World Arthritis Day丨The legs age first, and the legs age in the joints - Talk about "osteoarthritis"

Author: Hu Jingwen, School of Basic Medical Sciences, Three Gorges University

Huang Yiling, Associate Professor, School of Basic Medical Sciences, Three Gorges University

Illustration: Wang Huiping, Hu Jingwen, School of Basic Medical Sciences, Three Gorges University

Reviewer: Hu Huojun, Chief Physician, First Clinical Medical College, Three Gorges University

"Ouch, my legs are starting to hurt again, I can't use my strength, and sometimes they make crackling sounds..." On a rainy day, 70-year-old Grandma Zhang kept complaining at home. To be honest, this was not Grandma Zhang trying to show off her presence in front of her family, but her "arthritis" was at work.

Arthritis is not a specific disease, but a general term. Depending on the cause, there are more than 100 types of arthritis, the most common of which is osteoarthritis. Osteoarthritis is more common in people over 50 years old and can cause joint pain, tenderness, stiffness, joint swelling, limited mobility, joint deformity, etc. It is known as the "disabling killer of middle-aged and elderly people." Let's talk about "osteoarthritis" below.

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1. What is osteoarthritis?

Osteoarthritis is a chronic joint disease characterized by degeneration of articular cartilage and secondary bone hyperplasia, also known as "osteoarthritis", "degenerative arthritis", "proliferative arthritis", "senile arthritis", etc. Osteoarthritis affects articular cartilage or the entire joint, including subchondral bone, joint capsule, synovium and periarticular muscles.

Statistics from The Lancet show that as of 2020, the number of people suffering from osteoarthritis is 595 million, and it is expected that this number will be close to 1 billion by 2050. There are about 133 million people suffering from osteoarthritis in my country. As the aging of the population in my country continues to intensify, the prevalence of osteoarthritis is on the rise.

As the disease progresses, osteoarthritis patients will experience symptoms such as redness, swelling, stiffness, pain, and dysfunction of the joints. In the early stages of the disease, patients only feel mild and intermittent pain in the joints, which improves when resting, but worsens after activity. The pain will also increase when the weather changes drastically. When getting up in the morning, the joints will feel stiff, which can be relieved to a certain extent after activity. If the disease continues to progress, the joints will become swollen or even deformed, bone friction sounds will occur when the joints move, and the joint mobility will decrease. In the later stages of the disease, joint weakness will occur, the legs will be soft or the joints will be locked when walking, the joints cannot be fully straightened or there will be movement disorders, and the patient's movement will be limited.

Osteoarthritis often occurs in the knee joints, hip joints, spine, and distal interphalangeal joints, which have greater mobility.

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2. What are the risk factors for osteoarthritis?

1. Age factor Osteoarthritis is also called "senile arthritis" because age is one of the key factors leading to osteoarthritis. The prevalence of osteoarthritis in people over 60 years old can reach 50%, and the prevalence in people over 70 years old can reach 80%, far exceeding the incidence of cardiovascular disease.

2. Women The incidence of osteoarthritis in women is higher than that in men, which is closely related to their body shape and living habits. Women have weaker muscle strength, ligaments are easily injured, and bones are not easy to recover after being injured. Women who like to wear high heels are also more likely to suffer from osteoarthritis, because wearing high heels can make the soles of the feet lean forward, and the knee joints are in a state of hyperextension, which will accelerate the aging of the knee ligaments, increase the load pressure on the knee joints, and increase the wear of the knee cartilage, which increases the incidence of osteoarthritis. In addition, most women enter menopause after the age of 50, and their estrogen levels drop, and the metabolism of articular cartilage weakens, making them more likely to have bone changes.

3. Overload-level exercise Athletes or people who often climb mountains, climb stairs, kneel to mop the floor, or engage in heavy labor for a long time are prone to osteoarthritis.

4. Obesity Obesity is an important risk factor for osteoarthritis (especially knee osteoarthritis). Body mass index (BMI) is an internationally used indicator to measure the degree of fatness and thinness of the human body and whether an individual is healthy. Its value is weight (kg) divided by the square of height (m), and the normal range is 18.5-23.9. It is reported that the incidence of knee osteoarthritis in obese people aged ≥40 years (BMI ≥30) is about three times that of people with a healthy weight. For every unit increase in BMI, the incidence of osteoarthritis will increase by 15%.

3. How does osteoarthritis occur and develop?

To understand the pathogenesis of osteoarthritis, we must first understand the normal joint structure. The basic structure of a joint consists of three parts: the articular surface, the joint capsule, and the joint cavity. The articular surface is the contact surface of each related bone, usually one convex and one concave, covered with articular cartilage, which can reduce the friction of the articular surface and cushion shock and impact. The joint capsule is divided into an outer layer of fibrous membrane and an inner layer of synovial membrane, which can secrete synovial fluid to lubricate the joint, protect the articular cartilage, and prevent internal wear of the joint. The joint cavity refers to the closed cavity between the synovial layer of the joint capsule and the articular cartilage (with a small amount of synovial fluid), which is under negative pressure and can maintain the flexibility and stability of the joint.

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In the first stage of osteoarthritis, the articular cartilage begins to degenerate and may turn pale yellow and lose its luster. Then the surface of the cartilage becomes rough, and it softens locally and loses its elasticity. When the joint moves, it wears away and the cartilage may break and peel off, forming loose bodies in the joint.

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In the second stage, the synovial fluid in the joints will decrease significantly and its lubricating function will gradually be lost. The cartilage will become fibrotic due to wear and erosion, and the joint structure will also change.

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In the third stage, the cartilage degenerates severely, its lower end is almost exposed, bone spurs appear at the ends of the bones, and subchondral cysts, muscle atrophy, etc. follow.

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4. How to prevent osteoarthritis?

To prevent the occurrence of osteoarthritis, pay attention to the following points.

(1) Exercise appropriately. Avoid sitting for long periods of time. Do appropriate exercise. Warm up before exercise and choose a form of exercise that suits you, such as swimming or walking. Avoid exercises that cause great wear and tear on joints, such as mountain climbing or climbing stairs. When lifting heavy objects, take the correct posture. Do not bend over to lift heavy objects. Instead, squat down first, straighten your back, and lift the object with your legs.

(2) Keep warm. Try not to wear short skirts or shorts in summer, and try not to expose your joints to cold air from air conditioners. Wear knee pads in winter to prevent your knees from getting cold.

(3) Get rid of some bad habits, such as crossing your legs and cracking your knuckles.

(4) Maintain a healthy diet, consume appropriate amounts of foods rich in protein, calcium, and glucosamine (such as dairy products, soy products, eggs, fish, nuts, kelp, etc.), and reduce the intake of high-cholesterol foods (such as animal offal, seafood, etc.).

Only when your joints are worry-free can you show your full potential.

References

[1] Chen Xiaoping, Wang Jianping, Zhao Jizong. Surgery[M]. 9th edition. Beijing: People's Medical Publishing House, 2018.

[2]GBD 2021 Osteoarthritis Collaborators. Global, regional, and national burden of osteoarthritis, 1990-2020 and projections to 2050: a systematic analysis for the Global Burden of Disease Study 2021[J]. Lancet Rheumatol, 2023, 5(9):e508-e522.

[3] Jia Di, Wei Jiajia, Duan Xiuquan, et al. Analysis of the disease burden of osteoarthritis in China from a global perspective [J]. Modern Preventive Medicine, 2022, 49(13): 2312-2316.

[4] Zhao Yanping, Lin Zhiguo, Lin Shudian, et al. Diagnosis and treatment guidelines for osteoarthritis[J]. Chinese Journal of Internal Medicine, 2022, 61(10):1136-1143.