What is osteoarthritis? Osteoarthritis, also called degenerative arthritis, or OA for short, is the most common form of arthritis and is one of the most common and prevalent diseases among middle-aged and elderly people. Joint pain after activity is one of the most prominent symptoms. Epidemiological statistics show that 37% of adults have osteoarthritis of the hands or feet, and 38% of adults have osteoarthritis of the knee. more than 80% of people over 65 years of age suffer from different degrees of osteoarthritis, and the prevalence gradually increases with age. With the aging process in the city, more and more elderly people are suffering from osteoarthritis. Osteoarthritis not only brings them physical pain, inconvenience and even disability, but also increases the burden for families and society, which seriously affects the quality of life of middle-aged and elderly people. Caring for the elderly and paying attention to joint health is our duty as children and deserves the attention of the whole society.
Why does osteoarthritis occur? Scientists believe that osteoarthritis may be caused by a combination of genetic abnormalities and joint damage, with progressive cartilage loss in damaged joints. Osteoarthritis is a chronic disease that involves the cartilage and bone of the joints. It is traditionally thought to be due to joint wear and tear, but other factors such as congenital deformities, trauma, and metabolic diseases can also contribute to osteoarthritis. Patients typically experience swelling, stiffness, pain, and worsening of symptoms with daily activities. Subsequently, the subchondral bone grows, causing joint inflammation, ligamentous laxity, and a decrease in associated muscle strength. Patients develop pain with joint movement. Osteoarthritis occurs in all vertebrates except humans, such as dolphins, whales, and dinosaurs that have disappeared for many years. The biological factors that cause cartilage degeneration in osteoarthritis are still unclear, and many experts believe that there is a genetic predisposition to osteoarthritis and that cartilage degeneration is likely to occur when a joint is damaged. The age of the chondrocytes is another factor that limits the repair of cartilage damage in joints. When chondrocytes age, they lose the ability to repair cartilage, which is of great significance in the osteoarthritic disease process. Some studies have reported a high correlation of osteoarthritis between parents and children, or between siblings. More than 50% of patients with osteoarthritis in the finger and hip joints have a genetic component, and a slightly lower percentage in the knee joint. However, recent studies have suggested that the inflammatory response may exacerbate osteoarthritis and be associated with a slow progression of the disease. In 30% of patients with osteoarthritis, there is evidence of an inflammatory response. The inflammatory response referred to here is not caused by an infection such as a bacterial microorganism as commonly thought by the general population, but rather a sterile inflammatory response mediated by inflammatory factors. Osteoarthritis caused by joint injury does not appear until several years after the joint injury. Fourteen percent of patients with a history of joint injury at a young age develop osteoarthritis at age 65, whereas only 6% of patients without a history of early knee injury develop osteoarthritis at age 65. Patients with a knee injury were five times more likely to develop osteoarthritis than those without a knee injury, and patients with a hip injury were three times more likely to develop osteoarthritis than those without a hip injury. Effective ways to prevent osteoarthritis are surgical repair of knee ligaments, meniscus and cartilage damage and rehabilitation. Other possible causes of osteoarthritis: blood disorders, such as hemophilia; ischemic necrosis of the femoral head, which may block the blood supply near the joint; persistent infectious joint disease; chronic gout, pseudogout or rheumatoid arthritis; and iron deposits in the joint, such as hemochromatosis.
What are our joints like? Joints are flexible, stable, and provide support and protection for the limb. These functions are essential for everyday activities and are performed primarily by specific parts of the joint: the synovium and cartilage. The synovium, a membrane that surrounds the entire joint, is filled with synovial fluid and provides nutrients and oxygen to the cartilage; the cartilage, which is slippery, wraps around the end of the bone. Cartilage is one of the few tissues in the body that does not have its own blood supply and has many important components. Chondrocytes: are the most basic component of cartilage and play an important role in its function. Water: Cartilage has a high water content, but it decreases with age. In young people cartilage is 85% water, while in older people it is 70% water. Proteoglycans: are the large molecules that make up cartilage and can bind with water to maintain a high water content in cartilage. Collagen: is the key protein in cartilage that forms a mesh structure to support the joints and keep them flexible. The mesh structure of collagen and proteoglycan-bound water form an elastic slip cushion within the joint, providing a cushion for bone-surface to bone-surface collisions during joint movement. The fluid in the synovial membrane provides nutrition and oxygen to cartilage that has no blood supply.
How does osteoarthritis occur? The first step is cartilage degeneration. Although the process is slow, osteoarthritis begins when the cartilage in the joint degenerates. Early on, the cartilage surfaces and even the synovium become inflamed and swollen, cartilage nutrients are lost, and cracks and pores appear on the cartilage surfaces. As the disease progresses further, the cartilage becomes less elastic and less lubricated, making it more susceptible to damage from repeated activity or trauma. Finally, with extensive cartilage damage and no cartilage protection on the bone surfaces within the joint, osteoblasts may develop reactive proliferative growth and form dense bone plates in areas without cartilage protection. At the edges of the joint, a bone flap may form where new chondrocytes may proliferate and grow abnormally.
Where does osteoarthritis occur? Unlike other arthritis (such as rheumatoid arthritis), osteoarthritis is not a systemic disease and does not spread throughout the body, affecting only one or a few joints. Osteoarthritis commonly affects the joints of the knee, hip, hand, foot or spine, and sometimes the wrist, elbow, shoulder and temporomandibular joints. In the common knee lesion, which occurs in the weight-bearing area of the knee, there is usually pain with movement of the knee, sometimes with a grinding sound or a feeling of interlocking jams. Pain may also be experienced when walking up and down stairs or standing up from a chair. Knee instability may occur when the knee joint becomes enlarged and swollen. Pain in the groin area, inner thigh or outer hip may be felt when the hip joint is diseased. It usually affects the mobility of the joint (especially when rotating the hip). Slight rotation of the damaged joint during walking can reduce the pain, so it can lead to walking with a limp. The pain may radiate to the knee joint and affect the doctor’s diagnosis. In the spine, pain and stiffness in the neck and lower back can occur, as well as pain when nerves are compressed, and further numbness and muscle weakness in the limbs can occur.
What are the symptoms of osteoarthritis? Symptoms of osteoarthritis usually appear gradually over many years, and patients under the age of 40 usually have no symptoms at all. The most common symptom is joint pain. It worsens with increased daily activity and is relieved with rest. At first it occurs only when walking up and down stairs or hiking, but as the disease progresses, joint pain can occur even at rest. Pain is often accompanied by joint stiffness and decreased mobility. In the early stages, it is often mild, with joint immobility felt only in the morning or after sitting for a long time, and can recover with activity. Episodes may come and go, and may be relieved with proper rest. As the disease worsens, joint mobility continues to decrease, making it difficult to squat and eventually leading to loss of joint function. The pain worsens in wet weather. Some patients experience muscle spasms and tendon contractures. Many other conditions can manifest with joint pain. Some are due to poor sleep posture, but some cancers may have similar symptoms to osteoarthritis. Other conditions that cause joint pain are physical injuries, infections, tendinopathies and poor blood supply, and some genetic conditions can also affect the joints. If symptoms similar to osteoarthritis occur, you need to see a doctor promptly for a clear diagnosis and prompt treatment.
What are the conditions that increase the risk of osteoarthritis and that we need to be aware of? Gender: Osteoarthritis is more common in men (and less common in younger people) before the age of 45. After the age of 55, it is more common in women. The incidence of osteoarthritis is 33% in women and 25% in men. Also women are less likely to be seen for pain, and differences in pain sensitivity between men and women may be related to biopsychosocial factors. Education: The lower the level of education, the higher the incidence of osteoarthritis. In the 2000 study, the incidence of osteoarthritis was found to be 41% among those with less than a high school education, compared to 21% among college graduates. This may be related to the different occupations held by these populations. Ethnicity and genetic factors: The incidence of osteoarthritis varies by ethnicity. In the United States, the incidence of the disease is higher in Caucasians and Blacks than in Hispanics and other ethnic groups. Also, there are ethnic differences in the joints involved in osteoarthritis. Asians are more likely to have knee osteoarthritis, which is at the same risk as spondyloarthritis, and slightly less likely than whites to have hip osteoarthritis. Physical and anatomical factors: Many people have abnormal joint anatomy, for example, joint surface mismatch may lead to abnormal long-term joint stresses that can cause joint damage; unequal lower limbs or tilted legs may lead to gait abnormalities that can predispose to osteoarthritis. Some studies have found that knee arthritis may occur in cases of inversion or valgus, commonly known as “rotundity” or “X-shaped legs”. Obesity: Obesity is generally defined as being more than 20% of the standard body weight. Obese people (especially women) are more likely to develop osteoarthritis, and osteoarthritic lesions progress more quickly. However, obesity does not only increase the incidence of osteoarthritis in the knee and hip joints, but also in the finger joints. Some studies have found that obesity may induce a certain inflammatory response, which is a major factor in age-related diseases such as osteoarthritis and heart disease. Therefore, proper weight loss and control can be helpful in preventing osteoarthritis. Work and leisure activity factors: Injuries may trigger osteoarthritis, so those who use more muscles and joints in their work and activities have a higher risk of developing osteoarthritis. High-risk work populations Some jobs require repeated high-intensity movements (such as weighted squats or kneeling) that can lead to joint cartilage damage. Studies have found that people who squat or kneel for more than an hour are at high risk of developing osteoarthritis of the knee. These activities need to be avoided as much as possible in daily activities. Exercise: There is debate as to whether or not you should exercise for osteoarthritis. However, it is important to avoid sports that have high risk factors for osteoarthritis, such as activities that require repetitive joint movements or that place a heavy load on the joints. Examples include soccer, rugby, and baseball. The incidence of osteoarthritis is less common in marathon runners. Studies have found that proper running promotes cartilage health because the rhythmic squeezing of cartilage helps it to eliminate metabolites and absorb nutrients. In conclusion, moderate, rhythmic activity is beneficial and does not increase the risk of osteoarthritis, and a 2006 study of middle-aged adults found that recreational weight-bearing exercise (such as slow walking and jogging) did not affect the development of osteoarthritis. However, muscle wasting and weight gain associated with physical inactivity are risk factors for osteoarthritis.
[Chinese Orthopedic Sports Medicine Network Fudan University Sports Medicine Center] Reprinted with permission from: Fudan University Sports Medicine Center Chinese Orthopedic Sports Medicine Network