How does a prp injection help the knee?

Still being debated: You've heard of cutting edge stuff, right? Well, platelet-rich plasma is bleeding edge. Theory is nice: concentrate your own growth factors then inject them back in where they're needed & voila! Except studies haven't been able to demonstrate voila! Check out http://www.runnersworld.com/injury-treatment/platelet-rich-plasma-knee-osteoarthritis & http://www.medscape.com/viewarticle/803372

Anti- inflammatory: PRP has growth/ healing factors, is anti-inflammatory and stimulates stem cells (via HGF and others). My commercial/ research colleagues use it for this all the time. It works as well a steroid injection but has none of the downside. Steroid mortgages your health-you get fast relief but you "pay for it" with slowed healing. This isn't what you want. I use PRP it a lot, including for my own knee.

It depends: I've done a few thousand PRP injections for musculoskeletal problems, and for some knee problems--osteoarthritis and patellar tendinitis--it works well in certain patients. It helps by releasing growth factors in the platelets when platelets are exposed to Type IV collagen. Osteoarthritis--it increases joint fluid (that's good!) and decreases cartilage catabolism (that's bad!)