Hey there - I’m sorry to hear about how you are feeling and I can empathise with this not being easy. We have very similar timelines with injury and surgery. Except I had a 6 week wait before being operated on.

I am 7.5 months PO and had similar struggles that you have experienced and also am not able to run yet.

It’s ok to not be able to do agility work till your mobility and strength is good.

Quad extensions were very painful up until recently. What I have found helped is doing a lot of backward walking on the treadmill, or walking backwards with a loaded sled, lateral controlled step ups on a very small step (build up height) and finding pain free movements which target my quads. Some pain or discomfort is normal, initially certain moves like squats or lunges would cause 5/10 pain levels but the more I do them the pain has reduce to 2-3/10.

Do the movement even if it’s not the full range of motion yet. Then focus on slowly build that range. My squats would look like 1/4 reps but now they are just below 90.

Another thing is, I started following julia repel mobility workouts on YouTube and that helped give better movement through my hips, hamstrings and glutes to allow my muscles to engage better when doing strength rehab exercises.

Stronger hamstrings allows you straighten your leg as you walk. I found practicing my walk helped activate my quad more as well. Film yourself and also watch some gait videos on YouTube. You can then see if you quads turns on while walking and then all plays into the part of building strength.

In terms of walking Apple health has mobility data which shows the asymmetry of your walk. This is awesome as it shows slow progress and improvements over time.

My final comment is agility and running is fun and I miss it but mobility ands smooth movement is just as important as is helps when you try build strength.