Another year older, or just the aniversary

Status quo. I walk around OK and I have 100% flexibility but I don't have full strength. Can't do any high impact exercises or activities and I'm pretty much resigned to the fact that I probably never will. At least there is no pain. With the weather getting better I will be hitting the gym more often so perhaps I'll see some improvement. Even if its subtle its something.
 
I'm sure if you start off with some light leg exercises, you'll increase your strength in no time!
I'd imagine that Leg Press, Leg Extensions, and Leg Curls will be very beneficial. Light weight, high reps! Week after week, you'll probably notice drastic improvements in your strength and endurance!

Make sure to use proper form, and if you notice any pain (the bad kind), stop immediately. Also, it's good to allow full recovery time between workouts, so I'd say not to workout the same muscles (quads, hams, etc) any more frequently than once every 5-7 days.
 
Thanks for the advice. I've done physical therapy twice over an 18 month period. I have significant strength in my hamstrings. I can leg press as much as I did when I was 21 years old (about 180 pounds). Leg curls are not a problem either. Knee extensions are the key problem. I can only work out with about 15 pounds on my left leg and its like agony. Its not just the knee - its the development of the left quadricep. The trainers have told me they have never seen anything like it. When I came back for therapy the second time they told me they couldn't figure out how I was able to even walk as well as I did.
 
Yikes.
At least you can still do leg press. Leg press essentially works the same muscles as leg extensions (plus more), and in my opinion is the most important leg workout.
I really hope everything gets better for you.