Many middle-aged and elderly people often come to the clinic complaining of weakness in their knees, and most of them cannot tell whether the pain comes after the weakness or the pain comes after the weakness. What is this? Is it a calcium deficiency? Today we will help you solve this mystery. The so-called “weak leg”, also known as “leg weakness”, “knee weakness” is to describe a symptom that is normal walking or in the stairs, suddenly feel the knee joint can not eat strength, leg weakness Sometimes it can be accompanied by severe pain and a real fall. It is not the same as the kind of weakness that young people experience after strenuous exercise (e.g. long-distance running, soccer) with muscle aches and pains, which is an electrolyte disorder caused by excessive fluid loss without timely replenishment. The common causes include: 1, joint sports injury Meniscal injury is the most common type of injury, in the lower limb weight bearing, foot immobilization, knee joint slightly flexed, sudden excessive internal or external rotation knee extension (such as badminton, basketball, players in the attack and defense often occur), may cause meniscal tears. Meniscus injury will have obvious walking flat road hitting soft, sometimes there is joint pain, limited activity and popping sound when moving. Next is knee ligament injury. The stability of the knee joint is relatively poor when it is slightly flexed, so if it is suddenly subjected to external forces that cause valgus or inversion, it may cause medial and lateral collateral ligament and cruciate ligament injuries. This causes instability of the knee joint and the injured leg does not feel as strong as it used to be. It is obvious that the injured leg does not feel strong, the number of walking soft is more, the knee joint has the feeling of misalignment, and part of it will swell. 2, chronic joint disease When the fat pad is congested, hypertrophic and inflammatory due to trauma or long-term friction, and adhesions with the patellar ligament, fat pad strain will occur, thus limiting the knee joint activities. This condition occurs in people over the age of 30 who walk, hike or squat a lot. Patients may feel pain in the knee joint that is tender and worsens when fully extended, but joint movement is not restricted and symptoms are apparent after exertion. Chronic synovitis and abnormal hypertrophy of synovial folds in the knee joint due to trauma or overexertion can also cause “synovial impaction”, where the synovial membrane floating like water plants in the joint cavity is suddenly squeezed between the joints and a large amount of fluid is generated, causing the patient to feel weakness, pain, swelling, pressure and pain in the knee joint, and even interlocking symptoms This can affect normal activities. When these inflammatory factors stimulate the soft tissues around the knee, the muscles will suddenly spasm, leading to joint tenderness, and some active joints will have friction sounds. In severe cases, the knee may develop an inversion deformity and medial pain. There is also a cartilage lesion between the patella and femur that occurs in young people, known as “chondromalacia patellae”, which causes premature degeneration and loss of cartilage as the cartilage surface of the patella becomes uneven, sometimes accompanied by congenital patellar dislocation, resulting in symptoms of tenderness in the knee joint. If one or both sides of the knee are weak on a regular basis, it is necessary to go to the hospital for examination. After excluding the weakness of the knee due to cerebrovascular accidents, such as hemiplegia and loss of muscle strength, most of the problems are related to the bone and joint. It is expected that the cause will be clarified by physical examination, film, or even MRI. If the diagnosis is still unclear, there is now another reliable treatment technique – arthroscopy, because the lens of the arthroscope is very small and connected to the optical fiber. Under anesthesia alone, a very small incision can be made and the joint cavity can be inserted for observation, allowing direct visualization of the lesion, resulting in a 98% or higher diagnosis rate for intra-articular injuries. What’s more, the arthroscopist can remove synovial growths and bone spurs, and repair damaged menisci and cruciate ligaments, with excellent surgical results and few complications and sequelae. The vast majority of patients are able to walk on the ground the day after surgery. The patient is usually discharged from the hospital 3 to 5 days after surgery. The wound heals on its own 7 days after surgery. Currently, 2 to 3 million patients in the United States undergo arthroscopic surgery each year, with a success rate of over 95%. President Clinton underwent an arthroscopic ACL reconstruction, and today minimally invasive arthroscopic surgery is the preferred method of joint disease management.