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Learn more about your ACL Procedure.

General Overview of Injury


The knee is composed of the femur (thigh), tibia (shin) and patella (knee cap). The knee is a hinge joint which allows flexion and extension but also allows some rotation with those motions. Between the femur and tibia are two cartilaginous discs called the medial meniscus and lateral meniscus. Together they are called menisci and deepen the knee joint which allows for more joint stability and shock absorption between the femur and tibia. There are four major ligaments in the knee and they are the anterior cruciate (ACL), posterior cruciate (PCL), medial collateral (MCL), and lateral collateral ligament (LCL). The ACL is located in the center of the knee along with the PCL. The ACL provides stability with rotational forces by preventing the tibia from translating anteriorly or forward.

Picture of Superior (top) view of right knee
Picture of front and back of knee
Picture of knee

Mechanism of Injury

The ACL usually is torn in two ways. The first is done with a shearing force of the tibia on the femur. This usually occurs when trying to slow down suddenly or with the athlete planting their foot and moving to change direction. The second is with a hyperextension injury where the ACL is stretched and tears. This usually occurs with stepping off a curb or being hit in the front of the knee.


An ACL tear is determined with an evaluation from a medical professional where they will test the integrity of the ligament. They will also use imaging such as x-rays and MRI to further confirm their diagnosis


The ACL provides stability to the knee. If it is torn then there is a decrease in the knee and the next stability provider is the medial meniscus. This is why there is a meniscus tear commonly seen when the ACL is torn. You may feel instances of giving way and weakness with the knee due to the instability. If you do not choose to have the ACL reconstructed then you will also allow more damage to occur to the menisci because they will take on more wear and tear from the shearing forces from your knee.


Surgery is not always required or wanted by a patient for an ACL tear. Rehabilitation can be done to help strengthen the surrounding muscle and avoiding activities that cause instability instances.

If surgery is required, Dr. Lowe will discuss the surgical process with you. Surgical reconstruction involves arthroscopic surgery to remove the torn ACL and reconstruct it with a new graft. Graft choices can be selected in two categories, which are an allograft or autograft. Allograft is a graft taken from a cadaveric donor. The second choice of graft is an autograft which means that it comes from the patient’s own body. Several graft choices can be selected as an autograft which include patellar tendon, quad tendon and hamstring grafts. Factors for graft choice include any health risks that would be listed on your completed patient history form, the patient's age, and what specific activities they will be returning to, i.e., sport, position, and participation level.

Graft Choices

There are several graft choices that can be chosen for the ACL reconstruction. There are two types of grafts which are allografts and autografts. Allografts are selected from cadaveric donors while autografts are taken from the patient’s own body.

Allograft Choices


The Achilles graft is taken from a cadaveric donor. Allografts allow for a faster return to daily living with no pain from a donor harvest site. The graft is selected and trimmed to fit the tunnels and fixated. The return to full athletic participation is usually 8-9 months post-operatively.

Autograft Choices

Patellar Tendon Graft

The patellar tendon graft is considered the gold standard for ACL reconstructions due to the graft having bone on both ends of the graft, which allows for great healing and fixation within the bone tunnels. The graft is usually taken from the surgical knee with the surgeon removing the middle third of the patellar tendon and suturing the remaining tendon together. The tendon is removed along with bony plugs from the patella and tibia. A disadvantage to this graft choice is that some patients complain of anterior knee pain or patellar tendon pain when returning to activity or kneeling. Return to full physical activity usually occurs around 6-7 months post-operatively.

Hamstring Graft

The hamstring graft is taken from the semitendinosus and gracilis muscles located on the medial side of the surgical leg. These grafts are harvested and then sewn together. This graft does not have any bony attachments(soft tissue graft) so when it is fixated into the tunnels, screws or buttons are used. The hamstring graft generally has less pain post surgically and return to daily activities quickly. The rehabilitation process is a little slower initially due to the inability to contract the hamstrings.

Quadriceps Tendon Graft

The quad tendon is taken from the surgical knee, and has a two soft tissue attachments from the patellar tendon. The graft is fixated in the femoral tunnel with a button and in the tibial tunnel it is fixated with a retroscrew and button. This is a great graft choice because it is a thicker graft, it doesn't cause a deficiency in HS and is less painful than patellar tendon.

Meniscus Injury

A meniscal tear likely accompanies an ACL tear when the injury occurs due to the meniscus being a secondary stabilizer of the knee. In order to repair a tear involving the meniscus there are two different techniques. There is a meniscectomy which will remove some of the damage cartilage and there is a meniscal repair. A meniscectomy allows for the damaged piece of meniscus to be trimmed out and the remaining meniscus to be smoothed out. This is usually done if the meniscus is torn in an area where there is not a lot of vascularization and a repair would not work well. A meniscal repair allows the surgeon to place sutures into the meniscus to allow it to heal together.

Dr. Lowe also performs meniscal transplant surgeries. Meniscal transplants are indicated when there is adequate loss of meniscal tissue either from an injury or previous surgeries as well as continued joint line pain. The meniscal transplant is from a cadaveric donor which has been matched to the specifications of the patient’s knee which can be determined from an MRI. To benefit from a meniscal transplant the patient needs to have good articular cartilage along the knee surfaces. Patients with moderate to severe arthritis are not good candidates for a meniscal transplant.

Revision ACL

It is the hope of Dr. Lowe and his staff that after you have an anterior cruciate ligament (ACL) reconstruction you lead a normal injury free life and return to all activities. The initial reconstruction is referred to as a primary ACL reconstruction. It is an unfortunate fact that sometimes even after you have your ACL reconstructed, that you can re-injure the ligament and require another reconstructive surgery. In most cases, if you re-injure your ACL graft, a revision reconstruction is needed. There are two general ways to perform an ACL revision: a Single-Stage procedure or a Double-Stage procedure.

Depending upon the placement of your primary ACL reconstruction graft, Dr. Lowe may decide to either do a one-stage or two-stage revision reconstruction. He will obtain an MRI to determine if the position of the previous graft, tunnel placement, or graft fixations are in the proper place or if completing bone grafting to the tunnels would be a better.

Other factors that help Dr. Lowe determine which revision approach to follow is the type of fixation devices that were used with the primary reconstruction and the type of graft that was used.

Single Stage vs. Double Stage

The primary graft must be debrided and a decision concerning the removal of fixation devices will be made. A single-stage revision may or may not require removal of the original hardware in either the femoral or tibial tunnels. If the primary graft was placed in a more vertical position versus an anatomical position on the femur, then removal of hardware may not have to be done.

Dr. Lowe may ask to get a CT or MRI to look at the placement of the graft, hardware used and the tunnel placement. All of these things will help him determine if this can proceed as a single stage or if 2 stages are required.

If there are 2 stages that are needed then Dr. Lowe will perform the first surgery to remove any hardware and to bone graft the tunnels.

With the failed graft removed, the hardware removed if needed, Dr. Lowe can progress with reconstructing the ACL with a new graft.

Some single stage revisions require a more extensive length of healing and some modifications to the patient's post-operative care may be made as deemed necessary by Dr. Lowe. Usually these modifications include weight-bearing status and range of motion limitations.

The second stage of the double-stage ACL revision reconstruction is reconstructing the ACL with a new graft. This second phase is usually performed approximately three months after the first stage. This duration may be modified as deemed appropriately by Dr. Lowe.

Rehabilitation Process

ACL (Anterior Cructiate Ligament) Reconstruction

Please note that the rehabilitation protocols located on this page are to be used as a general guideline in the overall treatment and plan of care for Dr. Lowe's patients. Supervised treatment and care under Licensed Physical Therapists and Licensed Athletic Trainers is essential in progressing patients through each phase of the rehabiliation process. Dr. Lowe will determine the appropriate progression of the specific protocol for each patient through follow-up clinical appointments and regular documentation from Physical Therapists and Athletic Trainers.

Platelet Rich Plasma and Bone Marrow Aspiration

Platelet Rich Plasma (PRP) is an autologous blood plasma that has a platelet count that is above baseline in a small volume. The platelets hold concentrated growth factors that induce wound healing. PRP can be done in an office visit or in the operating room with blood being drawn from the arm in a sterile manner. The blood sample is placed into a centrifuge and spun for several minutes. Once completed the blood and platelets separate and the platelets can be pulled into vial and are ready to be injected into the injured area.

Other Patient Handouts

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  • Picture of  The Anterior Cruciate Ligament Study Group (ACL)
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