USMLE Step 1 Question 364

Question:

A 23 year old man is brought to the Emergency Department after being involved in a motor vehicle accident. The patient reports not being able to move or feel his legs. You suspect a spinal cord injury. Which of the following best describes the type of joint found between the bodies of the 4th and 5th thoracic vertebrae?

Correct Answer: C.  Diarthrosis

In general, joints can be classified into two main groups: diarthrosis and synarthrosis.

Synarthrosis are joints that offer little to no movement under normal conditions.

Synarthrosis can be sub-classified as sutures, synchondrosis, or syndesmosis. Syndesmosis (choice E) is a joint where two bones are attached by ligaments but without synovia or articular cartilage.

A symphysis (choice C) is a type of syndesmosis in which a fibrocartilaginous disc is present between the two bones. The bodies of vertebrae are connected by 5 different spinal ligaments as well as a fibrocartilaginous disc.

Sutures (choice B) describe joints of only fibrous connections as seen between certain cranial bones.

Synchondrosis (choice D) describes joints where the connecting material is cartilage, such as the joint between ribs and the sternum.

Diarthrosis (choice A) are true synovial joints whose components always include a connective tissue capsule, a synovial membrane, and hyaline articular cartilage. The joints found between the articular processes of veterbrae are one example.