Carpal and Tarsal Joints: Anatomy, Function, and Clinical Significance

What joints are between carpal and tarsal bones?

The primary joints involving the carpal bones include the radiocarpal joint connecting to the forearm, and numerous intercarpal joints within the wrist itself. Similarly, the tarsal bones articulate at the talocrural (ankle) joint with the leg bones, and several crucial intertarsal joints, such as the subtalar and transverse tarsal joints, within the foot.

Understanding the Carpal Bones and Their Joints (Wrist)

The carpal bones are eight small, irregularly shaped bones arranged in two rows within the wrist. These bones, while small, are critical for the wrist's remarkable dexterity, strength, and stability. The joints associated with them allow for complex movements of the hand relative to the forearm.

• Radiocarpal Joint: This is the primary joint connecting the forearm to the hand. It is formed by the distal end of the radius and the articular disc of the ulna proximally, articulating with the scaphoid, lunate, and triquetrum (three of the proximal carpal bones) distally. This ellipsoid-type synovial joint permits flexion, extension, abduction (radial deviation), adduction (ulnar deviation), and circumduction of the wrist.
• Intercarpal Joints: These are the multiple small joints located between individual carpal bones within both the proximal and distal rows, and also between the two rows themselves. They are typically plane (gliding) synovial joints, allowing for limited gliding movements that collectively contribute to the overall range of motion and adaptability of the wrist.
  • Midcarpal Joint: This is a functionally significant joint located between the proximal row (scaphoid, lunate, triquetrum) and the distal row (trapezium, trapezoid, capitate, hamate) of carpal bones. It contributes substantially to wrist flexion and extension, working synergistically with the radiocarpal joint.
  • Individual Intercarpal Articulations: Each carpal bone articulates with its neighbors (e.g., scaphoid with lunate, capitate with hamate), allowing subtle movements that optimize grip and force transmission.

Understanding the Tarsal Bones and Their Joints (Ankle and Foot)

The tarsal bones consist of seven bones forming the posterior part of the foot (the ankle and heel). These bones are larger and more robust than the carpals, designed to bear the body's weight and provide leverage for locomotion. The joints associated with them are fundamental to ankle and foot stability, shock absorption, and propulsion.

• Talocrural Joint (Ankle Joint): This is the primary hinge joint connecting the leg to the foot. It is formed by the distal ends of the tibia and fibula (forming the malleoli) articulating with the trochlea of the talus. This joint primarily allows for dorsiflexion (lifting the foot upwards) and plantarflexion (pointing the foot downwards).
• Subtalar Joint: Located directly below the talocrural joint, this crucial joint is formed by the articulation between the talus superiorly and the calcaneus (heel bone) inferiorly. It is primarily responsible for the complex movements of inversion (sole of the foot turns inward) and eversion (sole of the foot turns outward), which are vital for adapting the foot to uneven surfaces and absorbing ground reaction forces.
• Transverse Tarsal Joint (Chopart's Joint): This is a functional joint line that comprises two separate but synergistic articulations:
  • Talonavicular Joint: Articulation between the talus and the navicular bone.
  • Calcaneocuboid Joint: Articulation between the calcaneus and the cuboid bone. These two joints work together to contribute significantly to foot inversion and eversion, especially during dynamic activities like walking and running.
• Intertarsal Joints: This is a collective term for the numerous small joints between the other tarsal bones (e.g., cuneonavicular, intercuneiform, cuboidonavicular). Like their carpal counterparts, these are typically plane synovial joints that allow for limited gliding movements. Individually, their movements are small, but collectively, they contribute to the overall flexibility and adaptability of the foot's arch system, distributing forces and absorbing shock.
• Tarsometatarsal Joints (Lisfranc's Joint): While technically distal to the main tarsal complex, these joints connect the tarsal bones (specifically the cuboid and cuneiforms) to the bases of the five metatarsal bones. They are crucial for maintaining the longitudinal and transverse arches of the foot and play a role in propulsion during gait.

Functional Significance

The intricate network of joints within the carpal and tarsal regions highlights the sophisticated design of the human appendicular skeleton.

• Wrist (Carpals): The collective motion allowed by the radiocarpal and intercarpal joints provides the hand with exceptional mobility and fine motor control. This allows for precise manipulation of objects, powerful gripping, and effective force transmission from the forearm to the hand. The stability provided by the numerous ligaments binding these small bones is critical for preventing collapse under load.
• Ankle and Foot (Tarsals): The talocrural, subtalar, and intertarsal joints are fundamental to bipedal locomotion. They allow the foot to act as both a rigid lever for propulsion (e.g., during push-off) and a flexible adapter for shock absorption and navigating varied terrains (e.g., during initial contact). The precise interplay between these joints ensures optimal alignment, balance, and efficient transfer of forces through the lower limb during weight-bearing activities.

Clinical Relevance

Understanding these joints is crucial for diagnosing and treating common musculoskeletal conditions. Injuries such as wrist sprains (often involving intercarpal ligaments), ankle sprains (commonly affecting the talocrural and subtalar joints), and midfoot sprains (Lisfranc injuries affecting tarsometatarsal and intertarsal ligaments) are prevalent. Degenerative conditions like osteoarthritis can also affect these weight-bearing and high-mobility joints, leading to pain and functional limitations.

Conclusion

The joints between the carpal bones (intercarpal, including the midcarpal) and the major joint connecting the forearm to the carpals (radiocarpal) provide the wrist with its remarkable range of motion and stability. Similarly, the joints between the tarsal bones (intertarsal, including the subtalar and transverse tarsal joints) and the primary ankle joint connecting the leg to the tarsals (talocrural) are essential for the foot's ability to adapt to surfaces, absorb shock, and propel the body. These complex articulations are fundamental to human movement, efficiency, and overall functional capacity of the upper and lower limbs.