It a combination of one aleve 220mg, and 25mg of diphenhydramine, aka benadryl.
I've never really understood why these drugs were combined, unless you can't sleep because your knee is hurting you.
Buy a bottle of generic NSAID (ibuprofen or naproxen). Buy a bottle of antihistamine (diphenhydramine).
If your knee hurts, take the NSAID. If you are having allergies or need to go to sleep in the next few hours, take the antihistamine. If your knee hurts and you want to go to sleep. Take them both. My way is far cheaper, and you are only taking the drug you need at the time. If you really want to go to sleep without waiting, call your doctor and get a script for a benzodiazepene or ambien.