The so-called “weak legs”, also known as “weak legs”, “weak knees” are describing a symptom that is normal walking or when walking up and down the stairs, suddenly feel that the knee joints can not eat the strength, leg weakness, and want to kneel down the feeling of phenomenon. The feeling of wanting to kneel down, and sometimes it will be accompanied by severe pain and the phenomenon of really falling down. Most of the patients can’t tell whether it’s the weakness first and then the pain, or the pain first and then the weakness. What’s going on here? Is it calcium deficiency? Today to help you solve this mystery. Not the same as young people in strenuous exercise after the kind (such as long-distance running, playing soccer) accompanied by muscle aches and pains of weakness, that belongs to the loss of excessive body fluids and not timely replenishment of electrolyte disorders caused by the general after rest and replenishment of electrolytes will soon be restored, and middle-aged and elderly people this “soft legs” is the soft tissues around the knee by the pain of the stimulation, sudden spasms caused by the pain. Stimulation, sudden spasm caused by common causes include: 1, joint sports injuries meniscus injury is the most common kind of injury, in the lower limb weight bearing, foot fixed, the knee joint slightly flexion, suddenly excessive internal rotation or external rotation of the knee (such as badminton, basketball, players in the attack and defense often occurs), it may cause meniscus tear. Meniscus injury will have obvious walking flat road playing soft, and sometimes there is joint pain, activity limitation and activity popping and so on. Next is the knee ligament injury, knee joint microflexion stability is relatively poor, at this time, if the sudden external force caused by external or internal rotation, it may cause medial and lateral collateral ligament and cruciate ligament injury. This may cause instability of the knee joint and the feeling that the injured leg is not as strong as it used to be. Obviously feel the injured leg is not strong, walking soft more often, the knee joint has the feeling of wrong movement, and part of it will be swollen. 2, chronic joint disease when due to trauma or long-term friction caused by fat pad congestion, hypertrophy and inflammation, and patellar ligament adhesion occurs, fat pad strain occurs, so that the knee joint activities are limited. This condition mostly occurs in people over 30 years old who often walk, hiking or squatting exercise more frequently. Patients may feel pain and tenderness in the knee joint, and the pain worsens when fully extended, but joint movement is not restricted, and the symptoms are obvious after exertion. Chronic synovitis and abnormal hypertrophy of the synovial folds of the knee joint due to trauma or overstrain can also cause “synovial inlay”, i.e., the synovial membrane floating in the joint cavity like watercress is suddenly pinched between the joints, and at the same time, a large amount of fluid is generated, which makes the patient feel that the knee joints are tender, painful, swollen, and painful, and even interlocking symptoms occur! The patient may even experience interlocking symptoms, which may affect normal activities. 3, degenerative changes in the knee joint osteoarthritis is mostly seen in middle-aged and elderly women, there will be osteophytes, which is often referred to as long “bone spurs”, cartilage degeneration will produce free bodies, when these inflammatory factors stimulate the soft tissues around the knee, the muscles will be sudden spasms, resulting in joint tenderness, and some active joints will be friction sound. In severe cases, the knee may develop an inversion deformity and medial pain. There is also a kind of cartilage lesion between the patella and femur that occurs in young people, i.e. “chondromalacia patella”. As the cartilage surface of the patella becomes uneven, sometimes accompanied by congenital dislocation of the patella, it will cause premature degradation of the cartilage and defects, which will lead to symptoms of tenderness in the knee. If one side or both sides of the limp occur frequently, it is necessary to go to the hospital for examination. After excluding the limp caused by cerebrovascular accident, hemiplegia, muscle strength decline, etc., it is most likely that it is the above mentioned bone and joint problems. It is expected that the cause of the problem will be clarified through physical examination, radiographs, and even MRI. If the diagnosis is still not clear, there is now another reliable diagnostic and treatment technique – arthroscopy, because the lens of arthroscope is very small and connected with optical fiber. Under anesthesia only, a very small incision can be made to insert into the joint cavity for observation and direct visualization of the lesion, making the diagnosis of intra-articular injuries and diseases more than 98%. More skillfully, the arthroscopist can remove the proliferated synovial membrane and bone spurs, and repair the damaged meniscus and cruciate ligaments through the microscopic surgery, which is extremely effective and has few complications and sequelae. The vast majority of patients can walk on the ground the day after surgery. Generally, patients can be discharged from the hospital on the 2nd day after surgery depending on their recovery. Wounds heal on their own 7 days after surgery. Currently, 2 to 3 million patients undergo arthroscopic surgery in the United States each year, with a success rate of over 95%. President Clinton underwent arthroscopic reconstruction of the anterior cruciate ligament, and minimally invasive arthroscopic surgery has become the preferred method for the diagnosis and treatment of joint diseases. Prof. Zhiwei Wang is the Deputy Director of Department of Joint and Orthopedic Surgery of Changhai Hospital, and the leader of Bone and Soft Tissue Tumor Department of Changhai Hospital. He has been engaged in clinical diagnosis and treatment and research of joint surgery for more than 20 years, specializing in orthopedic surgery for all kinds of complex joint deformities, and taking the lead in carrying out minimally invasive treatment of joint injuries and diseases with arthroscopic technology in China, with more than 300 arthroscopic surgeries per year, and accumulating a wealth of experience in carrying out arthroscopic surgery of the knee and obtaining satisfactory clinical efficacy.