Wrist Joint: Anatomy

Bones of the Wrist

The bones of the wrist consist of:

• Distal radius Radius The outer shorter of the two bones of the forearm, lying parallel to the ulna and partially revolving around it. Forearm: Anatomy and ulna Ulna The inner and longer bone of the forearm. Forearm: Anatomy: The distal ulna Ulna The inner and longer bone of the forearm. Forearm: Anatomy is not technically part of the wrist, as it articulates distally with the triangular fibrocartilage Fibrocartilage A type of cartilage whose matrix contains large bundles of collagen type I. Fibrocartilage is typically found in the intervertebral disk; pubic symphysis; tibial menisci; and articular discs in synovial joints. Cartilage: Histology complex (TFCC).
• 5 proximal metacarpals 
• 8 carpal bones, arranged in 2 rows:
  1. Proximal row (lateral to medial): scaphoid, lunate, triquetrum, and pisiform
  2. Distal row (lateral to medial): trapezium, trapezoid, capitate, and hamate

There are many mnemonics to help memorize the order and location of the carpal bones Carpal bones The eight bones of the wrist: scaphoid bone; lunate bone; triquetrum bone; pisiform bone; trapezium bone; trapezoid bone; capitate bone; and hamate bone. Carpal Tunnel Syndrome. They are learned from lateral to medial and proximal to distal: scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate.

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Joints of the Wrist

The wrist is able to move in multiple directions, as it functions as a stable platform for the hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy.

Movements of the Wrist and Associated Muscles

The wrist acts as a transition between the forearm Forearm The forearm is the region of the upper limb between the elbow and the wrist. The term “forearm” is used in anatomy to distinguish this area from the arm, a term that is commonly used to describe the entire upper limb. The forearm consists of 2 long bones (the radius and the ulna), the interosseous membrane, and multiple arteries, nerves, and muscles. Forearm: Anatomy and hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy. The table below summarizes the forearm Forearm The forearm is the region of the upper limb between the elbow and the wrist. The term “forearm” is used in anatomy to distinguish this area from the arm, a term that is commonly used to describe the entire upper limb. The forearm consists of 2 long bones (the radius and the ulna), the interosseous membrane, and multiple arteries, nerves, and muscles. Forearm: Anatomy muscles and their associated movements. The name of each muscle is a reflection of the action of the muscle on the wrist and hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy.

Notable Anatomical Features

Carpal tunnel Carpal Tunnel The carpal tunnel is formed by the transverse carpal ligament (flexor retinaculum) superiorly and the carpal bones inferiorly. Carpal Tunnel Syndrome

The carpal tunnel Carpal Tunnel The carpal tunnel is formed by the transverse carpal ligament (flexor retinaculum) superiorly and the carpal bones inferiorly. Carpal Tunnel Syndrome is formed by the following:

• Anteriorly: the fibrous Fibrous Fibrocystic Change flexor retinaculum Flexor Retinaculum Ankle Joint: Anatomy 
• Posteriorly: the concave palmar surface of the carpal bones Carpal bones The eight bones of the wrist: scaphoid bone; lunate bone; triquetrum bone; pisiform bone; trapezium bone; trapezoid bone; capitate bone; and hamate bone. Carpal Tunnel Syndrome 
• Contents of the carpal tunnel Carpal Tunnel The carpal tunnel is formed by the transverse carpal ligament (flexor retinaculum) superiorly and the carpal bones inferiorly. Carpal Tunnel Syndrome:
  • Median nerve Median Nerve A major nerve of the upper extremity. In humans, the fibers of the median nerve originate in the lower cervical and upper thoracic spinal cord (usually C6 to T1), travel via the brachial plexus, and supply sensory and motor innervation to parts of the forearm and hand. Cubital Fossa: Anatomy
  • Tendons of the flexor digitorum superficialis Flexor digitorum superficialis Forearm: Anatomy (4)
  • Tendons of the flexor digitorum profundus Flexor digitorum profundus Forearm: Anatomy (4)
  • Tendon of the flexor pollicis longus Flexor pollicis longus Forearm: Anatomy (in radial sheath; 1)

Ulnar canal (Guyon’s canal)

• The ulnar canal or Guyon’s canal is formed by the following:
  • Superficially: palmar carpal ligament 
  • Floor: flexor retinaculum Flexor Retinaculum Ankle Joint: Anatomy and hypothenar muscles Hypothenar muscles Hand: Anatomy
  • Medially: pisiform 
  • Laterally: hook of the hamate
• Contents of the ulnar tunnel:
  • Ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy
  • Ulnar artery Ulnar Artery The larger of the two terminal branches of the brachial artery, beginning about one centimeter distal to the bend of the elbow. Like the radial artery, its branches may be divided into three groups corresponding to their locations in the forearm, wrist, and hand. Forearm: Anatomy

The anatomical snuff box

• Boundaries of the anatomical snuff box (or radial fossa Radial fossa Arm: Anatomy):
  • Lateral/radial: tendons of extensor pollicis brevis Extensor pollicis brevis Forearm: Anatomy and abductor pollicis longus Abductor pollicis longus Forearm: Anatomy 
  • Medial/ulnar: tendon of extensor pollicis longus Extensor pollicis longus Forearm: Anatomy tendon
  • Proximal: styloid process of the radius Radius The outer shorter of the two bones of the forearm, lying parallel to the ulna and partially revolving around it. Forearm: Anatomy
  • Distal: apex of the triangle created by these tendons
  • Floor: trapezium and scaphoid (palpable)
• Contents of the anatomical snuff box:
  • Radial artery Radial Artery The direct continuation of the brachial trunk, originating at the bifurcation of the brachial artery opposite the neck of the radius. Its branches may be divided into three groups corresponding to the three regions in which the vessel is situated, the forearm, wrist, and hand. Forearm: Anatomy
  • Superficial branch of radial nerve Radial Nerve A major nerve of the upper extremity. In humans the fibers of the radial nerve originate in the lower cervical and upper thoracic spinal cord (usually C5 to T1), travel via the posterior cord of the brachial plexus, and supply motor innervation to extensor muscles of the arm and cutaneous sensory fibers to extensor regions of the arm and hand. Axilla and Brachial Plexus: Anatomy ( meralgia paresthetica Meralgia Paresthetica Mononeuropathy and Plexopathy: compression Compression Blunt Chest Trauma or injury of this nerve at the wrist)
  • Origin of the cephalic vein
  • Scaphoid and trapezium bones

Clinical Relevance

Common problems associated with the wrist

• Carpal tunnel Carpal Tunnel The carpal tunnel is formed by the transverse carpal ligament (flexor retinaculum) superiorly and the carpal bones inferiorly. Carpal Tunnel Syndrome syndrome: the most common compressive neuropathy Neuropathy Leprosy, which may be precipitated by repetitive vibration Vibration A continuing periodic change in displacement with respect to a fixed reference. Neurological Examination and motions. Associated with diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus, thyroid Thyroid The thyroid gland is one of the largest endocrine glands in the human body. The thyroid gland is a highly vascular, brownish-red gland located in the visceral compartment of the anterior region of the neck. Thyroid Gland: Anatomy disease, rheumatoid arthritis Arthritis Acute or chronic inflammation of joints. Osteoarthritis, and pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care. Occurs from the narrowing of the carpal tunnel Carpal Tunnel The carpal tunnel is formed by the transverse carpal ligament (flexor retinaculum) superiorly and the carpal bones inferiorly. Carpal Tunnel Syndrome and subsequent compression Compression Blunt Chest Trauma of the median nerve Median Nerve A major nerve of the upper extremity. In humans, the fibers of the median nerve originate in the lower cervical and upper thoracic spinal cord (usually C6 to T1), travel via the brachial plexus, and supply sensory and motor innervation to parts of the forearm and hand. Cubital Fossa: Anatomy and the 9 flexor tendons within it. Can lead to pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and paresthesia in the median nerve Median Nerve A major nerve of the upper extremity. In humans, the fibers of the median nerve originate in the lower cervical and upper thoracic spinal cord (usually C6 to T1), travel via the brachial plexus, and supply sensory and motor innervation to parts of the forearm and hand. Cubital Fossa: Anatomy distribution and thenar muscle atrophy Thenar Muscle Atrophy Carpal Tunnel Syndrome.
• Scaphoid fracture Scaphoid Fracture Hand and Wrist Pain: the most commonly fractured carpal bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types; occurs secondary to a fall onto an outstretched hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy and presents with tenderness at the anatomical snuffbox. Treatment can include prolonged wrist immobilization Immobilization Delirium or surgical intervention and complications including nonunion Nonunion Hip Fractures and avascular necrosis Avascular Necrosis Hip Fractures.
• Lunate dislocation Lunate Dislocation Hand and Wrist Pain: anterior dislocation may precipitate acute carpal tunnel Carpal Tunnel The carpal tunnel is formed by the transverse carpal ligament (flexor retinaculum) superiorly and the carpal bones inferiorly. Carpal Tunnel Syndrome syndrome. These injuries are commonly missed on initial presentation.
• De Quervain’s tenosynovitis: a stenosing tenosynovitis of the 1st dorsal compartment, which consists of the abductor pollicis longus Abductor pollicis longus Forearm: Anatomy and extensor pollicis brevis Extensor pollicis brevis Forearm: Anatomy. Usually occurs secondary to repetitive motion/overuse and may be associated with rheumatoid arthritis Arthritis Acute or chronic inflammation of joints. Osteoarthritis and mothers with toddlers. Classic physical examination test is Finkelstein’s maneuver.  
• Ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy neuropathy Neuropathy Leprosy or entrapment: The ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy may be compressed or traumatically injured at the wrist within the ulnar or Guyon’s canal. The injury causes paresthesias Paresthesias Subjective cutaneous sensations (e.g., cold, warmth, tingling, pressure, etc.) that are experienced spontaneously in the absence of stimulation. Posterior Cord Syndrome, numbness, and/or pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways in the ulnar half of the hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy, and in severe cases may lead to “claw hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy” (4th and 5th finger hyperextension at metacarpophalangeal joints Metacarpophalangeal joints The articulation between a metacarpal bone and a phalanx. Examination of the Upper Limbs and flexion Flexion Examination of the Upper Limbs of the interphalangeal joints Interphalangeal joints Hand: Anatomy).  Also called “handlebar palsy Palsy paralysis of an area of the body, thus incapable of voluntary movement Cranial Nerve Palsies” in cyclists.

Important physical examination tests of the wrist

• Watson’s test: used to assess for ligamentous instability between the scaphoid and lunate bones. The examiner grasps the wrist in slight extension Extension Examination of the Upper Limbs and ulnar deviation with thumb over the scaphoid tubercle on the palmar side of the wrist. Pressure is then applied to the scaphoid while the patient’s hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy is deviated radially. A positive test is localized pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways or laxity.
• Finkelstein’s test Finkelstein’S Test Hand and Wrist Pain: used in the assessment of de Quervain’s tenosynovitis. The patient makes a fist around their thumb and moves the hand Hand The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median and ulnar nerves. Hand: Anatomy into ulnar deviation. A positive test is sharp pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways over the tendons in the first dorsal compartment along the distal radial styloid.
• Tinel’s sign: Used in the evaluation of carpal tunnel Carpal Tunnel The carpal tunnel is formed by the transverse carpal ligament (flexor retinaculum) superiorly and the carpal bones inferiorly. Carpal Tunnel Syndrome syndrome, this test is done by lightly tapping over the median nerve Median Nerve A major nerve of the upper extremity. In humans, the fibers of the median nerve originate in the lower cervical and upper thoracic spinal cord (usually C6 to T1), travel via the brachial plexus, and supply sensory and motor innervation to parts of the forearm and hand. Cubital Fossa: Anatomy on the volar surface of the wrist. A positive test elicits paresthesia in the median nerve Median Nerve A major nerve of the upper extremity. In humans, the fibers of the median nerve originate in the lower cervical and upper thoracic spinal cord (usually C6 to T1), travel via the brachial plexus, and supply sensory and motor innervation to parts of the forearm and hand. Cubital Fossa: Anatomy distribution.
• Phalen’s sign: Patient flexes both wrists and pushes the dorsal surfaces of both hands together for 30–60 seconds. A positive test elicits burning or tingling Tingling Posterior Cord Syndrome in the distribution of the median nerve Median Nerve A major nerve of the upper extremity. In humans, the fibers of the median nerve originate in the lower cervical and upper thoracic spinal cord (usually C6 to T1), travel via the brachial plexus, and supply sensory and motor innervation to parts of the forearm and hand. Cubital Fossa: Anatomy, suggestive of carpal tunnel Carpal Tunnel The carpal tunnel is formed by the transverse carpal ligament (flexor retinaculum) superiorly and the carpal bones inferiorly. Carpal Tunnel Syndrome syndrome.