What term refers to a condition involving immovable joints?

The term that refers to a condition involving immovable joints is synarthrotic. Synarthrotic joints are characterized by their inability to move, as they are connected by fibrous tissues or cartilage. This type of joint is essential in providing stability and support to certain areas of the body, such as the skull, where the joints between the bones allow for no movement to protect the brain and maintain structural integrity.

In comparison, amphiarthrotic joints allow for slight movement and are connected by cartilage; examples include the joints in the spine. Diarthrotic joints, also known as synovial joints, are highly mobile and include the majority of the body's joints, such as the knees and elbows. Tendinitis, on the other hand, refers to the inflammation of the tendons and is not related to joint classification. Therefore, synarthrotic is the appropriate term for indicating a condition of immovable joints.