Tearing your ACL is typically a traumatic event, most of my ACL patients report knowing they did something serious to their knee. This will usually land you in the office of an orthopedic specialist within a week of the incident. Once there is confirmation and diagnosis of an ACL tear it can often take up to 2 months to schedule a surgical date, it may be due to personal schedules, surgeon schedule, or researching graft choices. That being said, it is important to note that timing of the surgery can influence recovery. A recent Clinical Commentary by Evans et al, International Journal of Sports Physical Therapy 2014, reviewed relevant literature pertaining to time between injury and surgery. They discussed evidence to support that an 
ACL deficient knee becomes significantly more unstable, which increases risks for articular surface damage and additional ligament injury. Evans and colleagues also suggest that delaying surgery increases the risk for arthrofibrosis, or scar tissue build-up that can limit post-op knee ROM. However, the most important finding from their review may be that objective criteria including perioperative swelling, ROM and quad strength are the strongest indicators for when surgery should be performed. This evidence suggests that it is in your best interest to begin working on swelling reduction, ROM and leg strength prior to your surgical date.
* Update: Marina was kind enough to sign off to be my video model. At the time of filming she was 2 weeks post injury and just a few days post MRI confirmation of a left ACL tear. Below is a YouTube video with all of the exercises demonstrated with voiceover narration. All videos are contained in the rest of the blog with written explanations.
As long as you have clearance from your surgeon, here are some simple ideas to work on during your pre-op time at home or any gym without the need for much equipment.
Swelling control– Try to ice with something under your heel to help gain terminal knee extension. Several times per day, 20 min per session. Avoid sleeping with ice.
Stationary bike– Go for as much range of motion as possible. If you can’t make a full revolution, just work with what you have then reverse the motion backwards until you reach the end of your ROM then repeat and so on. Avoid raising your hip or turning your knee in just to get a full revolution. Once you can go around start extending your sessions and add some light resistance.
Patellar mobilization– The knee cap needs to be mobile in order to maintain knee motion, you do not want scar tissue to form between the patella and femur. Keep your leg as straight as possible and relax your quad. With your hands move your patella up & down and left & right for 1 min each.
Heel slides– Performed in supine (lying face up) long sitting (video) or seated in a chair, wear a sock on hardwood floor or tile so the foot can slide easily. The idea being to slide you heel back towards your hip as far as possible. Use your hamstrings to bend your knee as much as you can then use a strap to add some over pressure to gain range. Slide your heel forward to straighten the leg as much as you can to work on gaining full extension. Activate your quad and try to flatten the back of the knee against the floor or rolled up towel, if supine. If seated, slide your heel under you without altering your hip posture as far as you can, keeping your heel flat.
Hamstring, calf and quad flexibility– The hamstring and calf muscles both cross the knee joint so as they tighten up they will prevent full terminal knee extension. The quad will tighten up as your knee flexion ROM remains limited. Hamstring and calf stretching can be done in a long sitting position, flex at the hip, keep your back flat and stretch the hamstring, don’t worry about reaching your hands to your foot. For the calf you can use a towel or strap and pull the ball of the foot back, or stand in a stride stance with the involved leg in the back and the heel flat. Quad stretching can be done in prone (lying on your stomach), use a towel or strap and flex the knee until a stretch is felt in the quad. There may be some pressure in the knee, just go easy.
Gait training– Its common for people to adopt an abnormal gait pattern with an injured knee. Usually it is characterized by landing on the ball of the foot, taking a short opposite leg step, and a stiff involved leg swing. Work on landing on the heel, transition to foot flat then let the heel passively roll up. Don’t pick up the leg until you feel the ground under your big toe, then let the knee swing relaxed landing on the heel. Try to take even step lengths, even if they are small. The video below is my go-to for early gait training.
Basic leg exercises– These will not build strength, but will keep muscle contractility and help slow the atrophy prior to surgery. Straight leg raises (supine, side-lying and prone), knee extension/flexion, bridges, calf raises and toe raises.
Closed chain strength exercises– Closed chain exercises (feet on the ground) are safe and functional exercises to work on and can be done at a high level prior to surgery. Start simple with weight shifting in frontal and sagittal planes then progress to multiple planes and transverse rotational movements. Begin with unweighted box squats on a high box, progress to lower boxes, split stance and single leg exercises as you feel more comfortable. Avoid exercises that cause instability, high impact changes of direction, and absolutely NO reactive activities
Pre-op Physical Therapy– Depending on your insurance and your surgeon, you can do all of this and a whole lot more with a PT in a clinic, so ask your surgeon for a prescription and check your insurance coverage. Caution, you don’t want to exceed your yearly visits prior to surgery, this is a 6-9-12 month rehab process make sure of your PT coverage.
Ultimately you want to control swelling, maintain maximum range of motion and prevent atrophy so that you go into surgery as strong as possible. As long as there is no fracture, bucket handle or severe meniscus damage, or your surgeon does not advise PT, or has ordered you to be non weight bearing, there is no reason avoid these activities.
Chris Butler Sports PT 
Nice post, good information clearly explained
Thanks Annie.