A knee that has been sore for years is usually not a knee that has worn out. The ligaments around it have loosened, so the joint shifts a fraction with every step and snaps back. Bone and cartilage have no nerves and cannot feel that. The lining around the joint can, and it is the one that swells.
Stop the shifting and the pinching stops with it. Surgeons already brace a knee still after a repair for exactly this reason - the problem is that a hospital brace is something you cannot drive, work or get through a day in.
Revora™ DialLock is engineered in Germany to do the same job in something you wear under jeans. A dial on the side pulls internal laces across the joint, steel splints sit down both sides, and a gel ring takes the pressure off the kneecap. You still walk, bend and take the stairs.