Knee osteoarthritis, referred to as koa, is a chronic degenerative disease that often occurs in the middle-aged and elderly. It is mainly characterized by degeneration, destruction and hyperosteogeny of articular cartilage. Its clinical manifestations are swelling and pain of knee joint and limited activity, and even joint deformity in severe cases. There are many patients with koa in China. The latest large-scale epidemiological survey shows that the overall prevalence of symptomatic koa among middle-aged and elderly people over 45 years old in China is 8.1%, including 10.3% for women, 5.7% for men, and even 13.7% in specific areas.

At present, there is no effective cure for koa, and its treatment strategy is mainly limited to drug treatment and surgery. For the former, although NSAIDs can effectively relieve pain, they can not delay or prevent the degeneration and necrosis of articular cartilage from the pathogenesis; In addition, a large number of randomized controlled clinical trials have shown that long-term use of NSAIDs will increase the risk of gastrointestinal bleeding, adverse cardiovascular events and death.

Although artificial joint replacement is an important method for the treatment of end-stage knee osteoarthritis, it is not suitable for young patients due to the limitation of prosthesis life; In addition, complications such as postoperative persistent pain and prosthesis revision will also bring huge physical pain and heavy economic burden to patients.

In recent years, the gradual rise of exercise therapy provides another idea for the treatment of KOA. A large number of evidence-based medical evidence shows that exercise therapy can effectively alleviate joint pain, improve knee function, and delay the time of end-stage surgical intervention. It is a safe and effective conservative treatment. Many academic institutions at home and abroad, such as the American Society of Rheumatology, the British Orthopaedic Association and the branch of orthopaedics of the Chinese Medical Association, have issued guidelines to incorporate exercise therapy into the first-line treatment of osteoarthritis.

Treatment of knee osteoarthritis by water exercise

Underwater exercise therapy is a new type of exercise therapy based on the effect of buoyancy and fluid resistance on human body. Usually, the treatment water temperature is controlled at 32 ℃ ~ 36 ℃. The benefits of water sports are:

① Promote blood and lymphatic circulation, alleviate the adhesion of fibrous tissue inside and outside the joint, and repair the damaged joint to a certain extent;

② Reduce the stress burden of joints, relax muscles, and relieve the pain and stiffness of skeletal muscle system;

③ Water itself is a good medium for hyperthermia therapy. This method has the dual functions of exercise therapy and hyperthermia therapy.

It is found that water exercise therapy can alleviate joint pain, improve knee function, and improve patients’ quality of life and mental health in a short time; However, this effect was not observed in the long-term (6-month) follow-up. Therefore, medical workers can choose water treatment as the first way in the long-term exercise treatment plan.

Training approach of underwater exercise therapy

Muscle strength training:

The change of muscle strength is of great significance in the course of KOA. On the one hand, the decrease of muscle strength reduces the strength of soft tissues such as tendons and ligaments around the knee joint, resulting in joint instability, resulting in abnormal stress distribution on the surface of tibiofemoral joint and patellofemoral joint, which will aggravate the progress of OA. On the other hand, due to disuse atrophy of muscle tissue, the strength of extensor and flexor muscles in patients with koa decreased significantly, forming a vicious circle. Therefore, strengthening muscle strength training can stabilize the stability of knee joint to a certain extent, change the stress distribution of tibiofemoral joint and patellofemoral joint surface, so as to alleviate the pain of affected knee and improve the function of knee joint.

The main parts of muscle strength training include quadriceps femoris, hamstring and hip abductor and adductor muscles, among which quadriceps femoris muscle strength training is the most widely used. It is reported that the quadriceps femoris muscle strength of patients with koa can decrease by 10% ~ 60%, and quadriceps femoris muscle strength training can reduce the adduction torque of the knee joint, thereby reducing the load of the medial compartment of the knee joint and delaying the occurrence and development of osteoarthritis.

In addition, foreign researchers have found that quadriceps femoris muscle strength training can also reduce the sensory motor impairment of patients. The researchers selected 30 patients with koa and performed quadriceps femoris muscle strength training for 12 weeks. The results showed that the pain and function of the affected knee were significantly improved. Considering that the decrease of quadriceps femoris strength will be accompanied by the weakening of hamstring strength, some researchers believe that maintaining the appropriate ratio of hamstring strength to quadriceps femoris strength is very important to maintain the stability of knee joint.

As for hip abduction and adductor group training, because there are disputes about the changes of hip adductor group muscle strength in patients with knee osteoarthritis, the rationality of this method in principle needs to be confirmed by further research, and it is rarely used in clinic.

According to the way of muscle contraction, muscle strength training can be divided into isometric contraction training, isotonic contraction training and isokinetic contraction training.

① Isometric contraction training: there is tension when the length of muscle fiber does not change. Therefore, isometric muscle strength training is not accompanied by joint activity. It is a kind of static training.

For the elderly and patients with weak muscle strength around the knee, relatively obvious pain or more joint cavity effusion, isometric muscle strength training can effectively alleviate joint pain and prevent disuse atrophy of muscles. However, considering the lack of joint activity in the training process, the effect of isometric contraction training in improving neuromuscular control is not ideal, which needs to be combined with other muscle strength training methods.

② Isotonic contraction training: muscle contraction exercise under constant resistance load, so the muscle tension remains unchanged throughout the exercise process. On the one hand, isotonic muscle strength training can make muscle fibers thicker and hypertrophy, effectively improve muscle atrophy, and then enhance muscle strength and restore endurance level; On the other hand, isotonic muscle strength training is mostly arranged after isometric muscle strength training. The combination of the two can more effectively improve muscle strength and muscle function. However, due to weak local muscle strength, patients in acute stage often have compensation of strong muscle groups in the process of training, resulting in unbalanced muscle strength training, so it is not suitable for isotonic muscle strength training.

③ Isokinetic contraction training: it is a dynamic muscle strength training method. By providing muscle strength training at different speeds, this method allows the muscle to always bear the maximum resistance and produce the maximum muscle strength in the whole range of activity. Therefore, it has the advantages of isometric contraction and isotonic contraction. In addition, the training technology can adjust the resistance according to the patient’s muscle strength level, fully consider the individual differences of patients, and has good safety.

Joint range of motion training:

Koa patients often have different degrees of fibrous tissue contracture and scar adhesion inside and outside the joint, which will lead to joint stiffness and reduction of joint range of motion. Therefore, joint range of motion training is a training method to alleviate the pain symptoms and improve the living ability by alleviating the stiffness of the affected knee and improving the joint range of motion.

For patients who are generally in good condition and can complete some active activities, they are encouraged to carry out active exercise activities. Through the gradual axial movement of the joint, the patient can pull the tissues around the joint, such as muscles and tendons, so as to improve the range of motion of the joint. For patients who cannot perform active activities, passive muscle contraction caused by external forces (self healthy limbs, others’ assistance, therapeutic instruments, etc.) can be used to realize joint range of motion training.

Clinical effect of exercise therapy

The clinical efficacy of exercise therapy mainly includes: relieving joint pain, improving knee function and improving quality of life. Some researchers pointed out that the pain relief effect of exercise therapy decreased slightly 2 ~ 6 months after training, but the effect of exercise therapy was still significant in improving knee function. Therefore, exercise therapy to relieve joint pain is a short-term effect, and the effect is not significant after 6 months of treatment; However, long-term adherence to exercise therapy is helpful to restore and improve knee function, and then improve the quality of life of patients.

expectation

As a safe and effective physical therapy, exercise therapy has been widely used in the first-line treatment of KOA. More and more evidence shows that, in addition to muscle strength training, which is more studied and widely used, joint range of motion training, aerobic exercise, water exercise and other forms of exercise therapy can also effectively alleviate joint pain, improve knee function and improve the quality of life of patients.

At present, water sports and other sports treatments also have many problems:

① The stage changes of patients with osteoarthritis and the differences of basic motor ability were not fully considered;

② Most of the existing clinical guidelines do not have unified standards and norms for the design of movement details, specific forms, intensity and course of treatment of exercise therapy. Inappropriate exercise may aggravate the original symptoms and even cause irreversible deformities;

③ Related research design and quality control are diverse, and some trials have some defects in the selection of standard control, so the research heterogeneity is high.

To sum up, we should fully consider the differences of physiological characteristics of different patients, evaluate and monitor their health status, and formulate safe and effective personalized “exercise prescription”, so as to maximize the benefits of exercise therapy while avoiding relevant side effects and adverse events.