What Is a Synovial Joint?

Synovial joints are often simply referred to as joints. They are composed of two or more bones, with a gap between the opposite bone surfaces. They are only connected by the surrounding fibrous connective tissue membrane. Synovial joints are the main form of bone connection and have great mobility.

Synovial joints are often simply referred to as joints. They are composed of two or more bones, with a gap between the opposite bone surfaces. They are only connected by the surrounding fibrous connective tissue membrane. Synovial joints are the main form of bone connection and have great mobility.

Chinese name

Synovial joint

Foreign name

synovial joint

Short name

joint

Tissue membrane

Fibrous connective tissue membrane

Synovial joint concept

Joints refer to the joints between bones. The joints connected to bones can be divided into two types due to the different functions of bones in various parts of animals. Fixed joints (bone sutures): Bone and bone are tightly connected by dense fibrous connective tissue, such as between bone fragments of the skull. Movable joints: One of the joint surfaces where the two bones are in contact is generally convex and the other is concave, so that the shapes can adapt to each other. There is a thin layer of smooth articular cartilage on the articular surface. The two joints are full of elasticity, reducing friction, and cushioning shock and vibration during exercise.

Basic structure of synovial joint

Although there are many kinds of joints in the human body, the basic structure is nothing more than articular surface, joint capsule and joint cavity.

1. Articular surface: The smooth surface where the bones contact each other is called the articular surface. The articular surface is covered with a layer of cartilage called articular cartilage.

2. Joint capsule: It consists of connective tissue, which is attached to the bone surface around the joint surface. It can be divided into two layers, the outer layer is a fibrous layer, which is composed of dense connective tissue; the inner layer is a synovial layer, which is composed of a thin layer of loose connective tissue, which can secrete synovial fluid and play a lubricating role.

3, joint cavity: is the sealed space between the articular cartilage and the joint capsule. Contains synovial fluid to reduce bone-to-bone friction

4, articular cartilage: reduce friction between bones.

5, joint head: fasten with the joint socket, exercise.

6. Articular fossa: fasten with the joint head for exercise. Basic lesions of the joint.

7, zygapophyseal joints:

Also known as facet joints, it consists of the articular surfaces of the adjacent upper and lower cervical vertebral joint processes. The bilateral articular process joints, together with the vertebral body and disc in front, form the intervertebral joints of the cervical spine, and jointly maintain the stability of the cervical spine. In recent years, anatomical and biomechanical studies have shown that joint injury and degeneration are one of the most common causes of chronic neck pain, which is known as the engine of chronic neck pain. Cervical spine articular hyperplasia is also an important cause of cervical spine instability and nerve root compression.

The area and shape of the joint is closely related to the stability of the joint. When the upper and lower articular surfaces are adapted, the larger the area of the articular surface, the smaller the pressure and the stress during exercise, and the more stable the joint. Yoganandan et al. Used microdissection techniques to cut fresh specimens of adult cervical spine, and analyzed the width of joints, cartilage thickness, and joint space. The thickness is 0.4 ± 0.02mm for women and 0.5 ± 0.03mm for men. The authors speculate that since the cartilage thickness of women is smaller than that of men, their joints are more likely to degenerate under trauma and long-term physiological load, leading to joint disorders. The width of articular cartilage surface gradually decreased from top to bottom, C1 ~ C2 was 17.4 ± 0.4mm, and C7 ~ T1 was 11.3 ± 0.3mm. The shape of the articular surface (width / height ratio) C3 is round, C4 and C5 gradually change to horizontal ellipse, and C7 and T1 are long and horizontal. This change may be related to adapting to the physiological movement of the cervical spine. The bottom and the bottom are adapted to change with different spinal segments to facilitate spinal movement.

Basic synovial joint disease

1. Joint swelling is usually caused by congestion, edema, bleeding, and inflammation of joint fluid or joint capsule and surrounding soft tissue.

2, joint destruction of articular cartilage and osteoarticular bone below the bone was invaded and replaced by pathological tissue.

3. In the early stage of joint degeneration, articular chondrocytes degenerate, necrotize, and dissolve, and gradually be replaced by fibrous tissue or fibrocartilage.

4, joint rigidity can be divided into bony rigidity and fibrous rigidity.

5. Dislocation and dislocation of joint end of joint. Divided into complete dislocation and subluxation.