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ACL Reconstruction – Frequently asked questions that debunk the myths of ACL surgery

Surgical Treatment

When should I have my ACL fixed? – Timing of ACL reconstruction

There is no single perfect time for ACL reconstruction, and therefore timing varies from patient to patient.  In general, patients should regain full ROM, reduce swelling, and have quadriceps control prior to surgery. Occasionally patients are involved in a preoperative therapy program and attainment of full ROM can take 2 weeks or longer. It has been suggested in research that full ROM prior to surgery can decrease postoperative rehabilitation time, and improve postoperative range of motion.  One recent European study demonstrated superior long-term outcomes for patients that underwent 5 weeks of “pre-habilitation” prior to surgery.   In general, the stronger a patient is entering surgery, the better and faster the recovery afterwards.

However, patients with associated meniscus tears or osteochondral injuries, for instance, could sustain further damage be delaying surgery.  In a worst-case scenario, a repairable injury (ie. Meniscus tear) could become irreparable with further damage, delay in diagnosis, or continued participation in sport.  Obtaining a high-quality MRI and a careful, individualized consultation with Dr. Rice will clarify the ideal timing for each patient.

ACL Reconstruction
Surgery for ACL injury is an ACL reconstruction using a tendon graft and is typically performed using arthroscopic methods. The surgeon makes small incisions so that a pencil shaped instrument with a camera and lighting system attached can penetrate inside the knee joint and see the inside structures. The inside of the knee can be seen on a TV screen and the surgeon will perform surgery through several small incision points around the knee.  The tendon graft will function as a new ACL ligament, connecting the femur and tibia bones to prevent anterior (forward) translation of the tibia on the femur, which is the main function of the native ACL.  Ultimately the surgery restores stability of the knee, allowing return to pivoting, shifting, jumping, and running activities.

Which ACL graft is best for me?  Choosing among patellar tendon (BTB), hamstring, quadriceps, and the autograft/allograft debate

Graft Options

There are three common types of graft harvest sites for autograft ACL reconstruction:

+ patellar tendon: this commonly includes the central third of the patellar tendon with bone blocks from the patella and tibia; perceived advantages of this graft include high strength, composition similar to the native ACL, and healing of bone to bone, which may be more reliable and robust.  BTB graft is often referred to as the “gold standard” of ACL reconstruction and has among the longest track record of success.  Some studies report BTB Is the preferred choice for 80% + of professional athletes.  Dr. Rice recommends this graft for most patients.
+ hamstring tendon: traditionally this includes harvest of the semitendinosis and gracilis tendons, although more recently techniques have been developed using only the semitendinosis in quadrupled form, if sufficient size and length exists.  Hamstring tendons offer ease of harvest and may offer less postoperative pain for the patient in the early recovery period; many studies show comparable strength and long-term durability compared to BTB graft.  Dr. Rice’s concerns with hamstring autograft include:

  • anecdotal observations of increased postoperative laxity or (hamstrings seem to “stretch” out over time)
  • native hamstrings function to dynamically control anterior tibial translation (theoretically ‘stealing’ an ally in ACL function, or “robbing Peter to pay Paul” in knee stability); sacrificing them to create a new ACL could harm the balance of the knee
  • some (admittedly, a minority) of studies indicate higher rates of rerupture and recurrent instability with hamstring tendon ACLs

While hamstring remains a viable option, and has been a popular option for many years, it tends to exist as a third option in Dr. Rice’s practice for autograft reconstruction.

+ quadriceps tendon: less commonly utilized than the other two grafts but gaining in popularity, quadriceps tendon comprises a thick, strong graft choice that may include a plug of patella bone or be comprised of only tendon tissue.  This option often typically provides a thicker graft than can be obtained by BTB or hamstring, and with less kneeling pain discomfort than BTB.  It lacks bone-to-bone healing at one or both ends, however, and lacks the voluminous research the other two aforementioned grafts have, and much shorter followup in research literature.  Quadriceps tendon graft is often the second choice for autograft ACL reconstruction in Dr. Rice’s practice.

It is important to discuss graft options with Dr. Rice to select the right graft for you.  While some orthopedic research indicates lower re-tear rates with patellar tendon, a majority of the highest quality research indicates no significant difference among the three graft options, and successful outcomes are possible with all graft choices.

Do I want an ACL graft from my own body?  What is the quality of a donor tendon for ACL surgery?  Which ACL graft option results in less pain?  Which ACL graft option will give me the best results?

Autograft versus Allograft Debate

In addition to harvest site, another difference in grafts to consider is autograft versus allograft. Allografts are harvested from cadaver donors while autografts are harvested from the patient undergoing ACL reconstruction. Each graft has advantages and disadvantages.  Most orthopedic research has demonstrated lower re-tear rates using autograft tissue, and this is generally recommended in young competitive athletes under age 25.  However, autograft requires additional incisions and may result in more early postoperative pain.  Patients may perceive slower progress decreasing pain and restoring range of motion in the early rehab phase, although autograft completes the ligamentization process more rapidly than allograft tissue, and ultimate return to sport activity is the same or perhaps a month or two faster with autograft.

Patients choosing allograft may benefit from less pain immediately after surgery, and may feel better sooner, but the incorporation of the graft into a new ACL may take longer than autograft, and long-term re-tear rates are higher in allograft tissue.  Additionally, although increasingly rare given modern testing and sterilization techniques, disease transmission of hepatitis and HIV remains possible, generally considered a 1: 1.6 million risk.

While individual needs and goals vary significantly among patients, in general, Dr. Rice recommends autograft ACL reconstruction for patients under 25 years old, and allograft is a reasonable option for patients over 40 years old.  Patients between 25 and 40yo represent a “gray” area of the decision\-making algorithm and individualized discussion is necessary to make the best choice.

What are the general steps of ACL reconstruction surgery?  How is ACL surgery performed?

Anterior cruciate ligament reconstruction is a surgical procedure to replace the torn ACL with part of the patellar tendon or hamstring tendon taken from the patient’s leg. The new ACL is harvested from the patellar tendon or hamstring tendon. The patellar tendon connects the bottom of the kneecap (patella) to the top of the shinbone (tibia). Hamstring is the muscle located on the back of your thigh. The procedure is performed under general anesthesia. Your surgeon will make two small incisions around your knee. An arthroscope, small video camera, is inserted through one incision to see the inside of the knee joint. Along with the arthroscope, a sterile solution is pumped into the knee to expand it and enable the surgeon to have a clear view of the inside of the joint. The torn ACL will be removed and the pathway for the new ACL is prepared.

For patellar tendon graft, your surgeon makes an incision over the patellar tendon and takes out the middle third of the patellar tendon, along with its attachment to the bone. The remaining portions of the patellar tendon on either side of the graft are sutured back after its removal and the incision is closed. For the hamstring tendon graft, a small incision is made over the hamstring tendon attachment to the tibia and the two tendons are stripped off the muscle and the graft is prepared.

The arthroscope is reinserted into the knee joint through one of the small incisions. Small holes are drilled into the upper and lower leg bones around the knee joint. These holes form tunnels in your bone to accept the new graft. The graft is then pulled through the predrilled holes in the tibia and femur. The new tendon is then fixed into the bone with screws, to hold it into place while the ligament heals into the bone. The wounds are then closed with sutures and dressed.

Long Term Expectations

ACL reconstruction surgery has a 90% success rate in terms of knee stability, patient satisfaction, and return to full activity, which comprise the primary goals of surgery.  ACL reconstruction should also theoretically protect the menisci from further injury and slow degenerative changes in the knee joint, although orthopedic research proving this effect is still lacking.

The re-rupture rate of a reconstructed ACL is very low, generally 2-5% at an average of 2 years after surgery.  Of equal or greater concern is the risk of subsequent ACL injury on the opposite leg, which increases substantially from 1 in 3,000 to 1 in 50.

Patients who opt out of ACL reconstructive surgery may experience further injury to the knee joint, particularly to the menisci.  ACL-deficient patents are at higher risk for later meniscectomy, 20% over the 5 years following ACL injury.  Also, 70% of ACL deficient patients have signs of osteoarthritis in the knee.


  • Generalized complications such as infection, neurovascular injury, and thromboembolic disease are extremely rare (0.2-0.5%).
  • Deep vein thrombosis is another low probability (.1%) complication.
  • Graft misplacement complications due to the graft not placed anatomically can lead to motion problems, impingement, and graft failure. Careful attention to detail during surgery must be observed to avoid these complications, and this is increasingly uncommon as surgical techniques and technology have improved
  • Other complications include knee stiffness (5-25% incidence), anterior knee pain (10-20%), Patellar tendonitis (20% in 1st year, then rare afterwards), Patella fracture (.3-1.8%).

ACL Injury in Children

Incidence: ACL injuries in patients younger than 14 years vary from 3% to 10%. However, sports are becoming increasingly more competitive at younger ages, thus ACL injury incidence is expected to increase among the younger population.

Treatment: Initially, an ACL injury in children is treated non-operatively, using a similar treatment plan as described above, especially in children with widely open growth centers. With patients who fail conservative, non-operative treatment operative treatment must be considered because recurrent episodes of pivoting cause cartilage and mensical damage, which can lead to early degenerative changes.

Special considerations must be made when deciding whether or not to move forth ACL reconstructive surgery in children. There is possibility of interrupting and/or arresting normal bone growth that can result in significant leg length differences or angular deformity. Physeal-sparing (avoiding growth plate trauma) ACL reconstruction can be performed for younger patients, and improvements and technology and surgical technique have opened this option to many patients previously ineligible for surgery.  Nonetheless there remain concerns these surgeries sacrifice accurate restoration of the ACL anatomy for the sake of protecting the growth plates.

New Developments in ACL Reconstruction

While ACL reconstructions have allowed patients to return to high level sports and prevent meniscus tears, the surgery still has room for improvement. Recent studies of patients that had ACL reconstructions 10 years prior still develop early osteoarthritis. There has been a lot of interest in ACL augmentation and double bundle ACL reconstruction. These are surgical techniques that are aimed to preserve or replace the normal ACL in a more anatomic fashion.

ACL Augmentation

With ACL augmentation surgery, the goal is to preserve as much of the original ACL as possible while providing additional support via synthetic high-strength suture material. When the ACL is torn, the two bundles in the ACL may have varying degree of injuries.  The attempt is to preserve the patient’s ACL so that it can heal together with the support of suture material, and by definition maintain the original anatomy of the ligament.  Concerns with this technique include the poor healing potential of the ACL, although more recent studies suggest it may have better healing capacity than previously believed.  Nonetheless this is considered an experimental procedure at this time and may hold promise in the future.

Double Bundle ACL Reconstruction

There are two bundles to the ACL, namely the AM (anteromedial) and PL (posterolateral) bundles. Historically, only one graft is used and the anatomical position of one bundle of the ACL is reconstructed. Two or double bundle ACL reconstructions are performed to reconstruct both bundles of the ACL. This operation technically is more demanding and may be indicated for selected patients such as highly competitive professional athletes.  Laboratory testing demonstrates biomechanical superiority of double bundle ACL reconstruction under some conditions, but the benefits have not been clearly observed in real patients undergoing double bundle reconstruction versus single-bundle reconstruction.  At this time both surgeries are considered acceptable alternatives and single-bundle reconstruction remains the procedure of choice for the vast majority of surgeries performed in the United States.