Is It Still Possible to Remove the Scars on my Knees for over Ten Years?

I have found that old white scars are difficult to treat and improve only slightly with intervention. That being said, the fractional co2 laser can be useful in some cases. 

Improving the Appearance of Old, Smooth, Light Color Scars may be achieved using certain laser devices. Fractionated laser devices may help stimulate new collagen in the area and, after multiple treatments, may improve its appearance and make it look closer in appearance to the surrounding normal skin. Examples of such lasers are the Fraxel ReStore and the Icon XD. 

Scars can be treated with lasers and some injections if they are still new and pink. Creams and gels won't help - don't waste your money. Once scars become older and white, the only thing you can do to remove them is to have them surgically excised and have the site re-closed properly. Then properly treat that site to minimize any scarring and discoloration.