Proximal interphalangeal joint

The proximal interphalangeal joint (PIP joint) is a synovial joint located in the fingers and toes. It is one of the key joints that contribute to the flexibility and dexterity of the hand and foot.

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Phalangeal joints

Anatomy

The proximal interphalangeal joint is found between the proximal phalanx and the middle phalanx of the fingers and toes. It is a hinge joint, allowing primarily for flexion and extension.

Bones

The PIP joint is formed by the articulation of two bones:

• The proximal phalanx, which is the bone closest to the metacarpophalangeal joint (MCP joint) in the fingers or the metatarsophalangeal joint (MTP joint) in the toes.
• The middle phalanx, which is the bone distal to the proximal phalanx.

Ligaments

The stability of the PIP joint is maintained by several ligaments:

• The collateral ligaments, which are located on either side of the joint and prevent excessive lateral movement.
• The volar plate, a thick fibrocartilaginous structure on the palmar side of the joint that prevents hyperextension.

Muscles

The movement of the PIP joint is controlled by the flexor and extensor muscles:

• The flexor digitorum superficialis is the primary muscle responsible for flexing the PIP joint.
• The extensor digitorum and extensor indicis muscles contribute to the extension of the joint.

Function

The primary function of the proximal interphalangeal joint is to facilitate the flexion and extension of the fingers and toes. This movement is crucial for grasping, holding, and manipulating objects, as well as for balance and locomotion in the toes.

Clinical Significance

The PIP joint is commonly affected by various conditions and injuries:

Arthritis

Osteoarthritis and rheumatoid arthritis can affect the PIP joint, leading to pain, swelling, and reduced range of motion.

Injuries

• Sprains: Damage to the ligaments surrounding the PIP joint can occur due to trauma or overuse.
• Dislocations: The PIP joint can become dislocated, often requiring medical intervention to realign the joint.
• Fractures: Fractures of the proximal or middle phalanx can involve the PIP joint, necessitating immobilization or surgical repair.

Deformities

• Boutonniere deformity: A condition where the PIP joint is flexed and the distal interphalangeal joint (DIP joint) is hyperextended.
• Swan neck deformity: Characterized by hyperextension of the PIP joint and flexion of the DIP joint.

Diagnosis

Diagnosis of PIP joint conditions typically involves:

• Physical examination to assess pain, swelling, and range of motion.
• Imaging studies such as X-rays or MRI to evaluate bone and soft tissue structures.

Treatment

Treatment options for PIP joint conditions vary depending on the underlying cause:

• Conservative management: Includes rest, ice, compression, and elevation (RICE), as well as physical therapy and splinting.
• Medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) may be used to reduce pain and inflammation.
• Surgical intervention: In cases of severe injury or deformity, surgical repair or reconstruction may be necessary.

See also

• Distal interphalangeal joint
• Metacarpophalangeal joint
• Hand anatomy

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