Houston Orthopedic Surgeon for Knee Injury or Shoulder Injury

Anterior Cruciate Ligament FAQ

FAQ: ACL Tear

You have injured the anterior cruciate ligament in your knee. The following is a list of common questions and answers that I have compiled with the help of patients whom I’ve treated in the past. I know it’s sometimes difficult to ask questions of doctors or to remember to ask all the questions you had planned. I hope this will help you. If there’s anything else you’re wondering about, please feel free to ask and I’ll be glad to answer and probably add your question to this handout.

What is the ACL?

Why is it important?

Is anything else damaged inside my knee?

What would happen if I did nothing about this injury?

How is the ligament fixed?

Will I have to stay in the hospital?

Do the screws ever come out?

Does using the hamstrings or patella tendon weaken my knee?

Will I need a brace?

When can I walk on my leg after surgery?

Will I need rehab or physical therapy?

What do I have to do to get my knee ready for surgery?

When can I go back to work?

Risks of surgery (possible, but still uncommon)


What is the ACL?
There are two large ligaments inside your knee each about the size of your little finger that cross deep inside the joint. They are called the ACL (anterior cruciate ligament) and PCL (posterior cruciate ligament) and go from the femur (thigh bone) to the tibia (shin bone). They serve to stabilize the knee and allow it to glide through a smooth range of motion as you bend and straighten the leg. The ACL is the ligament in the front and the one most commonly injured. (Back to top)

Why is it important?
Without the ACL the knee is less stable. Without its stabilizing influence, the knee can buckle suddenly as it is used and this leads to cartilage damage and eventually to arthritis. This is usually not a problem for “straight-ahead” activities such as walking or jogging. However, it can be a big problem for activities involving twisting, pivoting, jumping, or suddenly changing direction. Examples of these activities include most sports (especially basketball, football, volleyball, soccer, skiing, etc.) and many jobs (such as carpentry, warehouse, refinery, etc.). (Back to top)

Is anything else damaged inside my knee?
About half the time when the ACL is torn there is also damage to the meniscus cartilage inside the knee. If present, this is something that can be taken care of at the same time ACL surgery is performed. You can usually tell whether there is a torn cartilage on examination but sometimes this is difficult. Occasionally, an MRI study can help but this is expensive and time consuming and usually is not necessary. (Back to top)

What would happen if I did nothing about this injury?
Usually within weeks of tearing the ligament, the pain and swelling go away and the knee starts to move well. The knee usually starts to feel nearly normal. The problem comes when you try to cut, pivot, or twist on the knee. Without the stabilizing influence of the ACL it will likely buckle and give way. Patients usually end up with a “trick knee” that gives way unexpectedly. The problem with this (beyond the embarrassment) is that with each episode of buckling, the joint gets scuffed and cartilage often tears leading to arthritis. So, engaging in jumping / cutting sports such as basketball, football, lacrosse, soccer, skiing, etc. frequently leads to the knee slipping out of joint.  Not only does this hurt, it also endangers the cartilage in the knee.  We reconstruct the ACL to stabilize the knee to allow twisting and cutting, and to protect the meniscus. Some people who elect to live less active lives (no jumping, cutting, pivoting, running sports) can get by without this ligament. But, if you seek to return to agility sports (basketball, football, volleyball, skiing, etc), surgery is the best option. If you saw the movie “Friday Night Lights” you will remember Boobie Miles, the star running back, hurting his knee and trying unsuccessfully to play with the tear. This was actually a fairly accurate representation of what happens. (Back to top)

How is the ligament fixed?
Older techniques consisted of sewing the torn ends of the ligament back together. This relatively simple operation didn’t work and the ligament almost always tore again. The standard operation is now reconstruction of the ligament where a tendon is used as a replacement for the anterior cruciate ligament.

There are three main choices for this substitute tendon. These are the central third of the patellar tendon (the tendon which runs from the knee cap to the shin bone), two of the hamstring tendons (the tendons behind the thigh), or a tendon from an organ donor. There are pros and cons to each. Keep in mind that whichever tendon is implanted, it will need time to mature and convert into living ACL ligament tissue. This takes about 6 months regardless of which tendon is used.

The patellar tendon has been used for years, provides a strong replacement for the ACL and can be securely fixed in place in the knee. However, use of this graft has a chance of side effects consisting primarily of pain/inflammation/tendonitis in the region of the patella and the patellar tendon. This is particularly a problem in those that need to kneel or crawl such as wrestlers, carpenters, etc. It is also slightly more painful in the acute post-operative phase than the other options. However, this graft is thought to be strongest and provide the tightest ligament in the long run. About 50% of my patients choose this graft, typically the younger more competitive athletes.

The hamstring tendons provide a graft that is just as strong, and the newer fixation methods are at least as strong as those for the patellar tendon. The two hamstring tendons sometimes re-grow; however, when they do not, the remaining three hamstrings get stronger to compensate for their loss. Most people do not notice any significant strength weakness after removal of these two hamstrings, but athletes in sports such as gymnastics, sprinting, wrestling/MMA, or ballet dancing may notice some weakness of knee flexion.  Also, those athletes that need to backpedal (such as defensive backs in football) need their hamstrings. The risks of complications and side effects are lower with usage of the hamstring graft with the patellar tendon graft, but this graft has a slightly higher chance of stretching out compared to the patellar tendon. About 20% of my patients choose this graft.

A third choice that is becoming more popular is use of the donor tendons (allograft). The main advantage of using the donor tendons is that there is less trauma to the patient’s leg because we do not have to remove any tendons to place them in the knee. Thus, there is less pain after the surgery and the early phases of the rehabilitation progress more quickly. Also, we can obtain as large a tendon as we need. When we take tendons from one area of the body to use in another, I am limited by how much the body has to spare. Essentially, we are “robbing Peter to pay Paul”. In small individuals with small tendons, there may not be enough to spare.

Over the last few years, approximately 30% of my patients have chosen to use the donor tendons (allograft) in order to minimize the trauma to their knee and accelerate their early return to daily activities. Note that using the allograft does not accelerate your return to sports, as the maturation process that every graft must undergo is actually slightly slower with the donor graft. There is some evidence that allografts may stretch out during this process. This is most common in adolescent and young adult patients. This graft is typically chosen by adults who are concerned about getting back to their normal daily activities at work and with their families.

There are some risks with the donor graft that the other grafts do not have. Specifically, it is theoretically possible that infection could be transmitted by the graft. The grafts are thoroughly tested, but it is theoretically possibly that HIV or hepatitis could be transmitted through the graft. A few cases of HIV transmission occurred in approximately 1990 and none have been reported since. At about that time, the testing methods improved significantly. The risks are less than those with blood transfusion and the most recent figures that I have seen indicate that the risk of HIV is less than 1 out of 2 million. Thus, while it is theoretically possible that HIV could be transmitted by the graft, it is extremely unlikely. I use a not-for-profit tissue bank with the best track record for graft quality and safety to minimize the risks and maximize the chances of a successful reconstruction. (Back to top)

The rehabilitation postoperatively is identical regardless of the graft chosen. There is less pain with the allograft compared to the hamstrings and less pain with the hamstrings compared to the patellar tendon. However, usually after a few weeks, this all equalizes. Each graft has an excellent track record and in truth the differences between them is quite small. Regardless of the graft that we choose, you have a 90% or better chance of getting back to all of your desired activities. (Back to top)

A recent advance has been the ability to use your own stem cells to augment healing of your ACL graft. I routinely do this for allografts and sometimes with the others. I can harvest your own stem cells from your bone marrow during the surgery and then apply them to your new ACL to accelerate healing. Though unproven, this is an exciting advance with great potential. 

Will I have to stay in the hospital?
Most patients go home on the day of surgery; however, if you desire, we can make arrangements for you to stay overnight. Everything is done arthroscopically (through small poke holes) except for harvesting the patellar tendon or hamstring graft which requires a short incision on the front of the knee. (Back to top)

Do the screws ever come out?
Almost never. They are actually inside the bone and rarely cause any discomfort. (Back to top)

Does using my own tendons weaken my knee?
If we use the two hamstrings, the remaining three compensate by getting stronger and there is some evidence that the two tendons re-grow so you won’t miss them. If I use the patellar tendon, the remaining portion is strong enough while scar tissue fills in the defect. (Back to top)

Will I need a brace?
This reconstruction is strong enough that you rarely need a brace for more than a few weeks to a month. There are a couple of exceptions. The most common is when the MCL (along the inner aspect of the leg) is torn at the same time. Patients need a brace for four to six weeks when the MCL and ACL are torn together. I often recommend a “sport brace” during the early phases of physical therapy, much like many football players wear on the field. (Back to top)

When can I walk on my leg after surgery?
You walk the same day as the surgery. You are given crutches but should put your weight on the leg right away. People frequently end up carrying the crutches by the end of the first week but I want my patients to use them until they can walk without a limp. (Back to top)

Will I need rehab or physical therapy?
Yes, this is very important. Your chance of achieving normal knee function after the surgery is greatly increased by the proper rehab. In fact, it takes a great commitment from the patient to get to the therapist and do the exercises with the appropriate diligence. It is also important to do only the correct exercises; as doing the wrong exercises can be more damaging than doing none at all. Unless otherwise instructed, you should start supervised physical therapy a few days after your surgery.

We want to minimize swelling for the first five days so you will focus on activating your quadriceps muscle with some simple exercises and keeping you knee elevated with some ice on it. This last through the first three-five days. After your first post-op visit PT will begin emphasizing gaining full range of motion and some strengthening exercises. As your motion improves, more emphasis is placed on strengthening. Usually within a week you are on a stationary bike and gradually progressed to a stair climber. You will also be doing some weight lifting exercises such as mini-squats and leg press.

I usually recommend therapy 3-5 times a week for the first 1-2 weeks and 3 times a week for 2-4 weeks and gradual transition to a home or gym-based program. Jogging is usually allowed at approximately 2-3 months if your motion and strength allow. There is a gradual return to sports with shooting baskets at 2-3 months, golf at 2-3 months, and so on. Full-speed sports are usually allowed at 5 months assuming your strength and agility have returned to near normal. (Back to top)

What do I have to do to get my knee ready for surgery?
The amount of swelling and stiffness you experience after surgery is related to the amount of swelling and stiffness you had before surgery. In other words, it is important to get rid of as much swelling and stiffness as you can before the operation. If the injury is old, your knee may bend well and have no swelling in which case you’re ready for surgery already. Usually when the injury is a new one, there is a lot of swelling and stiffness and you need “prehab” to prepare your knee for surgery. This consists of exercises and icing which enables your knee to be in the best possible shape (full motion and no swelling) for surgery. “Prehab” is also beneficial as it gives you a chance to familiarize yourself with some of the exercises you’ll be doing in the early postoperative period. (Back to top)

When can I go back to work?
This depends on what type of work you do. Usually deskwork can resume after three to five days. Jobs requiring significant amounts of walking can usually be returned to after two or four weeks when you feel comfortable off crutches. It’s usually a couple of weeks before you can drive safely. You can’t really climb or push/pull heavy loads for up to three months. Those jobs need to be avoided for awhile. Again, all of this is variable as everyone is different. (Back to top)

Risks of surgery (possible, but still uncommon)
The most frequent problem is stiffness. That is why I want your knee to be flexible beforehand, and why you need to use the CPM machine and attend physical therapy. I fully expect you to have your normal motion when your rehabilitation is complete.

Blood clots are also possible, but rare (less than 5%). You will have a stocking on your leg to minimize swelling and lower your chances of getting a blood clot in your leg. Keeping your leg mobile also decreases this risk. If you have additional risk factors (smoking, birth control pills, previous clots or phlebitis, etc.) then we will prescribe a blood thinner.

Infection also is rare, but possible (less than 1%). We sterilize your leg and use antibiotics to prevent this.

It is possible to stretch or re-tear the graft. For the first five months the graft is weak, so you will need to avoid twisting/cutting activities. Even after the graft is mature, you can still tear it. You tore the ligament God gave you so you can tear the one I give you too.

While any surgery should be taken seriously, please rest assured that complications are relatively rare. My practice is nearly entirely devoted to arthroscopic knee and shoulder surgery and I have done thousands of these reconstructions with an excellent success rate. I am confident that together we can create a knee that allows you to return to your desired activities. (Back to top)

Sample of Dr. Lintner’s publications regarding ACL tears. These and more are available on PUBMED website.

  1. Multistranded Hamstring Tendon Graft Fixation with a Central Four-Quadrant or a Standard Tibial Interference Screw for Anterior Cruciate Ligament Reconstruction. Starch DW, Alexander JW, Noble PC, Reddy S, Lintner DM. AM J SPTS MED, 31: 338-344, 2003
  2. The incidence and significance of femoral tunnel widening following quadruple hamstring ACL reconstruction using femoral cross pin fixation. Klein JP, Lintner DM, Downs D, Vavrenka K. ARTHROSCOPY, 19 (5), 470-476. 2003.
  3. The Effect of Strand Configuration on the tensile properties of quadrupled hamstring autografts. Rittmeister M, Noble P, Paravic V, Alexander J, Lintner DM. ARTHROSCOPY Volume 18 (2), 194-200, 2002
  4. Patellar tendon defect during the first year following ACL reconstruction: appearance on serial magnetic resonance imaging. Bernicker JP, Haddad JL, Lintner DM, Diliberti TC, Bocell JR. Arthroscopy, 14(8):804-809, 1998.
  5. One- and two incision ACL reconstruction: a biomechanical comparison including the effect of simulated closed chain exercise. Dalldorf PG, Alexander JS, Lintner DM. Arthroscopy, 14(2): 176-181, 1998.
  6. One versus two incision ACL reconstruction: A prospective, randomized study. Reat JF, Lintner DM. Am J Knee Surg, 10 (4): 198-208, 1997.
  7. Isometry measurements in the knee with the ACL intact, sectioned and reconstructed. Furia JP, Lintner DM, Saiz P, Noble PC. AmJ Spts Med 25(3):346-352, 1997.
  8. The radiographic evaluation of native ACL attachments and graft placement for ACL reconstruction: A cadaveric study. Lintner DM, Dewitt SA, Moseley JB. Am J Sports Med 24:1, 72-78, 1996.
  9. Increased tibial translation following partial sectioning of the anterior cruciate ligament; the posterolateral bundle. Hole RL, Lintner DM, Kamaric E, Moseley JB. Am J Sports Med 24:4, 556-560, 1996.
  10. Partial tears of the anterior cruciate ligament: are they clinically detectable? Lintner DM, Kamaric E, Moseley JB, Noble PC. Am J Sports Med, 23:1, 111-118, 1995.
  11. Athletic injuries: comparison by age, sport, and gender. DeHaven, KE and Lintner, DM. Am J Sports Med, 14(3):218-224, May/June, 1986.
  12. Comparison of multi-stranded hamstring graft fixation using four-quadrant tibial interference screw vs standard interference screw for ACL reconstruction. Starch DW, Alexander JW, Noble PC, Reddy S, Lintner D
Dr. David Lintner - Houston Orthopedic Surgeon