Caroline Girard RMT

🔈 POSSIBLE CAUSES OF KNEE PAIN

🔈THE SIX TYPES OF SYNOVIAL JOINTS

Synovial joints are classified according to the shape of their articulating surfaces and/or the type of movement they permit.

1. Plane joints permit gliding or sliding movements in the plane of the articular surfaces. The opposed surfaces of the bones are flat or almost flat, with movement limited by their tight joint capsules. Plane joints are numerous and are nearly always small. An example is the acromioclavicular joint between the acromion of the scapula and the clavicle.

2. Hinge joints permit flexion and extension only, movements that occur in one plane (sagittal) around a single axis that runs transversely; thus, hinge joints are uniaxial joints. The joint capsule of these joints is thin and lax anteriorly and posteriorly where movement occurs; however, the bones are joined by strong, laterally placed collateral ligaments. The elbow joint is a hinge joint.

3. Saddle joints permit abduction and adduction as well as flexion and extension, movements occurring around two axes at right angles to each other; thus, saddle joints are biaxial joints that allow movement in two planes, sagittal and frontal. The performance of these movements in a circular sequence (circumduction) is also possible. The opposing articular surfaces are shaped like a saddle (i.e., they are reciprocally concave and convex). The carpometacarpal joint at the base of the 1st digit (thumb) is a saddle joint.
4. Condyloid joints permit flexion and extension as well as abduction and adduction; thus, condyloid joints are also biaxial. However, movement in one plane (sagittal) is usually greater (freer) than in the other. Circumduction, more restricted than that of saddle joints, is also possible. The metacarpophalangeal joints (knuckle joints) are condyloid joints.

5. Ball and socket joints allow movement in multiple axes and planes: flexion and extension, abduction and adduction, medial and lateral rotation, and circumduction; thus, ball and socket joints are multiaxial joints. In these highly mobile joints, the spheroidal surface of one bone moves within the socket of another. The hip joint is a ball and socket joint in which the spherical head of the femur rotates within the socket formed by the acetabulum of the hip bone.

6. Pivot joints permit rotation around a central axis; thus, they are uniaxial. In these joints, a rounded process of bone rotates within a sleeve or ring. The median atlanto-axial joint is a pivot joint in which the atlas (C1 vertebra) rotates around a finger-like process, the dens of the axis (C2 vertebra), during rotation of the head.