The primary difference between intrinsic and extrinsic ligaments lies in their location and biomechanical properties within the wrist. Intrinsic ligaments reside entirely within the carpus, connecting carpal bones, while extrinsic ligaments connect the carpal bones to the radius or ulna. Furthermore, intrinsic ligaments generally exhibit greater elongation capabilities before permanent deformation compared to the stiffer extrinsic ligaments.
Intrinsic Ligaments
- Location: Situated entirely within the carpus, connecting carpal bones to each other.
- Biomechanical Properties: More elastic and capable of greater elongation before permanent damage occurs. Think of them as shock absorbers within the wrist.
- Function: Primarily responsible for maintaining carpal bone stability and kinematic motion within the carpus.
- Examples: Scapholunate interosseous ligament (SLIL), Lunotriquetral interosseous ligament (LTIL).
Extrinsic Ligaments
- Location: Connect the carpal bones to the radius or ulna (bones of the forearm). They extend outside the carpus.
- Biomechanical Properties: Stiffer and less elastic than intrinsic ligaments. They provide more rigid support.
- Function: Primarily responsible for connecting the wrist to the forearm and transferring load between the forearm and hand. They also influence overall wrist stability.
- Examples: Radioscaphocapitate ligament, Dorsal radiocarpal ligament, Ulnolunate ligament.
Table Summarizing Key Differences
| Feature | Intrinsic Ligaments | Extrinsic Ligaments |
|---|---|---|
| Location | Within the carpus (between carpal bones) | Connect carpus to radius/ulna (forearm) |
| Stiffness | More elastic | Stiffer |
| Elongation | Greater elongation before deformation | Less elongation before deformation |
| Primary Role | Carpal bone stability within the carpus | Connect wrist to forearm; overall stability |
In essence, intrinsic ligaments fine-tune carpal bone movements, while extrinsic ligaments provide the foundation that links the wrist to the rest of the arm. Both types are critical for proper wrist function.
