It is mainly used for joint pain, so I would assume that it could do some good for his knee. My Mom had some problems (mainly the cartilage was wearing thin and was causing discomfort & pain) with her knees a few years ago and the Doc told her to get some Glucosamine and Chondrotin (usually you can get both drugs together in one pill) & also get some Gelatin tablets. She started taking those and within the next month, she was painfree. It doesn't work for everyone, but a lot of people swear by this stuff. It surely couldn't do any harm, unless you're allergic to it or etc. I do know that diabetics are not recommended to take this with out their Dr's ok (it will raise their blood sugars) & people who are allergic to shellfish are not to take this either.
I know there are several brands on the market and several different strengths with several different price ranges. Our most popular one at our Pharmacy is the Spring Valley brand Glucosamine & Chondrotin. I believe it is roughly $15 for 120 pills.??? Honestly, you can pay a boat load for a product like Osteo Bi Flex & get the same exact ingredients in a different brand for half the cost. You just need to read the ingredients and start comparing the labels.
OH btw, the Gelatin tablets help lubricate the joints and the other two help build the cartilage up in the joints. Another good thing about Gelatin, it makes your fingernails hard and make them grow quicker.
All three of these medications are natural medications too so that is a plus also!