A saddle joint is a type of synovial joint where one bone has a concave surface and the other has a convex surface, resembling a saddle. This unique structure allows for biaxial movement, meaning movement in two planes: the sagittal (forward and backward) and frontal (side to side).
Examples of Saddle Joints
Here are examples of saddle joints found in the human body, as noted in the provided reference:
- Carpometacarpal joint of the thumb: This is perhaps the most well-known example. It allows the thumb to move across the palm, a crucial motion for grasping.
- Sternoclavicular joint of the thorax: This joint connects the sternum (breastbone) to the clavicle (collarbone), contributing to shoulder movement.
- Incusmalleolar joint of the middle ear: This is one of the small joints within the ear that helps transmit sound vibrations.
- Calcaneocuboid joint of the heel: Located in the foot, this joint contributes to foot flexibility and movement.
Key Characteristics of Saddle Joints
Saddle joints are biaxial. According to the reference, the movements that the saddle joints allow are in the sagittal and frontal planes. This means they permit:
- Flexion and Extension: Movement in the sagittal plane.
- Abduction and Adduction: Movement in the frontal plane.
- Circumduction: A circular motion that combines flexion, extension, abduction, and adduction.
Table of Saddle Joints
| Joint | Location | Movements Allowed |
|---|---|---|
| Carpometacarpal (Thumb) | Hand | Flexion/Extension, Abduction/Adduction, Circumduction |
| Sternoclavicular | Thorax (Shoulder) | Elevation/Depression, Protraction/Retraction, Rotation |
| Incusmalleolar | Middle Ear | Minimal, primarily vibration transmission |
| Calcaneocuboid | Heel (Foot) | Limited Inversion/Eversion, Flexion/Extension |
Understanding the specific structure and function of saddle joints is crucial in fields such as anatomy, physical therapy, and sports medicine.
