Severed my quadricep tendon, completely off the kneecap, in April, '04, at age 50. Surgery and four months in a heel-to-crotch Bledsoe brace. Then, six months of P/T. From there, on my own, I ran steps and hills and lifted weights. I was able to hike, very carefully, on easy terrain about six months after the injury, but it took me a year and a half to get back to equal strength with my good quad. I'll never have the last 2 or 3 degrees of flexion and extension in the knee, but that presents no functional problems. After a year and a half, I considered myself fully recovered, and I've been hiking pain free since then.
What I took away from the whole miserable experience was (1) don't rush things, (2) follow your P.T.'s program religiously (p/t many days hurt worse than the original injury, and you'll be tempted to blow off a few sessions), and (3) continue to rehab on your own when p/t is done. And they aren't kidding when they say a positive mental attitude makes a huge difference.
And, you're young. See you out there soon.