opinions on my leg routine

looking for a little adicie if this is OK,I have suffered with pains in my knee for sometime so I didnt really train legs,I did martiall arts for a few years but since packing up this year and training my legs light plus a couple of courses of test and decca my knee feel 100 % better to the point I have started to go heavy (well to me its heavy)
here is my routine I have been doing for a few weeks and i have gone up in weight quite a bit in a short time.
warm up leg extensions on 1 plate for 10 reps then staright onto leg curl again 1 plate for 10 reps,I do this for 3 sets increasing the weight by 1 plate and up the reps to 15 then 25
I then start with 3 sets of 12 reps leg extensions again upping the weight so to fail on the last rep
then using the same reps and sets do leg curl
after a few stretches I then do squats on the smiths machine,tonight I managed my best weight yet of 3 sets of 12 for the last set of 12 using 2 plates aside,nice deep
then after a stretch hit the leg press for 3 sets of 12 again upping the wieght every set I managed again of 225Kilos for the last set of 12
last off standing calf raises again 3 sets increasing ever time and finish of with a fourth drop set to fail
as I said not massive weights but I have had knee problems over the years and since doing this my legs have improved,by the way Iam knocking on 45 years young
so does this look ok to do for a month or so and then change it around,to be honest Iam really enjoying the leg sessions

Hi m8 routine looks ok , and as you said you making progress and importantly you enjoying it so no need to change . 
When you get bored or progress stops then change a few things round .

Well said Bolt, keep at it while it's working and you are enjoying it.

Any exercise is better than none but need to use a BB for the squats, you will be isolating your quads with the smiths and putting your body in a unnatural plain of movement, BB squats you will be using your hips and stabilizers to lift and will make greater progress as this is a natural way of trying to lift a heavy weight and your body will respond better. Leg extentioms and curls are a good warm up exercises to get the blood flowing and stiff legged deads for hams. But carry on doing what you are doing if you are enjoying yourself and are making progress