You bend an elbow to pick up a cup, turn your head to check a mirror, or flip open an anatomy chapter and meet three long Latin-flavored words in the first paragraph. Every one of those moments runs through a joint. So what are the types of joints, exactly? Anatomists sort them two ways: by what holds the bones together, and by how much movement the joint allows. Learn both systems and the vocabulary stops looking like a wall of terms.

This guide follows the classification in the OpenStax Anatomy and Physiology 2e textbook, chapter 9, "Joints." It covers what a joint is, the three structural classes, the three functional terms, and the six types of synovial joints, each with an example from the textbook.

In Google Trends data for the US over the past 7 days, top related searches for the seed term "types of joints" were led by "what are joints" with a score of 100, followed by "joint types" (98), "what are the types of joints" (91), "types of synovial joints" (76), "synovial joints" (75), "types of joints in the body" (47), "what is a joint" (36), "fibrous joints" (34), "three types of joints" (33), and "cartilaginous joints" (24). Top scores are relative interest scaled so the top term equals 100; they are not search counts. A rising percentage, where one appears, shows growth in search interest compared with the prior period; every term in this cluster is a top term rather than a rising one. The pattern is plain: people want the basic definition first, then the names of the classes, with synovial joints drawing the most detailed questions.

What is a joint?

Start with the definition. The OpenStax Anatomy and Physiology 2e textbook defines a joint, also called an articulation, as any place where adjacent bones or bone and cartilage come together. That is the whole idea. A joint is not a single structure like a bone. It is a meeting point.

That definition is wider than most people expect. It includes the places that move a lot, like the shoulder, and the places that barely move at all, like the seams between the bones of the skull. If you searched "what are joints" or "what is a joint," that is the short answer: a joint is where bones meet, whether or not anything moves there. For the bones themselves, our guide to what the skeletal system is covers the framework these meeting points connect.

What are the types of joints? The three structural classes

The first way to sort joints is by structure: what fills the space between the bones. OpenStax names three structural classes. This is the answer most people want when they search "three types of joints."

• Fibrous joints: the adjacent bones are united by fibrous connective tissue.
• Cartilaginous joints: the bones are joined by hyaline cartilage or fibrocartilage.
• Synovial joints: the bones do not connect directly. They come into contact within a joint cavity filled with a lubricating fluid.

Notice the logic. Two classes are named for the tissue that bridges the gap. The third is named for the fluid inside the space. If you want to know what fibrous connective tissue, hyaline cartilage, and fibrocartilage actually are as tissues, our explainer on the types of connective tissue walks through them. This piece stays on the joints.

Fibrous joints and cartilaginous joints: the subtypes

Each of the first two classes splits further. OpenStax describes three kinds of fibrous joints:

• Suture: a narrow fibrous joint between bones of the skull. The textbook notes that all the bones of the skull except the mandible are joined to each other this way.
• Syndesmosis: a joint where two parallel bones are united by fibrous connective tissue, such as the radius and ulna of the forearm, or the tibia and fibula of the leg.
• Gomphosis: the specialized fibrous joint that anchors the root of a tooth into its bony socket.

It describes two kinds of cartilaginous joints:

• Synchondrosis: bones joined by hyaline cartilage. The textbook gives the epiphyseal plate, or growth plate, of a growing long bone as a temporary example, and the joints where the ribs meet their costal cartilage as a permanent one.
• Symphysis: bones joined by fibrocartilage. Examples are the pubic symphysis of the pelvis and the intervertebral symphysis, where a pad of fibrocartilage called an intervertebral disc sits between adjacent vertebrae.

The functional terms: immovable to freely movable

The second way to sort joints is by function, meaning how much movement the joint allows. OpenStax uses three terms:

• Synarthrosis: an immobile or nearly immobile joint. The skull sutures are the classic example.
• Amphiarthrosis: a joint with limited mobility. The textbook points to the intervertebral discs and the pubic symphysis.
• Diarthrosis: a freely mobile joint. According to OpenStax, all synovial joints are diarthroses.

The two systems overlap but do not line up one to one. A syndesmosis is structurally fibrous, yet OpenStax classes it functionally as an amphiarthrosis because it allows slight movement. A gomphosis is also fibrous, and functionally a synarthrosis. That is why textbooks list both labels: one tells you what the joint is made of, the other tells you how much it moves.

OpenStax adds one more layer for freely mobile joints: the number of axes they move in. A uniaxial joint, like the elbow, moves in one plane. A biaxial joint, like the knuckle joints of the fingers, moves in two. A multiaxial joint, like the shoulder or hip, moves in three.

Types of synovial joints: six shapes, six examples

Synovial joints get the most detailed questions in the search data, and for good reason. OpenStax lists the parts every synovial joint shares: a joint cavity; articular cartilage, a thin layer of hyaline cartilage over the surface of each bone; an articular capsule that forms the walls of the cavity; a synovial membrane lining the inside of that capsule; and synovial fluid, which the textbook describes as a thick, slimy lubricating fluid.

What separates one synovial joint from another is the shape of the surfaces where the bones meet. OpenStax names six types:

Source: OpenStax, Anatomy and Physiology 2e, section 9.4, "Synovial Joints."

OpenStax also notes that the ball-and-socket joint has the greatest range of motion of the six. The hinge type includes more than the elbow; the textbook also lists the knee, the ankle, and the interphalangeal joints of the fingers and toes.

The bridge: reading joint names like a map

The search data shows people asking the same question several ways: "what are joints," "joint types," "types of joints in the body." The answer comes in layers. Structure first: fibrous, cartilaginous, or synovial. Function second: synarthrosis, amphiarthrosis, or diarthrosis. Then, for synovial joints, shape: pivot, hinge, condyloid, saddle, plane, or ball-and-socket.

Once you have those three layers, any joint name becomes easy to place. Take the elbow. Structurally it is synovial. Functionally it is a diarthrosis. By shape it is a hinge, and by axes it is uniaxial. Four labels, one meeting point, no memorizing required. Run the same drill on the hip and you get synovial, diarthrosis, ball-and-socket, multiaxial.

Our take on joint classification

We like classification systems that explain themselves. This one does. Each label answers a single question: what holds the bones together, how much the joint moves, or what shape the surfaces are.

We think the most useful habit is to stop reading the terms as a list and start reading them as questions. When you meet a joint name you do not know, ask the three questions in order. You will place it faster than any flashcard could.

We also think the overlap between the two systems is the most useful part, not a flaw. A joint can be fibrous and slightly movable at once. Holding both labels in mind is what keeps the vocabulary honest.

Why we carry it at PRSPR

We wrote this anatomy guide as part of our Learn library, and it sits alongside the Inflammation Reset Stack. This article is about how anatomists name and classify joints, nothing more. Here is what the listing states about the stack itself:

• Name: Inflammation Reset Stack - Anti-Inflammatory Bundle.
• Format: a four-product stack.
• What is in it: Sarsaparilla, Magnesium Glycinate, Black Seed Oil (Nigella sativa), and Seamoss Capsules.
• Price: $122.36.

It is made in a GMP-certified facility and third-party batch tested. You can see it with our other sets in the Bundles collection.

See the Inflammation Reset Stack at PRSPR

FAQ

What are the types of joints?

By structure, the OpenStax Anatomy and Physiology 2e textbook names three types of joints: fibrous, cartilaginous, and synovial. By function, it uses three terms: synarthrosis (immobile), amphiarthrosis (limited mobility), and diarthrosis (freely mobile).

What is a joint?

OpenStax defines a joint, or articulation, as any place where adjacent bones or bone and cartilage come together.

What are the six types of synovial joints?

OpenStax lists pivot, hinge, condyloid, saddle, plane, and ball-and-socket joints. Examples include the atlantoaxial joint (pivot), the elbow (hinge), the knuckle joints (condyloid), the base of the thumb (saddle), the intercarpal joints (plane), and the hip (ball-and-socket).

What are fibrous joints and cartilaginous joints?

In fibrous joints, bones are united by fibrous connective tissue; sutures, syndesmoses, and gomphoses are the three kinds. In cartilaginous joints, bones are joined by hyaline cartilage or fibrocartilage; synchondroses and symphyses are the two kinds.