Brief Answer: most common cause is arthritis Detailed Answer: HI, thanks for using healthcare magic Joint pain that is worse on ambulation or standing is usually related to disorders of the bones or tendons which obviously bear more pressure or experience more trauma on standing or walking. In some cases a bursa can become inflamed and this can cause pain. There is a bursa (sac filled with fluid) at the back of the knee that can become inflamed. This however, would cause a tightness in the knee and pain that is worse both on standing and bending the knee back. Tendon injury would normally occur after a history of trauma to the area involved. In the absence of such injury, the pain is more likely related to the bones. The most common bone cause is arthritis. If you can feel the bones rubbing together when you place the palm of your hand over your knee and bend it then this the likely cause. There are different types of arthritis but osteoarthritis is most common. The treatment for most of the above conditions does not actually differ. It involves the use of anti inflammatory pain killers such as aspirin, ibuprofen, cataflam. The treatment is essentially the same because they are all associated with inflammation and this medication would reduce the inflammation. They should be used on a full stomach and should be available over the counter. The anti inflammatory effect would also reduce the swelling. If you can obtain a knee brace from your local pharmacy , it would also help. If there is no relief after 3 to 5 days of medication use or worsening , you should be assessed by your doctor. I hope this helps you, feel free to ask any additional questions

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