The Anterior Cruciate Ligament (ACL) is an important knee stabilizer. The ACL is a ligament deep inside the knee joint, where it runs from the femur to the tibia. It functions by restraining anterior (forward) tibial translation and limits rotatory movements of the knee. Since the ACL is so important to knee stability, it is one of the most commonly injured ligaments in the body.
Most injuries to the ACL occur during a non-contact twisting collapse of the knee. ACL tears are common during sporting participation, but also happen during everyday activities and as on-the-job injuries. Typical mechanisms of injury are landing wrong, quick change in direction, rapid deceleration, and direct impacts. There are some risk factors for ACL tears including female sex, ligamentous laxity, family history, limb malalignment, poor landing mechanics, and a prior ACL surgery.
During the injury, many patients will feel a ‘pop’ in the knee along with a feeling of instability and pain. Afterwards weight bearing may be difficult or impossible, though some people will still be able to get around. The knee will typically swell dramatically within a day of injury, after which range of motion will decrease. Within a couple weeks of injury, the swelling decreases and the pain from the initial injury mostly resolves. The knee at this point will feel unstable and ‘give-way’, particularly when doing any impact or twisting maneuvers. In general, any time the knee swells dramatically after an injury, my recommendation is to seek professional care, as this could be an ACL tear (up to 70% in younger individuals).
: During the clinical evaluation, I will ask about the history of your injury along with associated risk factors, and your current symptoms. A comprehensive physical exam is also important. We will evaluate the stability of the knee, and assess for any other concurrent injuries. The Lachman maneuver (where the tibia is gently pulled forwards on the femur) is an import way we can feel if the ACL is loose. We will also evaluate a set of X-rays, to see if there are any fractures, assess the growth plates (in younger individuals), and make sure there are no alignment issues. Finally, it is important to have an MRI done, which will show us the extent of injury within the knee.
It is common for other structures to sustain damage in conjunction with an ACL tear. Meniscus tears occur over 50% of the time. Damage to other ligaments (MCL, LCL, PCL) and the cartilage are also common. A thorough physical exam and a quality MRI scan will help find these other conditions.
Depending on your activity level and other associated injuries, you may choose either operative or non-operative treatment of your ACL tear. Those patients who choose to avoid a surgery may still engage in some sporting activities, but may experience signs of instability and giving-way that will limit certain activities. Most patients with a complete ACL tear oftentimes will decide on surgical treatment.
The role of physical therapy in the treatment of ACL tears is to reestablish dynamic stability within the knee, to decrease inflammation, and to increase strength. Oftentimes movement patterns and sports specific training are also a focus. Whether choosing surgical treatment or non-operative care, physical therapy will likely be a part of your recovery. For patients with an ACL tear who go on to decide on surgical treatment, I still recommend a short course of physical therapy to prepare the knee for surgery. The stronger your leg is going into surgery, the faster and easier the recovery will be.
Many individuals who sustain an ACL tear will go on to have a surgery to treat their condition. The most commonly recommended surgery is an ACL reconstruction. This is done arthroscopically (through small minimally invasive incisions), where I make a new ACL in the knee. In order to reconstruct the ACL, a graft is taken either from your knee (autograft) or from a cadaver (allograft). For younger patients and those with more vigorous activity demands we recommend using an autograft. The graft is placed into your knee through tunnels in the femur and tibia. The surgery takes about 90 minutes and you go home the same day. Weight bearing after surgery depends on other procedures performed (such as meniscus repair), and is patient specific. Generally, for an isolated ACL reconstruction, the patient may bear weight on their knee after surgery, but use crutches and a knee brace for protection.
Graft Choice: The two broad categories of graft choices are autograft (tissue taken from your own knee) and allograft (cadaver tissue). Autograft choices are quadriceps tendon (tendon above kneecap), hamstrings tendon, and patella tendon (tendon below kneecap). Each autograft option has its own particular pros and cons, and therefore I believe this is a very patient-specific decision. With the correct surgical techniques and rehabilitation, the end results is often no different between the different graft choices. My most commonly used autograft is currently the quadriceps tendon, as I have found it to have excellent clinical results and minimizes some of the cons of other grafts.
Return to Activity: Return to full sporting participation can take some time after surgery. The current recommendation is that patients wait to return to twisting/cutting/pivoting sports for at least 9 months. This allows the ACL graft to mature and strengthen inside the knee, and for your muscular strength and endurance to improve. Patients will go through different phases in their rehab. The first goal is to minimize inflammation, promote healing, and regain mobility within the first month. We then have you regain strength and neuromuscular control of the knee. We then begin to incorporate running and impact around the 3-4 month mark. Finally, you will progress towards sports specific training and return to play between 6-12 months after surgery.
Dr. Daniel Elkin is a leading Orthopedic Surgeon performing ACL Surgery in the Willamette Valley. He specializes in complex knee reconstruction and knee arthroscopy and is conveniently located in Salem, Oregon.