Exercise is good for your health, but you should also protect your knees

This is the 4421st article of Da Yi Xiao Hu

Playing basketball helps improve the body's running and jumping ability, playing football helps to strengthen the leg muscle strength and flexibility, playing table tennis helps to improve the body's coordination ability, doing yoga helps to improve the body's flexibility, and long-distance running and mountain climbing help to improve endurance and cardiopulmonary capacity. These sports are good for health, but at the same time, these sports also require high stability and flexibility of the knees. If the exercise is too intense, it is easy to cause damage to the knee joints.

There is such an example around me. In December last year, one of my high school classmates suddenly stopped and changed direction while playing basketball. The action was too violent, which caused the anterior cruciate ligament of the knee to be torn. He underwent anterior cruciate ligament reconstruction, meniscus repair, patellar bipartite reconstruction and other operations, and according to his description, he was in great pain after the operation and during rehabilitation. In January of this year, with the assistance of a rehabilitation therapist, he began to practice walking. At present, he can walk on crutches by himself, but he can't do more violent movements such as running and jumping, let alone touch the basketball. I feel very sympathetic and regretful about this. There are also many people around me who love sports, including many violent ball sports. I am also a table tennis enthusiast, so I hope that this popular science article of mine can convey some knowledge about how to protect the knees during sports and in daily life, and arouse everyone's attention to the knee joint.

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Why is the knee joint vulnerable to injury?

This has a lot to do with the function and structural characteristics of the knee joint.

Functionally , it is one of the most important joints in the human body, shouldering the dual tasks of weight-bearing and being the movement hub of the lower limbs. It can be easily injured if you are not careful.

Structurally , it is a joint with a more complex anatomical structure. It is a complex trochlear joint with multiple joints and ligaments. The articular fossa is relatively shallow and it mainly relies on the surrounding joint capsule, tendons and ligaments to maintain stability. It spans multiple joints and has many muscles, and is easily affected by other joints.

So, how can we take care of our knees when exercising?

1. Try not to exceed your toes when bending your knees forward to reduce the weight on your knees

Let's first look at a diagram of the knee joint forces in different postures.

According to biomechanical analysis, the load on the knees is almost zero when lying flat; when standing up, the load on the knees is approximately equal to the body weight; when walking on flat ground, the load on the knees is about 2 times the body weight; when going up and down stairs and up and down slopes, it is 3 to 4 times the body weight; when running, it is 4 times the body weight; when playing ball, it is 6 times the body weight; when squatting or kneeling, the load on the knees can reach about 8 times the body weight. It can be seen that when the knees bend forward and exceed the toes, the load on the knees will double.

When the knee joint is under high load, it will increase the friction of the cartilage edge and accelerate the loss of cartilage. Once the cartilage is damaged, the knee joint loses the protection of the cushion, and the bones begin to grind against each other, causing pain. Therefore, when exercising, we should try to avoid bending the knees forward beyond the toes to reduce the load on the knees.

2. Control the degree of exercise

Studies have shown that the risk of knee injury for competitive runners is 13.3%, for recreational runners is 3.5%, and for people who rarely run is 10.2%, which is about three times the risk of knee injury for recreational runners. It can be seen that not exercising can also damage the knees, and proper exercise can actually exercise the knee joints.

During exercise, the fluidity of the synovial fluid in the knee joint increases, the nutritional function is enhanced, and it can strengthen the toughness and muscle strength around the joint, increase the stability of the knee, and slow down the wear of the knee joint. Therefore, when we exercise, we should control the amount of exercise, exercise moderately, step by step, and do it according to our ability, so that the knee joint can be fully exercised while paying attention to avoiding excessive exercise.

3. How to exercise and suggestions for various types of exercise

To protect the knee joint, you must not only move, but also know how to move. It is recommended to choose sports that put less weight on the knee joint, such as swimming, cycling, and brisk walking, and try to avoid sports that put more weight on the knee joint, such as mountain climbing and climbing stairs. We should fully warm up before exercise, which can improve the elasticity and ductility of tendons and ligaments, increase the range of motion of joints, stimulate the secretion of synovial fluid, reduce joint wear, and prevent injuries during exercise. Do not stop immediately after exercise, but take a deep breath and stretch, which will help relax the muscles.

When swimming, backstroke and freestyle are preferred over breaststroke, which places unnecessary stress on the knee joint through shear forces and turning movements. Water jogging with a buoyancy vest is an excellent form of exercise that can be performed with little to no load even in advanced knee osteoarthritis.

When riding a bicycle, the seat should not be too low to avoid bending the knees too much. Also pay attention to the rhythm of muscle force and relaxation when straightening and bending.

In our daily lives, we should also

1. Avoid sitting for long periods of time

Perhaps many people would think, when sitting, the knee joints do not move, so how can they be injured?

This is because sitting for a long time without exercise will cause the thigh muscles to atrophy and cannot help share the pressure of the knee joint well, which will lead to poor stability of the knee joint and accelerated cartilage wear.

When sitting, the knees are in a bent state, the blood circulation at the knees is blocked, the nutrients in the blood cannot be transported better, the nutritional metabolism of the articular cartilage is affected, the synovial fluid is reduced, the aging degree of the knees is increased, and it is more likely to suffer from arthritis.

Therefore, it is best to take time to get up and walk around every half an hour. If you really don’t have time to get up, you should also stretch your legs regularly and do some simple knee protection exercises when sitting.

Here is a simple knee protection exercise: Sitting straight leg raise exercise

Exercise method: Sit on a chair and maintain a good posture, straighten the knee joint of one lower limb, count slowly to 10 seconds, then slowly lower your leg, and repeat 10 times for each leg.

Exercise effect: Seated straight leg raise exercise can effectively enhance the strength of the quadriceps, strengthen the stability of the knee joint, and improve local blood transportation and metabolism, thereby relieving pain and improving the function of the knee joint.

2. Keep your knee joints warm

The knee joint, like other joints in the human body, needs to be kept warm in daily life. From the perspective of traditional Chinese medicine, the pathogenesis of knee joint disease is related to the lack of positive energy in the human body, which allows wind, cold, and dampness to enter the body, leading to stagnation of qi and blood and obstruction of meridians. When many patients with knee arthritis are exposed to cold, their joint pain symptoms will be aggravated, and they will have difficulty walking. Therefore, in daily life, we must keep the knee joints warm to avoid the invasion of wind, cold, and dampness.

3. Choose a pair of comfortable sports shoes

High heels are a major factor in knee injuries in women. Wearing high heels for a long time will not only change the three-point force line structure of the foot, but also keep the entire lower limbs in a state of tension for a long time. Long-term tension and pressure can also lead to degenerative changes in the patellofemoral joint, prematurely trigger knee joint degeneration and aging, and cause knee pain. Therefore, we recommend that you try not to wear or wear high heels less. When wearing high heels, avoid climbing, going upstairs, or squatting.

In addition, whether walking, running, climbing stairs, or playing ball, we should pay attention to wearing a pair of comfortable, elastic, and lightweight sports shoes to reduce the impact and pressure on the knees during exercise. Sports shoes should also have anti-slip function to prevent falls, and the heel of the shoe can be slightly higher than the sole surface by 2-3cm.

4. Control your weight

Studies have shown that the risk of meniscus tears in obese people is nearly 4 times higher than that of people with normal weight, and the risk of high-grade cartilage defects is nearly 2 times higher!

Obesity is the enemy of the knee joint. Overweight people are more likely to have knee pain than others because the extra weight overloads the joints. Losing weight can help relieve knee pain in the long term. Therefore, in daily life, we should control our diet and move our legs, which can both reduce weight and protect our knees.

Exercise is good for your health, but you should also take care of your knees.

Let us exercise scientifically, cherish our knees, and hope that each of us can have healthy knee joints!

Author: Shanghai University of Traditional Chinese Medicine, School of Rehabilitation Medicine

Rehabilitation Physiotherapy

Fan Yicheng 2022401022