The wrist connects the hand to the forearm. It consists of the distal ends of the radius and ulna bones, eight carpal bones, and the proximal ends of five metacarpal bones. This arrangement of bones allows for a wide range of movement. The wrist can bend, straighten, move laterally, and rotate. It is relatively prone to injury. Force or stress can injure any of the bones.

There are 10 bones in the human wrist:

• 8 carpal bones
  • Proximal Carpal Row
    • Scaphoid
    • Lunate
    • Triquetrum
    • Pisiform
  • Distal Carpal Row
    • Trapezium
    • Trapezoid
    • Capitate
    • Hamate
• 2 long bones of forearm
  • Radius
  • Ulna

These 10 bones form 8 joints within the wrist and hand:

• Distal radioulnar joint in the forearm, which is located between the two long bones of the forearm, the radius and ulna. This joint allows for rotation of the forearm. The radius moves, while the ulna remains stable.
• Radiocarpal joint where the radius meets the proximal carpal row. This is the main joint of the wrist. The radius articulates with the scaphoid and lunate in particular in the proximal carpal row.
• Midcarpal joint between the proximal and distal carpal rows. This joint provides less movement than the radiocarpal joint, however it assists the radiocarpal joint with various wrist movements.
• 5 carpometacarpal (CMC) joints between the metacarpals of the hand and the distal carpal row of bones in the wrist
• There is no direct articulation between the ulna and carpals, but rather this is called the ulnocarpal complex as the ulna and the lunate and triquetrum are connected via the Triangular Fibrocartilage Complex (TFCC), which is a complex of ligaments and cartilage to provide stability to the wrist during movement.

All of these bones and joints help us move our wrist to function in all of our everyday activities. Some common bone and joint conditions of the wrist include osteoarthritis, rheumatoid arthritis, joint dislocations, and wrist fractures of either the radius, ulna, or carpals.

Ligaments are strong fibrous bands of tissue that connect bone to bone. These provide stability and assist with mobility to joints throughout motion. There are two types of ligaments in the wrist, extrinsic and intrinsic. 

• Extrinsic ligaments- these connect the long bones of the forearm and the bones in the hand to the carpal bones. These include:
  • Volar ligaments- radioscaphocapitate ligament, volar radiotriquetral ligament, ulnolunate ligament, ulnotriquetral ligament, ulnocapitate ligament, and volar radioulnar ligament
  • Dorsal ligaments- dorsal intercarpal ligament, dorsal radiotriquetral ligament, dorsal radioulnar ligament
  • Other ligaments- radial collateral ligament, ulnar collateral ligament
• Intrinsic ligaments- these connect various carpal bones together. These include:
  • Proximal interosseous ligaments- scapholunate ligament (SL) and lunotriquetral ligament (LT)
  • Midcarpal ligaments- scaphotrapeziotrapezoid ligament (STT), scaphocapitate ligament, triquetrohamatecapitate ligament, and triquetrohamate ligament
  • Distal interosseous ligaments- capitotrapezoid ligament and capitohamate ligament
  • Other ligaments- triangular fibrocartilage complex (TFCC)
• Thumb ligaments- these attach the thumb to the carpal bones in the wrist
  • Superficial and deep anterior oblique ligaments and dorsoradial ligament

Some of the common conditions of ligaments in the wrist include a wrist sprain, which is a stretching or tearing of any of the ligaments in the wrist. If these are left untreated, they can often lead to earth degenerative conditions such as arthritis, Scapho-lunate Advanced Collapse (SLAC), and other debilitating wrist conditions. 

There are numerous tendons of various muscles that insert into the wrist to allow it to perform all of its motions and functions. Tendons attach muscles to bones.

• Flexor Carpi Radialis (FCR)- Begins at medial or middle elbow and attaches to metacarpals 2 and 3 and the trapezium. This bends, or flexes, the wrist. 
• Flexor Carpi Ulnaris (FCU)- Begins at medial or middle elbow and attaches to metacarpal 5 and the pisiform. This also bends, or flexes, the wrist.
• Palmaris Longus (PL)- This tendon is not found in everyone and therefore, it does not have a lot of function for wrist motion. It is often used to repair other structures as needed.
• Extensor Carpi Radialis Brevis (ECRB)- Begins at the lateral or outside elbow and attaches to the base of the hand on the thumb side. It is one of three tendons to extend the wrist backwards.
• Extensor Carpi Radialis Longus (ECRL)- Begins at the lateral or outside of the elbow and attaches to the hand. It is another tendon that extends the wrist backwards.
• Extensor Carpi Ulnaris (ECU)- Begins at the lateral or outside of the elbow and attaches to the base of the hand on the small finger side. It is the last of the three tendons to extend the wrist backwards. It also helps the wrist to ulnarly deviate, or move the hand towards the small finger side. 

Some of the most common conditions that affect the tendons of the wrist include Dequervain’s tenosynovitis, ECU, FCR, or FCU tendonitis, snapping ECU syndrome.

Peripheral nerves are tubes that extend out of the spinal cord and transmit electrical impulses that provide sensory and motor information to various stimuli and muscles to allow us to feel and move our body. There are a variety of nerves in the upper extremities, mostly of which originate from our neck, or cervical spine. 

• Brachial Plexus- a group of nerves that control the muscles and the sensation throughout the arms. 
  • There are various components of the brachial plexus including, roots, trunks, divisions, cords, and branches. An injury can occur at any of these components, causing various symptoms depending on the location.
  • Injuries can range from mild stretch to complete tears at the roots, which results in an arm with no sensation or ability to move or function. 
  • Injuries often occur during accidents where the neck and arm move in opposite directions, as can occur in motor vehicle accidents or birth trauma.
• Radial Nerve- begins at the nerve roots C5, C6, C7, C8, and T1 in the brachial plexus. It wraps around the humerus and provides input to the triceps muscle, which extends the elbow. It travels around the outside of the elbow into the dorsal forearm and provides the input to the muscles that extend the wrist and fingers. 
  • This nerve provides the sensation to the back of the wrist on the thumb side, hand and thumb, except the small and ring fingers. 
  • Injuries can occur with injury to the humerus and from compression in the forearm, called “radial tunnel syndrome.” Injuries can cause weakness in the ability to extend the wrist and fingers to paralysis and the inability to extend the wrist and fingers, called wrist drop.
• Median Nerve- begins at the nerve roots C5, C6, C7, C8, and T1 in the brachial plexus. While this nerve travels along the inside of the upper arm, it does not provide any function or sensation until it crosses the elbow. In the forearm, it provides input to the muscles the flex the fingers and wrist and the muscles the pronate (palm down) the forearm. It also supplies the muscles in the thenar eminence (OP, FPB, and APB) and lumbricals 1 and 2.  It does not supply the FCU or the FDP muscles of the small and ring fingers, which is supplied by the ulnar nerve. 
  • This nerve provides the sensation to the palm side of the wrist on the thumb side, palm over the thenar muscles, the thumb, index, long, and half of the ring finger.
  • Injuries can cause weakness in forearm pronation, wrist flexion, and finger flexion. There may also be thenar muscle atrophy and difficulty with opposition of the thumb. Finally, there may be altered sensation such as numbness, tingling, or pins and needles to palm over the thenars, thumb, index, long, and half of the ring finger.
• Ulnar Nerve- begins at C8 and T1 nerve roots in the brachial plexus. It travels down the inside of the upper arm to the inside of the elbow. The “funny bone” feeling that travels down to the small and ring finger when you hit the inside of the elbow is actually the ulnar nerve. The inside of the elbow is a common point of compression, called cubital tunnel syndrome. It then continues to travel down the inside of the forearm into the side of the hand by the small finger. The ulnar nerve is responsible for providing input to the FDP muscles of the small and ring fingers (bends DIP joint of small and ring fingers), the FCU (flexes wrist and ulnarly deviates), hypothenar muscles, lumbricals 3 and 4, and the palmar and dorsal interossei. 
  • This nerve provides sensation to the back and palm side of the wrist on the small finger side, small finger side of the palm, the small finger and half of the ring finger, and the back (dorsal) side of the small finger.
  • Injuries can provide a variety of symptoms including altered sensations such as tingling, numbness, pins and needles to the small finger side of the palm, small finger, and half of the ring finger, weakness in many of the intrinsic muscles of the hand, causing decreased grip strength, and “clawing” of the small and ring fingers due to muscle imbalances.

Some of the most common conditions that affect the nerves of the wrist include brachial plexus injuries, carpal tunnel syndrome, cubital tunnel syndrome, anterior interosseous nerve syndrome, or posterior interosseous nerve syndrome.