Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concern.. As per your complain pain at the back of knee can occur due to causes like Hamstring injury, Baker s cyst, posterior meniscus tear, arthritis, knee sprain etc.. I would suggest you to consult an Orthopedician and get evaluated and a thorough clinical evaluation and investigations like x Ray, MRI, CT SCAN and blood tests can help in making a confirmatory diagnosis so that an appropriate treatment can be instilled.. You can be advised to take Anti-inflammatory painkillers, muscle relaxant, cool/warm compress depending upon the problem, physiotherapy to strengthen the muscles and improve movement, while at times surgical correction might be required.. You should also avoid vigorous exercises, long hours of sitting or standing continuously and loose weight if obese.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.