What Is Joint Stability?

The joint cavity is a closed cavity surrounded by the synovial layer of the joint capsule and articular cartilage. There is a small amount of synovial fluid in the cavity, which presents a negative pressure, and has a certain effect on maintaining the flexibility and stability of the joint.

The joint cavity is a closed cavity surrounded by the synovial layer of the joint capsule and articular cartilage. There is a small amount of synovial fluid in the cavity, which presents a negative pressure, and has a certain effect on maintaining the flexibility and stability of the joint.

Joint cavity: A closed, latent cavity surrounded by articular cartilage and the synovial layer of the joint capsule. There is a small amount of synovial fluid in it, which can lubricate the joint and reduce friction. The negative pressure in the cavity is beneficial to the stability of the joint.

Chinese name

Joint cavity stability

Department

Anatomy

Histological anatomy of joint cavity stability :

Joints are an essential element in human activities, and whether a joint is stable or flexible depends on the following factors:

1. The difference between the radians of the two articular surfaces constituting the joint, that is, the radians of the articular surfaces that are anastomosed with each other. The larger the anastomosis, the more stable the joint, and the smaller the anastomotic joint, the better the flexibility of the joint. The arc between the joint surface of the femoral head and the acetabular joint that composes the hip joint coincides with each other at about 180 °, so the stability of the hip joint is good, while the humeral head of the shoulder joint and the glenoid of the scapula are only 75 ° The arcs of the articular surfaces coincide with each other, so the flexibility of the shoulder joint is better, and the stability is poor. In patients in orthopedics, there are often repeated dislocations of the same shoulder joint, even habitual dislocation.

2. Structural characteristics of the articular surface: The shape of the articular surface plays an extremely important role in the stability of the joint. The humerus-ulnar joint formed by the lower end of the humerus and the ulna olecranon in the elbow joint is a flexor joint, that is, a uniaxial joint, which can only perform flexion and extension movements in one direction, which can prevent the elbow joint from moving sideways. Displacement, the joint end has internal and external condyles, such as the internal condyle of the humerus and the external condyle of the humerus. Such a structure can expand the width of the articular surface on the coronary axis, so that the joint has better lateral stability. The acetabulum and the femoral head are closely anastomosed, and a negative pressure is formed in the joint cavity under the stress that separates the articular surfaces, making the articular surfaces attract each other and not easily dislocated.

3. Thickness and tightness of the joint capsule. Generally speaking, the thicker the structure of the joint capsule, the stronger the stability of the joint, and vice versa. The joint capsule of the hip joint is much thicker than the shoulder joint. Therefore, the stability of the hip joint is much better than that of the shoulder joint. The more relaxed the joint capsule, the greater the flexibility of the joint. The shoulder joint is larger and looser than the hip joint capsule, so the mobility of the shoulder joint is also large, and the mobility of the hip joint is smaller than that of the shoulder joint.

To maintain the flexibility of the joint, in addition to its own structure, to maintain proper movement, do not leave the joint in a static state for a long time, the only way to keep the joint flexible.

Joint stability refers to the ability of a human joint to maintain a normal position during rest or movement. Joints are one of the indispensable elements in human activities, and are where the bones are connected. The active joints are divided into two categories, namely cartilage joints and synovial joints. Cartilage joints have no sockets and have a small range of motion, such as the spine. Synovial joints have obvious joint sockets and joint heads, the former being concave and the latter convex, providing a large range of motion.

Joint stability is an important guarantee for normal body movement. If there is damage, especially the ligaments, tendons, and neuromuscular problems that people often hear about, the joints will be unstable, mainly manifested in the relative movement between the joint surfaces beyond the actual normal range, which is often said in our lives Joint looseness, looseness, or even dislocation and dislocation causes the joint to lose its normal function of supporting movement, which will seriously affect people's daily activities.

We often see such examples in life: The shoulder joints of patients with stroke and hemiplegia often have problems such as subluxation or dislocation. This is because the muscles of the affected shoulders atrophy, and the nerves cannot control the muscle contraction to stabilize the shoulders. joint. At the same time, because the arms hang down for a long time, the weights of the joints pull the ligaments and capsules of the joints for a long time, which makes them gradually stretched, unable to restore the original tension and normal position, resulting in joint relaxation and instability.

Factors that cause poor joint stability

There are many risk factors that cause poor joint stability. As we get older, the nervous system responds more slowly, the joints gradually degenerate, and the appearance of arthritis causes inconvenience or pain, causing abnormal muscle strength and joint instability. Due to changes in endocrine factors such as menstruation, the relaxation of joint ligaments in women causes their joint instability to be much higher than in men.

A study in the United States shows that the number of anterior cruciate ligament tears in American women's football players is four times that of male athletes. It is generally believed that the larger the pelvis of the female, the larger the angle of the knee joint buckle, and the weaker the muscle strength of the female than the male, it is bound to increase the risk of knee injury.

Clinical Anatomy of Joint Cavity Stability

Other studies have shown that there is an inseparable relationship between joint stability and osteoarthritis. Osteoarthritis is a degenerative disease of the joint, and the factor of its incidence is generally considered to be the degeneration of the articular cartilage. But with the research on the pathogenesis of osteoarthritis, people realize that the stability of the knee joint also plays an important role in the occurrence and development of the disease.

Take the knee joint as an example. In the past, the measurement of knee joint stability was performed by hand, and the accuracy was not high. It is only suitable for rough examination of patients with ruptured ligaments. With the advent of knee joint stability measuring instruments in recent years, the measurement of joint stability has ushered in a high-precision detection method that can reflect the millimeter-level relaxation of ligaments. Some studies have statistically analyzed the cruciate ligament data of patients and healthy controls, and found that the patient's ipsilateral anterior cruciate ligament is significantly loose compared with the control group and the uninjured anterior cruciate ligament, so the degree of relaxation of the cruciate ligament is stable with the knee Sex is related to the onset of osteoarthritis.

The onset of osteoarthritis and the loss of knee stability is a vicious cycle. In the past, the rehabilitation of knee arthritis mostly focused on pain relief and improvement of joint mobility, while neglecting joint stability. In recent years, the important role of enhancing the stability of knee joints in the treatment of knee arthritis has been gradually realized. Therefore, functional exercises, isokinetic strength training, proprioceptive exercises, weight loss, and increased bone density have gradually been valued by rehabilitation doctors and orthopaedic surgeons. . The study found that muscle strength was significantly improved after exercise therapy and isokinetic training, which could significantly improve joint stability and reduce pain.

Therefore, we must pay more attention to the stability of the joints, and do a good job of protection and exercise. With good joint stability, we can have a healthy body, reduce the risk of osteoarthritis, and provide quality guarantees for daily life and work.