What is meant by double joint?

　　A biaxial joint generally refers to a joint with two perpendicular axes of motion, allowing movement in two different directions. A detailed explanation is as follows:

　　Compared to uniaxial joints, biaxial joints have a greater range of motion because they can move along two distinct axes. These joints typically consist of two spherical or hemispherical surfaces, with one surface fitting into the other. However, such joints tend to be less stable and are more prone to injuries such as dislocations. Examples include the wrist joint and ankle joint.

　　In daily life, if joint discomfort symptoms occur—such as restricted movement or pain—it is recommended to seek proper medical treatment under the guidance of an orthopedic physician to help alleviate symptoms.