Anterior Cruciate Ligament (ACL) Reconstruction – The Anterior Cruciate Ligament (ACL) is one of four stabilising ligaments of the knee. ACL  prevents abnormal anterior displacement and rotation of the lower leg. The ACL may be injured with excessive pivoting or twisting of the knee as well as hyperextension, hyperflexion or lateral trauma to the knee. When the ACL is torn, the patient may hear or feel a “pop” in the knee, followed by swelling and difficulty continuing their activity. The patient may have a hard time walking and may also feel a sense of instability. An ACL tear is best diagnosed in a physical examination by an orthopaedic physician. An MRI (magnetic resonance image) may be obtained to confirm an ACL tear, as well as identify injury to other parts of the knee.