Generic name of Viagra is sildenafil citrate tablets, and muscle soreness in limbs is one of its adverse reactions, which may also be due to excessive exertion in sexual activities or other reasons. Sildenafil citrate is mainly used for the treatment of erectile dysfunction, and its common adverse reactions include headache, myalgia, back pain, visual abnormalities, flushing, nausea, dyspepsia, etc. Therefore, hind leg soreness after using the drug may be due to its adverse reactions, and it will disappear on its own in 1~2 days. In addition, it is contraindicated for those who are allergic to the product and those who use nitrate drugs. In addition to the adverse effects of the drug, soreness in the back legs may be caused by excessive leg exertion during sexual activity, resulting in a buildup of lactic acid in the muscles. It may also be due to infection or other causes. It is recommended to rest for a few days and reduce the activity of the legs. If the leg pain is not relieved after 1-3 days, go to the hospital to find out the cause and take appropriate treatment.