The Six Types of Synovial Joints: Examples & Definition

Why Bodies Move

Take a moment to move your arm up and down at the elbow. How is this possible? Most people don’t give it much thought; however, the action of moving your arm in this manner would not be possible without specialized structures called synovial joints.

Synovial joints, sometimes called diarthrosis, are the most movable type of joint in the body. Joints are formed where bones come together. In this lesson, we’ll explore the six types of synovial joints and discuss their functions. Without these joints, your body couldn’t move like it does today.

Six Synovial Joints

To guide you through the process of learning about these joints, take a look at this illustration. We’ll refer to it during our lesson:

Synovial joints and the human body

As shown on this illustration, the six types of synovial joints include the pivot, hinge, saddle, plane, condyloid, and ball-and-socket joints. These joints are found throughout the body; however, some locations serve as better examples than others. To begin our investigation, let’s focus on the pivot joints.

The pivot joint, also known as rotary joint, allows for rotational movement. Pivot joints are indicated as joint letter A on our illustration. This type of joint can be found between your neck vertebrae. For instance, when you turn your head side-to-side, it’s due to the rotary motion permissible in pivot joints.

Next, let’s focus on hinge joints, shown as letter B on the diagram. Hinge joints are the synovial joint type referred to in our introductory section. These joints can be found between your upper and lower arm bones, otherwise called your elbow, as well as your ankles, fingers, toes, and knees.

Hinge joints operate just like the hinges on a door. They allow for a swinging motion, where bones can either flex toward one another or extend apart. Twisting or overextending a hinge joint can result in injury. If you’ve ever twisted your knee or rolled your ankle, it’s likely that a hinge joint was forced to move in a manner it shouldn’t have.

Saddle joints, indicated by letter C in our illustration, are similar to hinge joints but provide more range of motion. In the case of a saddle joint, the bone sitting on the saddle can move in an oval shape relative to the other bone. Our thumb is a classic example of a saddle joint in action. Thumbs can move using a hinge-like motion but can also rock side to side. This is because of a saddle joint. In fact, it’s the saddle joint that makes our thumbs opposable, a trait that allows us to firmly grasp objects with our hands.

Plane joints, sometimes called gliding joints and shown as letter D on the diagram, are probably the most difficult joint type to visualize. They are usually associated with the small bones of your wrists and ankles. In this type of joint, bones slide along beside one another. This allows for movement in many directions, hence the flexibility of your wrists. Here is a picture highlighting the location and type of bones associated with plane joints in your wrist.

Plane joints

Next, we have the condyloid joints, indicated by letter E on our illustration. These joints form where the head of one or more bones fits in an elliptical cavity of another. You’ll find this type of connection in your wrist where it connects the radius, or lower arm, and carpal, or wrist, bones.