30 years old knee weakness may be related to physiological factors such as strenuous exercise, and may also be related to rheumatoid arthritis, patellar chondromalacia, hypokalemia and other pathologic factors, according to the condition of the medication, physical therapy, surgical treatment and other methods of treatment. 1. Physiological factors: due to strenuous exercise or excessive labor and other factors, it can lead to excessive metabolic products in the body, lactic acid accumulation, causing generalized muscle pain, aching and weakness symptoms, no special treatment is needed, and it can be gradually relieved after sufficient rest. 2. Rheumatoid arthritis: rheumatoid arthritis belongs to the allergic reaction disease, can cause knee pain and weakness, can follow the doctor’s instructions to use non-steroidal drugs such as ibuprofen, meloxicam, etc., as well as anti-rheumatic drugs, to alleviate the clinical symptoms, and in severe cases, can be selected for surgical treatment. 3. Chondromalacia patella: Chondromalacia patella can cause knee pain and weakness, can be given glucosamine sulfate and other drugs to nourish the cartilage, but also can choose sodium vitrate for injection into the joint cavity, and when the condition is serious, need to carry out surgical treatment such as patellectomy. 4. Hypokalemia: due to vomiting, diarrhea and other factors can lead to low potassium, causing generalized weakness, should strengthen the diet and nutrition, can follow the doctor’s instructions to use potassium chloride slow-release tablets and other drugs. 30 years old knee weakness may also be caused by other factors, such as symptoms continue not to relieve, it is recommended that patients go to the hospital in a timely manner, improve the relevant laboratory tests, timely targeted treatment. All of the above drugs should be applied under the guidance of a physician, and should not be used without authorization.