Types of joints in the human body

Previously, the bones of the lower limbs were described (read more). Now, the different types of joints between the bones of the human body are analyzed.

We analyze the types of joints

A joint is the union of two or more bones (1, 2, 3), which can occur in different ways and through different tissues that keep them together (2, 3), giving the joint its own functions (2).

This explains that in the human body there are different types of joints, which will have more or less mobility depending on the type of joint in question (1, 2, 3).

Types of joints

The different types of joints are distinguished by the way the bones that form them are joined, by the type of tissues that reinforce them, and by the type of movement/s they can perform (2, 3).

Thus, we find that the types of joints are classified according to their capacity for movement (1, 4), according to the planes in which they perform these movements (3, 4), and according to their form of union (2, 3, 4, 5, 6, 7, 8, 9, 10, 11).

According to their capacity for movement, we find 3 types of joints (1, 4, 5, 12, 13):

• Synarthrosis – no mobility.
• Amphiarthrosis – semi-mobile.
• Diarthrosis – mobile.

According to the planes in which they can perform their movements, we find 3 types of joints (3, 4):

• Uniaxial – one plane.
• Biaxial – 2 planes.
• Multiaxial – the 3 planes.

Regarding their form of union, we find 2 large groups, within which several types of joints are encompassed (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 14, 15, 16, 17).

• Synovial.
  • Arthrodia/Plane – non-axial.
  • Hinge/Ginglymus – uniaxial.
  • Pivot – uniaxial.
  • Condyloid/Ellipsoidal.
  • Saddle.
  • Ball-and-socket – multiaxial.
• Solid.
  • Cartilaginous.
    • Synchondrosis.
    • Symphysis.
  • Fibrous.
    • Sutures.
    • Gomphosis.
    • Syndesmosis.

Synovial joints

Of the different types of joints, synovial, or diarthrosis (5) are the most common (2). They occur thanks to an articular capsule, which is composed of a deep synovial membrane that wraps inside a superficial fibrous membrane.

Within this articular capsule, the articular surfaces are covered with hyaline cartilage and are separated by a space called the articular cavity, (2, 3, 5).

The synovial membrane inserts at the edges of the articular surfaces and fills the articular cavity with synovial fluid, lubricating the articular surfaces and facilitating frictionless movements (2, 3, 5).

This membrane also usually forms synovial bursae located between other tissues and tendon sheaths that cover the tendons to reduce friction between different tissues during movements (3).

The fibrous membrane is the continuation of the periosteum (2, 18), which is the layer of connective tissue that covers the bones (except for their articular surfaces) (19).

It is a dense layer (in some parts more than others) of connective tissue that covers the joint, stabilizing it. From the thicker parts, ligaments arise that enhance the stability of the joint (2, 3).

Within some types of synovial joints, there are structures that help joint stability, increase the range of motion, and/or absorb impacts (fibrocartilage discs, fat pads…) (3).

The types of synovial joints allow their bony components to perform different movements (2, 3), which can be performed in one plane (uniaxial joint), in 2 (biaxial joint), or in the 3 body planes (multiaxial joint) (3):

According to their shape, there are up to 6 types of synovial joints (2, 3, 6, 7, 8, 9, 10, 11):

• Arthrodia/Plane.
• Hinge/Ginglymus.
• Pivot.
• Condyloid/Ellipsoidal.
• Saddle.
• Ball-and-socket.

Arthrodial joints

An arthrodial or plane joint is one in which the articular surfaces are flat or slightly concave-convex (2, 4, 6). Thus, they are non-axial joints (4), meaning they do not belong to an axis (20) although they allow sliding movements between their articular surfaces (2, 4, 6).

These slides can be multidirectional (4) but are reduced, thanks to their articular capsule (2) or a ligament (4).

Some types of arthrodial joints are (2, 4, 21):

• Acromioclavicular joint.
• Tarsometatarsal joints (Lis-Franc joint).
• Intercarpal joint.

Hinge joints

Hinge joints (or ginglymus) (2, 3, 8) are uniaxial, as the movements they allow are flexion-extension in the sagittal plane (2, 4, 8). Their articular capsule is thicker medially and laterally to allow these movements, and strong collateral ligaments help fix the articulated bones (2).

It should be noted that in this article we describe a type of joint, whose names “ginglymus” and “trochlea,” in the literature, can be found to refer to this type of joint (2, 3, 8), to an articular surface (2, 8, 22), or to a cartilaginous ring that is the pulley of the superior oblique muscle tendon of the eye (8).

Some types of hinge joints are (2, 4, 23, 24, 25):

• Interphalangeal joints.
• Humeroulnar joint.
• Femoropatellar joint.
• Sternocostal joints (except for the first left and right).

Pivot joints

They are a type of uniaxial joint, which only allow rotational movements. The bony components have a cylindrical shape, one hollow and the other compact that fits into the first (2, 4, 7).

Some types of pivot joints are (2, 4, 26, 27):

• Proximal radioulnar joint.
• Median atlantoaxial joint.
• Subtalar joint.

Condyloid joints

Condyloid/ellipsoidal joints, also called condylarthrosis (4, 9), are biaxial joints between a concave articular surface and a convex surface. They perform flexion-extension movements (sagittal plane) and abduction-adduction (frontal plane) (2, 4, 9), and slightly circumduction movements (circular movement) (2, 4).

However, the knee joint, specifically the femorotibial joint (bicondylar), performs flexion-extension movements (sagittal plane) and internal-external rotation (transverse plane), as long as the joint is in flexion (2, 23).

Some types of condyloid joints are: (2, 4, 23, 28, 29):

• Knee-femorotibial joint (bicondylar).
• Radiocarpal joint.
• Metacarpophalangeal joints.

Saddle joints

Also called sellar joints (4, 10) or saddle joints (2, 4, 10) (due to the shape of their bony surfaces) (2, 4), they are biaxial joints in which the 2 bony elements have a concave articular surface and a convex articular surface that articulate with the opposite (concave-convex-convex-concave) (2, 4, 10).

These joints perform flexion-extension movements (sagittal plane), abduction-adduction (frontal plane), and circumduction without rotation (circular movement) (2).

Some saddle joints are (2, 4, 22, 30, 31, 32):

• Carpometacarpal joint of the first finger.
• Sternoclavicular joint.
• Calcaneocuboid joint.

Ball-and-socket joints

Of all the types of joints, ball-and-socket joints or enarthrosis are the most mobile. In these joints, the bony articular surfaces are one dome-shaped, into which another semi-spherical one is inserted and moves.

They are multiaxial, being able to perform flexion-extension, abduction-adduction, external-internal rotation, and circumduction movements (2, 4, 11).

Ball-and-socket joints are (2, 4):

• Hip joint (coxofemoral).
• Glenohumeral joint of the shoulder.

Solid joints

The types of solid joints are the union of 2 or more bones through connective tissue or cartilage (fibrocartilage), with their capacity for movement being very limited or null.

Within the group of types of solid joints, we find 2 types of joints: cartilaginous joints and fibrous joints (3).

Cartilaginous joints

They are types of joints whose bony elements are joined by connective tissue or cartilage (fibrocartilage) (3).

Their capacity for movement is limited, being able to perform non-axial slides and/or rotations. There are 2 types of cartilaginous joints (2, 3).

Synchondrosis

They are of the synarthrosis type (14), occurring at the ends of long bones during the growth stage (3, 14) between the ossification centers favoring growth.

Therefore, we are talking about the growth cartilage, which ossifies completely when the person reaches their full bone development (2, 3, 33).

Symphysis

Types of joints anphiarthrosis (4, 13), they are resistant joints (2) whose articular surfaces are joined by hyaline (13) or fibrous cartilage, with their range of motion being limited (2, 4, 13).

Some symphyses are (2, 3, 4):

• Intervertebral discs.
• Pubic symphysis.

Fibrous joints

These types of joints are synarthrosis (4, 12) and occur through the union of bony elements joined by fibrous tissue (2, 3, 4, 12). There are 3 types of fibrous joints (2, 3, 4).

Sutures

Of the types of joints according to the capacity for movement, sutures are of the synarthrosis type between the bones of the skull (2, 3, 4, 17). The bones interlock or overlap (2), being joined by the thin sutural ligament (3, 17).

Gomphosis

These types of joints occur between the teeth and the dental alveolus (2, 3, 4) (cavity for the teeth) (36), in which the teeth are fixed by collagen fibers of the periodontal ligament (3).

Syndesmosis

A syndesmosis is a synarthrosis whose surfaces do not have hyaline cartilage and whose union usually occurs by a ligament or an interosseous membrane (2, 16, 22).

This makes this type of joint, although they are synarthrosis, capable of slight movements (2, 22).

They are syndesmosis (2, 3, 4, 16, 37).

• Inferior tibiofibular joint (tibiofibular syndesmosis).
• Radioulnar syndesmosis (between the diaphyses of the radius and ulna bones).

Bibliographic references

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