A joint disc, also known as an articular disc, is a plate of fibrocartilage found within some synovial joints, separating the joint cavity. This separation allows for more complex and varied movements within the joint.
Function of Joint Discs
Joint discs serve several important functions:
- Improved Joint Congruity: They help to improve the fit between the articulating bones, especially when the bone surfaces are incongruent. This better fit enhances joint stability and reduces stress concentration.
- Shock Absorption: They can act as shock absorbers, distributing loads and reducing stress on the articular cartilage and underlying bone.
- Increased Joint Stability: The disc deepens the articular surfaces, thus increasing the stability of the joint and decreasing the risk of dislocation.
- Lubrication: They contribute to joint lubrication by helping to distribute synovial fluid throughout the joint.
- Separate Movements: As the reference mentions, the disc divides the synovial cavity into two separate spaces, allowing for different movements to occur in each space.
Examples of Joints with Articular Discs
Here are a few examples of joints that feature articular discs:
- Temporomandibular Joint (TMJ): Located in the jaw, the TMJ disc is crucial for chewing and speaking.
- Sternoclavicular Joint: Connects the clavicle (collarbone) to the sternum (breastbone).
- Ulnocarpal Joint: Located in the wrist, between the ulna and the carpal bones.
Structure
A joint disc is made of fibrocartilage, which is a type of cartilage containing a high proportion of collagen fibers. This composition gives the disc its strength and resilience, allowing it to withstand compressive forces and resist tearing.
In summary, a joint disc is a specialized cartilage structure found in certain synovial joints that enhances joint function by improving fit, absorbing shock, increasing stability, aiding in lubrication, and enabling diverse movements.
