It depends what's wrong with the knees and why they hurt when you run.
Years post-injury, most knee pain whilst running is because "everyone knows not to run with knee pain" so the brain just create pain. In which case, the right treatment is to re-train the brain not to think that (and there are many things that can help with that - mostly by applying a nice placebo pack and then proving to the brain that it's previous opinion was wrong).
Or it might need some sports tape (which can help with the above). Or it might need some shock absorption such as running on soft but predictable surfaces (which can help with the above). Or it might need some shock absorption in terms of trainers and insoles (which can help with the above, but also build dependency). Or it might need an orthopaedic brace (which can help with the above, but also build dependency). Or it might need a relatively minor retraining of your running gait (which can help with the above). Or it might need a major re-working of your running technique (which can help with the above). Or it might be that the hip, or the ankle are actually the areas that need to be addressed, but it's coming out in the knee as the point of previous injury. It's highly unlikely, but it might even be that there's still some damage from the previous injury that needs to be worked through first.
Ultimately, the best thing to do (shy of seeing a professional) is to run barefoot on a soft, predictable surface (like a rugby pitch), and start off with jogging tiny distances (say 10m) to prove to the brain that it's not an absolute that running = pain, and that you're just haggling with it as to what level of challenge is fair to start feeling pain at. That might be distance, it might be speed, it might be introducing side-steps, it might be uneven/unpredictable surfaces, it might be harder surfaces, it might be drag-running, it might be...
Start pathetically small, prove the concept, and build from there.
FTR: I may never got remotely close to playing against the All Blacks - but I have treated one (and a Bok Prop).
Using variations on the theme of the advice above I've also got a patient from being medically discharged from the army, and told she'd never walk unaided, to ditching the stick and running half-marathons.