There are many studies about acupuncture as a remedy for all types of pain, including knee pain. One of these studies was actually a compilation of several clinical trials. It gathered information from all of them and reached a conclusion.
The authors reported that acupuncture could be useful to treat chronic knee pain. More clinical trials are required to make it a standardized treatment option, but we can use it as a safe remedy.
However, keep in mind that these studies take around 12 weeks. Thus, do not expect an immediate result, and give acupuncture time to work on you.