Hand anatomy explained

The human hand comprises 27 bones, including the carpal bones, the metacarpals, and the phalanges. At the distal end of the upper extremity kinetic chain, the hand gives us the ability to perform fine motor skills.

The wrist is the articulation of the forearm (radius and ulna) with the hand (carpal bones). There are eight carpal bones, including a proximal row (articulates with the distal radius and ulna) and a distal row (articulates with the metacarpals).

The hand has some of the densest areas of nerve endings in the body, which allows for a tremendous sense of touch and the most significant positioning capability.

There are extrinsic muscles that move the hand and wrist. Finger flexors and extensors originate in the forearm. Their tendons cross the wrist and insert at various points on the phalanges to allow finger flexion (bending, grasping) or finger extension (straightening). There are also intrinsic muscles in the hand that control finger or thumb movements.

5 common hand and/or wrist injuries

Because of the hand’s complexity and its unique necessity in daily living activities, injuries to the hand and wrist can be debilitating for the individual. Injuries can affect the bones, tendons, nerves, and ligaments.

Additionally, the integrity of the skin and underlying tissue can be affected by burns. Skilled medical care following a hand injury, including physical and occupational therapy, is critical in regaining functional capabilities.

Fractures

Fractures of the hand can occur in either the fingers’ small bones (phalanges) or the long bones (metacarpals). They can result from a twisting injury, a fall, a crush injury, or direct contact in sports.

Fractures in the wrist can include the carpal bones or the distal forearm. These injuries can result from a fall or a direct blow. Here are examples of common fractures involving the hand and wrist.

  • Distal Radius Fracture (Colles Fracture)
  • Hand/Finger Fractures (Boxer’s Fracture)
  • Carpal Fracture (Scaphoid Fracture)

A physician should evaluate suspected fractures in the fingers or wrist. Depending on radiographic and exam findings, a period of immobilization will occur. Some fractures require surgery with screws/plates or pins and wires.

The goal of immobilization is to allow the bone to heal. Displaced fractures will generally heal in 4-6 weeks. Following immobilization and surgery, stiffness, hypersensitivity, and weakness may occur.

Physical and occupational therapy will focus on regaining motion, strength and improving the ability to perform functional activities and fine motor skills.

Tendon injuries

The tendons of the hand and thumb can be injured through a variety of mechanisms. Laceration from a sharp object can result in the severing of one or multiple tendons.

Overuse and repetitive motion can cause tendons and tendon sheaths to become inflamed and thickened, resulting in pain, weakness, and loss of function. Other medical conditions like rheumatoid arthritis can cause tendon disruption due to the soft tissue’s weakening.

Below are several examples of tendon injuries that can occur.

Tendon Rupture

  • Tendon Laceration: A medical emergency. Lacerations typically occur from a traumatic insult from a sharp object. Tendons must be repaired microscopically by a hand surgeon, usually an orthopedic or plastic surgeon. Rehabilitation requires extensive splinting to protect the damaged tendons while maintaining mobility of other structures. As the tendons heal, the focus will shift towards regaining strength and function in the affected hand. Tendon lacerations can occur in multiple zones, including the wrist, hand, and fingers.
  • Mallet Finger: This condition is usually the result of a direct blow to the fingertip. It results in damage to the extensor tendon insertion at the distal phalanx. The resulting deformity is a fingertip that cannot be fully straightened actively. Treatment involves splinting using a splint that keeps the finger’s tip extended while allowing other movements at other joints in the finger. This allows the damaged tendon to heal, which can take 6-8 weeks. Stiffness is often present, and a physical therapist will work to restore motion and the ability to perform activities of daily living.
  • Boutonniere Deformity: Boutonnière deformity results from an injury to the tendons that straightens the middle joint of your finger (extensor). This results in a middle finger joint that will not straighten. This injury can be caused by a direct blow, a laceration, or arthritis. Treatment will include specific splinting, stretching exercises, and patient education in protection.

Tendonitis (tendinosis): Tendons that cross the wrist into the hand or thumb can become inflamed through overuse or repetitive motion. This causes pain and discomfort with specific movements, depending on the area of injury. Tendinosis refers to tendons’ non-inflammatory condition where thickening of the tendon occurs along with the tendon tissue’s breakdown over time.

  • DeQuervain’s Tendinosis: De Quervain’s tendinosis occurs when the tendons around the thumb base are irritated or constricted. The word “tendinosis” refers to a swelling of the tendons. As the tendons swell, they become irritated by repetitive motion, resulting in pain and tenderness. The goal of treatment is to reduce the pain through splinting and protection, instrument-assisted soft tissue mobilization, and activity modification. NSAIDs or corticosteroid injections may also be prescribed by a physician in some instances.

Nerve Injuries

Three nerves cross the wrist that supplies the hand’s motor and sensory ability. The hand has the densest concentration of nerve endings in the body. Therefore it’s not uncommon for the nerves to be affected in an injury.

With significant lacerations and associated surgery and trauma, nerves can be affected, resulting in loss of sensation. In other cases, nerves that cross the wrist can become compressed or compromised over time. This can be because of multiple factors, including age, sex, heredity, activity, pregnancy, and medical conditions like diabetes.

Here are two examples of the most common non-traumatic nerve conditions affecting the hand/wrist.

  • Carpal Tunnel Syndrome: Carpal tunnel syndrome is a common source of hand numbness and pain, occurring more often in women than men. The carpal tunnel refers to the “tunnel” created by the carpal arch and the transverse carpal ligament. The finger flexors and median nerve pass through this tunnel. “Carpal tunnel syndrome” occurs when the tissues surrounding the flexor tendons in the wrist swell and put pressure on the median nerve, resulting in numbness and weakness in the hand. Rarely is there one identified the cause of carpal tunnel syndrome. Typically, the cause of the condition is multi-factorial, and it develops over time. Additionally, because the median nerve in the wrist/hand is a continuation of the neural plexus leaving the cervical spine crossing the shoulder and elbow, there are often other areas where the nerve can be compromised. This “double crush” theory makes the diagnosis and treatment more complex. As such, evaluation and treatment by a physical or occupational therapist should focus on the entire upper extremity kinetic chain, not just the wrist. Conservative treatment includes splinting, patient education, activity modification, and joint protection. Neural gliding can assist.
    • Carpal Tunnel Release: Performed either arthroscopically or “open.” The transverse carpal ligament is released, reducing the pressure on the median nerve in the carpal tunnel. Physical or occupational therapy following a carpal tunnel release will follow the specific physician’s protocol. Generally speaking, emphasis will be on nerve gliding, splinting, and gentle ROM of the fingers progressing to functional activities when appropriate.
  • Ulnar Tunnel Syndrome: Ulnar tunnel syndrome occurs when the ulnar nerve is compressed at the wrist. The ulnar nerve is one of the three primary nerves that provide feeling and function to the hand. It travels from your neck down into your hand and can be constricted in several places along the way. Symptoms usually develop gradually and include weakness and numbness on the little finger side of the hand. Causes can occur because of a cyst or positioning during work or sport. Conservative treatment is geared towards changing or eliminating aggravating factors through splinting, patient education, and positioning.

Ligament Injuries

There is a multitude of ligaments that support the joints in the hand and thumb. A sprain is a ligament injury when the ligament is stretched beyond its normal range of motion.

There are ligaments in the thumb called the collateral ligaments that are most commonly sprained, typically in sports. The thumb is essential for grasping activities. Therefore, injuries can significantly limit function.

  • Skier’s Thumb: This is an injury to the ulnar collateral ligament of the thumb. This injury usually occurs from a fall on an outstretched hand. In a skier case, this injury occurs when they land with their hand on their ski pole, resulting in ligament damage. Conservative treatment includes splinting so that the ligament has time to heal, followed by strengthening exercises and return to functional activities.

Arthritis

The hand and wrist have multiple small joints that work together to provide motion, including the subtle motion needed to button a shirt or thread a needle. When the joints in the hand are affected by arthritic changes, daily living activities become more difficult and painful. There are multiple causes of arthritis in the hand, but the most common are osteoarthritis and rheumatoid arthritis.

Osteoarthritis vs. Rheumatoid Arthritis

  • Osteoarthritis is much more common and generally affects people as they age. Also known as “wear and tear” arthritis, osteoarthritis causes articular cartilage to wear away. It appears in a predictable pattern in certain joints of the hand. Often the thumb (CMC) joint is most affected.
  • Rheumatoid arthritis is a chronic disease that can affect many parts of your body. It causes the joint lining (synovium) to swell, which causes pain and stiffness in the joint. Rheumatoid arthritis most often starts in the small joints of the hands and feet. It usually affects the same joints on both sides of the body. In severe cases, rheumatoid arthritis can result in extreme degenerative changes in the hand joints leading to deformity. This affects the ability to lift, grasp, hold and manipulate objects.

Physical or occupational therapy is often prescribed as conservative care for arthritic conditions. While the disease process cannot be affected or reversed, a physical or occupational therapist will work with patients to splint painful joints, strengthen supporting muscles, and improve flexibility.

Most importantly, patients will be educated in joint preservation and protection. This includes education on compensatory mechanisms to avoid positions or activities resulting in increased pain and decreased function.

Suffering from chronic pain?
An Alves & Martinez physical therapist will complete a comprehensive evaluation to determine the musculoskeletal causes of your hand or wrist injury. Schedule an in-clinic consultation today.