This article is designed to equip you with an insight in to how an ACL injury can occur, the benefit of exercise rehabilitation prior to surgery (if you choose it) and the rehabilitation process and timeframes after surgery.
The ACL is a ligament that contributes to connecting the femur (thighbone) to the tibia (shinbone). This ligament stabilises the femur on the tibia and prevents the tibia from sliding forwards and twisting during movements such as the following: jumping, decelerating, and pivoting with sudden changes in direction . An ACL injury can result from severe twisting of the knee, usually explained by rugby players as “one player got me at the lower leg and two others pushed me to the side with the foot still planted on the ground”. This can also occur upon landing with the knee buckling towards each other as a result of the weight of the landing, which can be noted in netball. Commonly reported symptoms can include a popping in the knee, followed by swelling, and possible knee giving way when trying to walk on the injured side. Clicking and locking may also be associated with the injury, if other structures are damaged within the knee. Following the injury, there may be joint stiffness, lack of mobility, reduced strength, pain and swelling. Figure  specifies the ACL ligament.
To achieve an optimal outcome for regaining the strength and mobility in the knee in a safe manner, the following phases are recommended:
Before the operation , ideally, we will be working towards restoring the movement you have available in the joint and working on the awareness of how your leg moves. We will also work out ways to keep the rest of the body in shape without additional discomfort to the knee, and this will continue as you progress. The exercises involved in this phase would be a combination of the ones in the first two phases. You may be encouraged to cycle for 15-30 min per day, walk and lightly swim.
During the first two weeks  after the operation you will be able to gradually put more weight through the affected side, while again work towards reducing the swelling, restore the movement and work on gaining strength.
From two weeks to three months  we will be building on the exercises from the first phase, and work on increasing the strength of the muscles around the knee and your balance. As you build more confidence with movement and strength you may be able to start using equipment in the gym environment, as some machines can help train single leg activity without the full load of your body weight. A special consideration here is to avoid using the leg/knee extension  machine as this can put excessive strain on the repaired ligament unless specifically directed to work in safe ranges by your physiotherapist. Precautions such as these make it important to seek a registered physiotherapist, who can ask to see your surgical notes and take you through the initial stages of the rehabilitation, whilst also taking onboard advice from your surgeon.
From three months to six months  you may be on your way to build up the ability to run, hop and jumping/landing practice. Everyone progresses at different rate and it is mostly down to performing your exercises regularly to build muscle, strength, power, co-ordination and agility.
Finally, from six months to one year , if sport is your passion, we will be looking into gradually incorporating training if you partake in sporting activities.
Each stage has its own functional targets that need to be met and the time you need to give your body to naturally heal. Should you find yourself requiring an ACL repair, our Habit Physiotherapists can assist you through every step to regaining and exceeding your pre-injury function.
Figure  Torborg L. (2016). Mayo Clinic Q and A : Some activities increase the risk of ACL injury. Retried from https://newsnetwork.mayoclinic.org/discussion/mayo-clinic-q-and-a-some-activities-increase-the-risk-of-acl-injury/
 Frobell, R., Copper, R., Morris, H., Hutchinson, M. (2017). Acute knee injuries. In P. Brukner & K. Khan (Eds), Clinical Sports Medicine. (5th ed., pp. 713-768). NSW, Australia; McGraw-Hill Education.
 Dr Mark Clatworthy. (n.d.). ACL Physio Protocol. Retrieved from http://www.markclatworthy.co.nz/information-sheets.html .