Osteoarthritis is a degenerative disease that is common and prevalent in middle-aged and elderly people. It mainly attacks joint cartilage and further involves bone, synovial and ligamentous tissues, resulting in joint pain, deformity and dysfunction, which seriously affects the quality of life of middle-aged and elderly people.
It occurs in joints with high load and high activity, such as the knee, hip, spine (cervical and lumbar spine), ankle, hand and other joints. It has been reported that the prevalence of people under 40 years of age is about 5%, the prevalence of people over 60 years of age can reach 50%, and 80% in people over 75 years of age. The prevalence of OA in China is 13% in Shanghai and 38.7% in Beijing, and OA is more likely to affect the walking, stairs and other lower limb functions of elderly patients than other diseases, so the disability rate of the disease can be as high as 53%. Among people over 50 years old, OA ranks second only to cardiovascular disease in terms of long-term disability.
1. Epidemiology
Known high-risk associated factors include.
(1) Age: The incidence of OA increases with age. In the past decade, with the expansion of human activities and the increase in labor intensity, OA has emerged as a younger trend. In some countries and regions, the age group with a high prevalence of OA is no longer older than 60 years old, but 46-56 years old in middle-aged people, and the onset of male rejuvenation is more obvious than in women.
(2) Gender: the incidence of OA is higher in women (2.59/1000) than in men (1.71/1000), and the incidence is significantly higher in postmenopausal women.
(3) Race: The incidence of OA varies among races. It is usually believed that the incidence of Caucasians and Blacks is higher than that of the yellow race, but because of the large population base in China, so the absolute number of OA patients (about 50 million) is higher than in other countries, with the accelerating trend of population aging, the number of OA patients in China will also increase rapidly.
(4) obesity: a European epidemiological survey found that body mass index and the age of the first symptoms of knee OA is negatively correlated. bmi between 20 and 30 people, the age of the first symptoms of knee OA is about 4.5 years earlier than the overall population, the age of the first symptoms of knee OA is about 9.3 years earlier than the overall population of people with a BMI of more than 30. Obesity as a global health problem will further increase the incidence and disability rate of OA.
2.Etiology and pathogenesis
(1) Mechanical injury
Mechanical factors cause degradation of the extracellular matrix and damage to chondrocytes, thus causing degenerative changes in the joint.
(2) Dysregulation of chondrocyte repair
Mechanical, inflammatory, biochemical or immune changes cause apoptosis, necrosis and proliferation of chondrocytes, which can also interfere with the expression of synthetic and catabolic genes, resulting in reduced synthesis or matrix degradation. For example, increased synthesis of chondrocyte proteases and decreased synthesis of protease inhibitors can cause progressive depletion of the cartilage extracellular matrix.
(3) Synovial membrane changes
Synovial membrane has ultrastructural changes, and synovial membrane changes are secondary to articular cartilage changes, and in turn, the inflammatory response of synovial membrane further aggravates articular cartilage destruction, making the disease in a vicious cycle.
(4) The role of enzymes
It has been found that the activity of neutral protease and collagenase is highest at the site of the most severe articular cartilage destruction. These enzymes degrade the proteoglycan and collagen fiber network in the cartilage matrix, causing structural damage to the cartilage, edema, and reduced viscoelasticity, which in turn erodes the subchondral bone and stimulates marginal osteophytes and inflammatory swelling of the synovium.
(5) Immunological abnormalities
Chondrogen is a closed barrier without blood vessels, and cartilage tissue is mostly isolated from the body’s autoimmune surveillance system, which is known as the “hidden antigen” hypothesis.
(6) Cytokines
Cytokines can accelerate the catabolism of cartilage matrix and cartilage degeneration, has been elucidated more than 50 kinds of CK, of which nearly ten kinds have been found to be related to OA by laboratory or clinical.
(7) Genetic susceptibility
A study of a high percentage of families with early-onset severe OA found that the occurrence of OA was associated with autosomal dominant mutations in type II precollagen. However, the relationship between abnormalities in type II collagen and the occurrence of OA in the population as a whole is unclear.
Although many significant medical advances have been made in recent years, and many etiological and pathogenetic hypotheses have been proposed, the exact cause of OA is still poorly understood.
3.Treatment
The principle of treatment is a combination of non-pharmacological and pharmacological treatment, and if necessary, surgery, but there is no radical treatment for the cause of the disease.
Non-pharmacological treatment includes patient education, weight loss, physical therapy, exercises to increase joint range of motion and muscle strength, walking aids, joint puncture and fluid aspiration, etc.
Anti-inflammatory and analgesic drugs can be applied short-term depending on the severity of the patient’s joint pain and swelling; glucosamine and chondroitin sulfate are chondroprotective drugs and can be used long-term; and viscoelastic supplementation therapy can lubricate joints and reduce symptoms. Medication can only relieve symptoms, and there are no drugs that can clearly stop or reverse the progression of the disease.
Joint cavity irrigation can reduce pain, but it is short-lived and has little effect on improving joint function. Younger patients with unicompartmental knee lesions may undergo osteotomy or unicondylar knee replacement, but the lesion will progress and eventually require total knee surface replacement. For patients with end-stage OA, arthroplasty can eliminate joint pain, correct joint deformity, and restore joint function. However, there are many risks associated with the surgery, including infection, and the cost of the surgery is high, imposing a huge financial burden on the individual patient and society.
With the accelerated aging of the population, the incidence of OA is increasing, which seriously affects the quality of life of patients and imposes a heavy medical and economic burden on families and society. Therefore, it is necessary to strengthen the extensive and in-depth research on OA to better solve this problem.