Hi
ACL injury as you have experienced results in typical instability which is classically described as "giving way". This is particularly felt in turning at high speeds & while climbing down the steps.
In absence of ACL (when it is torn completely) hamstring muscles can be trained to perform restraining function of ACL thereby reducing instability in the knee particularly in activities like walking, climbing & squatting. The muscles are trained to contract where ACL function is expected. This is done by physiotherapist & is called proprioceptive training. Remember only increasing strength of muscles is not sufficient. you need to learn how to control the knee with the help of quadriceps & Hamstring muscles. This will help you minimizing instability & reduce possibility of chondral damage which is a long term effect of ACL tear. These exercises are also part of your postoperative rehabilitation. So learning them & doing them right from now will help you in postoperative rehabilitation phase.
it is a welknown fact that success of ACL reconstruction largely depends on effective postoperative rehabilitation. this is the time when you should get yourself introduced to various aspects of this phase.
You must also be conscious that you are nurturing an ACL deficient knee. Any indulgence in high speed contact sports will suubject it to further damage. So no footy till you undergo surgery & full course of rehabilitation. Patience in resuming sporting activities till your rehabilitation team gives you green signal is the best policy you can adopt now.
Best of luck for your upcoming surgery!!