The weakness of the legs after intercourse is mostly considered to be a physiological phenomenon, but may also be due to electrolyte disorders, osteoarthritis and other conditions. 1. Physiological phenomenon: usually sexual life will consume a lot of physical strength, resulting in the accumulation of lactic acid in the leg muscles, which will appear the symptoms of leg weakness. And men in the ejaculation of the whole body muscles will be in a tense state, after ejaculation, the muscles will be relaxed, can also be manifested as leg weakness, generally belong to the normal physiological phenomenon. Most of them can recover on their own after proper rest. 2. Electrolyte disorders: such as sodium metabolism disorders may appear hyponatremia, hypernatremia, potassium metabolism disorders will appear hypokalemia, hyperkalemia. Calcium, magnesium and other metabolic disorders may occur. Patients often have nausea, vomiting, fatigue, dizziness and other symptoms, which can also appear after coitus, leg weakness phenomenon. 3. Osteoarthritis: the cause and pathogenesis of the disease is not clear, and is considered to be related to obesity, inflammation, heredity, trauma and other factors. Patients often appear in the cold, exertion joint pain and swelling discomfort, and even induced joint pain, some patients can also be manifested as weakness after coitus. Some patients may also experience weakness after intercourse. Patients may also experience stiffness in the joints and restriction of movement. It is recommended that people who have weakness after intercourse should allocate the time for sex reasonably and pay more attention to their own dynamics, and if abnormalities occur, they should seek medical treatment in time.