A pilot study carried out in 2012 produced the following results in subjects that were on a waiting list for knee surgery:
"Myofascial trigger points were identified in all participants. Trigger point injections significantly reduced pain intensity and pain interference, and improved mobility. All participants had trigger points identified in medial muscles, most commonly in the head of the gastrocnemius muscle. An acute reduction in pain and improved functionality was observed immediately following intervention, and persisted over the eight-week course of the investigation."
[Trigger points are simply tight knots in the muscles. They can easily be self-treated using self massage. Anyone can do it]
"All patients had trigger points in the vastus and gastrocnemius muscles, and 92% of patients experienced significant pain relief with trigger point injections at the first visit, indicating that a significant proportion of the OA knee pain was myofascial in origin. Further investigation is warranted to determine the prevalence of myofascial pain and whether treatment delays or prevents TKA."
As far as I'm aware no further study has taken place. HOWEVER, given how easy it is to treat your own trigger points it'd be crazy not to give it a whirl and see if you can rid yourself of some or all of your pain!
Here's a little article that gives you some info on how to treat trigger points in your legs that tend to cause knee pain:
Bear in mind though that this article doesn't mention the gastrocnemius muscle - the research study found that to be a key player. You'll find that trigger point behind your knee, down an inch and on the outside edge. It's the big calf muscle running from behind your knee. You'll find diagrams online.
I hope this info helps someone to relieve or eliminate pain!