Chiropractic adjustment will help. Quadriceps exercise Hams Stretching- lie straight, take the leg up, pull the feet towards yourself, with a elastic tube or normal belt. repeat 10 times, twice a day. Sports Taping- stretch the tape from both ends and apply on the affected area Contrast Fomentation (Hot and Cold). Chiropractic physiotherapy.

Strength exercise of knee and first step  will take good legs

You have to continue with your knee strengthening exercises regularly. You should use your good leg first while climbing up the stairs. You should use your right leg (affected leg) first while climbing down the stairs.

If you are doing regular exercise than you don't need to worry about which leg you should place on stairs first. Since its 8 week its a phase of return to sports means you can do.

For this you need to visit in person at nearest available expert physiotherapist for proper assessment and rehab exercises.

It’s 8 weeks post operative case and you supposed to be run on treadmill and stairs climbing with both legs if you are not able to manage stairs in efficient way means some lacking in Physiotherapy exercises you need to focus on quadriceps and hamstrings muscle strengthening and joint proprioception

Agree with the previous comment. You should see a physiotherapist for proper rehabilitation.