpated to assess whether they are hard or soft.

Before any movements are performed, the state at rest is esta-blished to provide a baseline for subsequent comparison.

The suggested sequence for the objective examination will now be given, followed by a commentary including the reasoning in performing the movements and the significance of the possible findings. Comparison should always be made with the other side.