Anterior Cruciate Ligament


The anterior cruciate ligament is one of the major ligaments of the knee joint.  It is located in the middle of the knee along with another major ligament aka posterior cruciate ligament.

The anterior cruciate ligament starts in the lower end of the femur or the thigh bone and ends on the upper end of the tibia or the shin bone.  The anterior cruciate ligament helps stabilize the knee and prevents the sliding of the tibia under the femur.

Anterior cruciate along with the posterior cruciate ligament help provide rotational stability to the knee joint.  An anterior cruciate ligament injury can happen in a sports related event, from a motor vehicle accident or even in daily activity.

It happens due to forceful twisting or hyperextension injury to the knee joint.  The tear usually happens due to pivotal injury that is abrupt change in rotational direction of the knee with the foot fixed on the ground or with the rapid deceleration of the knee.

Examples of events leading to ACL injury may be sudden change of direction or cutting or sudden stopping, landing from a jump in an incorrect manner or direct contact or collision such as in a football tackle or a motor vehicle accident.

At the time of injury, a pop can be felt or heard and is usually associated with the feeling of giving away. Within a next couple of hours, the knee is usually swollen and painful and has a buckling sensation especially while twisting or pivoting movements.

An ACL injury may be associated with injuries to other structures of the knee like the meniscus on the medial collateral ligament and occasionally a bone bruise.

These additional injuries may have additional presentations in the form of tenderness on the inner side of the knee and inability to bear weight. Initial injury is treated with rest, ice, elevation and compression with bandage or ace wrap (RICE protocol).

The patients following acute injury to the knee with swelling should seek medical attention. The history and physical examination can be suggestive of diagnosis of ACL tear.  X-rays are performed to rule out any obvious bony injuries.

In patients with high index of suspicion for a ligamentous injury, an MRI scan is usually performed.  Diagnosis of an ACL injury or tear is usually by an MRI or on arthroscopic examination especially with patients in whom MRI is contraindicated.

ACL injury can be in the form of complete tear or rupture or an incomplete tear in which only a few fibers of the ACL are injured, and the remaining ligament is intact.

Treatment of ACL injury usually depends on the patient’s age, activity level, physical requirements, and lifestyle as well as the injury being complete or incomplete.

In patients with high grade injury or complete tear, in young patients with high activity level and demand and a physical examination showing laxity of the knee will usually require a surgical treatment option for return to optimal level or return to preinjury level of activity and lifestyle.

In older patients with low activity level or demand or in patients with high-grade arthritis or patients with low-grade partial tears, a conservative treatment plan can be followed with optimal results.  Patients who are treated conservatively or nonoperatively are usually treated in a knee brace along with physical rehabilitation.

Patients who are older and have advanced knee arthritis are usually treated as if for their arthritis appropriately conservative or operative, most common surgery being Joint replacement.

In younger patients with low-grade tear or partial tears, gradual ACL rehabilitation program is followed before they can return to preinjury level.  Rehabilitation may take 4 to 6 months or longer especially in athletes.

Patients who are planned to be treated operatively usually undergo either of the two surgical plans:

  • ACL repair
  • ACL reconstruction.


Anterior cruciate ligament repair has recently become a successful option for carefully selected patients.  Patients with pull off or avulsion of ACL from the lower end of the thigh bone or the femur are good candidates for ACL repair.

This surgery allows retention of the native ligament and hence its lining and blood supply which allows early healing and recovery.  The repair can be augmented with the use of artificial sutures and tapes to support the native ligament during the period of healing and allow early rehabilitation.

The surgery is performed arthroscopically through small incisions using arthroscope and arthroscopic instruments.  A final decision to do a repair versus reconstruction is usually taken at the time of the surgery itself, though preoperative MRI can be helpful in making a treatment plan.

The postoperative recovery from an ACL repair is similar to that of ACL reconstruction except that the recovery is faster, and rehabilitation is also quicker.  The risks and complications for ACL repair are essentially the same as for ACL reconstruction except that there is decreased morbidity from the graft harvest site as there is no graft harvest in the surgery.


ACL reconstruction is usually performed in patients with midsubstance ACL tear as these tears are not amenable repair.  The native ligament needs to be removed and replaced with substitute.  The surgery is usually performed arthroscopically through small incisions and appropriate substitute graft is used. Possible options of substitute graft include:

  • Quadriceps tendon graft
  • Patellar Bone tendon bone graft
  • Hamstring tendon graft
  • Cadaveric Allograft

The type of graft to be used depends on the patient’s level of activity and requirement, it being a primary or a revision surgery, patient’s characteristics as well as patient’s decision.

The hamstring graft, bone tendon bone graft or the quadriceps graft are usually harvested from the patient’s same knee or occasionally from the other knee in cases of revision surgery.

An allograft is a cadaveric tendon graft which has been stored aseptically and is prepared and used to substitute the anterior cruciate ligament. Other associated injuries like meniscal tear can be taken care of at the same time as the ACL repair/reconstruction.



If you suspect you’ve injured your ACL, it’s essential to see a doctor for a proper diagnosis. They will likely perform a physical examination of your knee and may order additional tests such as:

  1. MRI (Magnetic Resonance Imaging): This imaging test can provide detailed images of the structures inside your knee, helping the doctor assess the extent of the ACL injury.
  2. X-rays: While X-rays don’t show soft tissues like ligaments, they can help rule out other potential injuries such as fractures.



The patients are usually seen by the physician and appropriate preoperative investigations including advanced imaging, blood work and ECG and chest x-rays as needed are done.

The patients may also need clearance from their primary care physician and anesthesiologist before the surgery.  The patients are instructed to come to the hospital two hours in advance.  The patients are taken to the preoperative area where they are seen by the anesthesiologist and appropriate procedure performed before the patient is taken to the operating room.

A nerve block is usually performed in the pre-operative area. In the operating room the patient usually is given general anesthesia before being positioned for the surgery.


Following the repair or reconstruction surgery, the patients are usually provided a knee brace and crutches and discharged home the same day. Patients are advised to use ice and elevation to control the swelling and pain for the initial few days and refrain from strenuous activities. Ice should be used for 15-20 minutes as a time as frequently as possible.

The patients are asked to ambulate with crutches under supervision for the first 24 hours, due to nerve block on the same leg causing it to be numb and weak.  The nerve block helps during the surgery as well as after the surgery by controlling pain.

Patients are encouraged to take care activities of daily living from the next day. They are allowed weight bearing with knee brace and crutches. They are provided with pain medications in the postoperative unit as well as for home.

Patients are asked to take off their dressing in 72 hours.  They can shower and change their dressing to a dry dressing.  Patients are encouraged to take nutritious and healthy food and are asked to take over-the-counter laxatives in case of the constipation.

Patients are usually seen in the outpatient office in one week where adjustment of the brace is performed, and the wound is examined.  Patient is usually enrolled in the physical rehabilitation program following the reconstruction surgery and are followed in office regularly at 3 to 4-week interval.

A gradual recovery from ACL takes place over the span of 5 to 8 month or longer. Patients are encouraged to strengthen quadriceps to same strength as on to the other side before they start any professional games.


Physiotherapy is an important part of the treatment and recovery after ACL surgery. It is also important for patients being treated non-operatively. Motivation on the part of the patient is key to recovery from ACL injury.

Physical Therapy should be started as early as possible. Preoperative physiotherapy is also helpful to understand and prepare the knee for surgery. The initial aim of physical therapy is to regain range of motion, reduce swelling and achieve full weight bearing.

This is carried out under supervision of a physiotherapist and physician and includes sessions as well as home based physical therapy as instructed. Rehabilitation will involve proprioceptive exercises and muscle strengthening activities such as bike riding, swimming etc.

Cycling can begin at 2 months, jogging can generally begin at around 3 months. The graft is strong enough to allow sport at around 6 months however other factors come into play such as confidence, fitness and adequate fitness and training.

The rehabilitation and overall success of the procedure can be affected by other associated injuries to the knee such as injury to the meniscus, articular cartilage or other ligaments.


Preventing ACL Injuries

Prevention: While ACL injuries can happen suddenly and unexpectedly, there are steps you can take to reduce your risk, including:

  1. Warm-Up Properly: Always warm up before engaging in physical activity, especially sports. A proper warm-up prepares your muscles and joints for the demands of exercise, reducing the risk of injury.
  2. Use Proper Technique: Whether you’re running, jumping, or changing direction, using proper technique can help reduce the strain on your knees and lower the risk of injury.
  3. Strength Training: Incorporate strength training exercises into your workout routine to build strong muscles around your knees, providing added support and stability.
  4. Wear Protective Gear: If you participate in sports that carry a risk of ACL injury, such as soccer or basketball, wearing appropriate protective gear like knee braces or supportive footwear can help reduce your risk.
  5. Listen to Your Body: If you experience pain or discomfort during exercise, don’t ignore it. Stop and rest, and consult a healthcare professional if the pain persists.




Complications are not common but can occur. It is pertinent that patients understand prior to making the decision of have this operation so you can make an informed decision on the advantages and disadvantages of surgery. These can be:

Medical (Anesthetic) complications

Medical complications include those due to your general wellbeing and due to Anaesthesia given before and during the surgery. These include but not limited to:

Allergic reactions to medications, excessive blood loss requiring transfusion with its low risk of disease transmission, heart attack, stroke, kidney failure, pneumonia, bladder infections.

Complications from nerve blocks such as infection or nerve damage. Serious medical problems can lead to ongoing health concerns, prolonged hospitalization.

 Surgical Complications:

  • Infection
  • Deep vein thrombosis and its subsequent complications including pulmonary embolism and possible death
  • Excessive swelling & Bruising
  • Joint stiffness
  • Tingling and numbness
  • Graft failure
  • Damage to nerves or vessels
  • Hardware problems
  • Donor site problems
  • Residual pain
  • Reflex Sympathetic Dystrophy

Some of these conditions may require hospitalization, aspiration, injections or even surgery

Certain patient population is at a higher risk for complication which include but are not limited to:

  • Previous failed surgeries
  • Smoking
  • Seizures
  • Obstructive sleep apnea
  • Obesity
  • High blood pressure
  • Diabetes
  • Other medical conditions involving your heart, lungs or kidneys
  • Medications, such as aspirin, that can increase bleeding
  • History of heavy alcohol use
  • Drug allergies
  • History of adverse reactions to anesthesia


  • Suspected cardiac problem: severe chest pain or pressure, shortness of breath, tightness in chest, pain in left arm, jaw pain, dizziness or fainting, unexplained weakness or fatigue, rapid or irregular pulse, sweating, cool, clammy skin, and/or paleness
  • Suspected Stroke: trouble speaking, changes in vision, confusion or other change in mental status
  • Suspected venous thrombosis: swelling of the legs, ankles, or feet, discomfort, heaviness, pain, aching, throbbing, itching, or warmth in the legs, sudden shortness of breath, chest pain, coughing up blood, rapid or irregular heart rate
  • Suspected Sepsis: high grade fever, with shivers associated with fatigue, dizziness, racing heart, pale or discolored skin, sleepy, difficult to rouse, confused, short of breath
  • Heavy bleeding from the surgical site
  • Severe allergic reaction with trouble breathing, swelling, hives


  • temperature more than 101 degrees Fahrenheit
  • increased pain or tenderness near the incision
  • poor pain relief
  • signs of infection: increased swelling, redness, increased drainage, increased warmth, pus, foul smell, bleeding at the incision, incision coming apart
  • inability to feel or move fingers or toes
  • pale blue, white or abnormally cold fingers or toes
  • nausea (upset stomach) or vomiting (throwing up) that won’t stop
  • increased tiredness
  • a generally worse feeling than you had when you left the hospital
  • problems urinating, severe constipation or severe diarrhea
  • a concern about any other symptoms that seem unusual


ACL reconstruction is the time-tested procedure which has given consistently good results especially in younger and athletic population as well as in patients with high demand lifestyle.  ACL repair is a recent advancement and has shown promising results in appropriately selected patients.

ACL surgery along with postop rehabilitation can give good results and take the patient back to preinjury level in 6 to 12 weeks.  It does require high level of motivation on the part of the patient as well as skills on the part of the surgery along with a good physical therapy and rehabilitation team for an optimal recovery.

Patients who are not a good candidate for arthroscopic surgery can be treated conservatively in a knee brace along with physical rehabilitation with fair results.

Do you have more questions? 

What is your ACL, and what does it do?

Anterior Cruciate Ligament or the ACL is an important ligament inside the knee. It is present in the middle of the knee, and pairs with another ligament called posterior cruciate ligament, or PCL. Both ligaments help in stability of the knee joint, and prevent the knee from sliding on itself, hence preventing the feeling of buckling, giving way, or falling. In the absence of either one, or both the ligaments, the knee is unstable, and the patient will have difficulty walking, but especially with running, pivoting, and cutting.

What does it feel like to have a torn ACL?

Patients who have a torn ACL usually remember an injury in which they may have fallen or got hit on the knee, with or without hearing or feeling of a pop in the knee joint. These patients have sudden onset of pain associated with swelling. They also have limping because of pain. These patients also have instability and may have episodes of buckling or giving way.

Can an ACL tear heal without a surgery?

In case there is a complete ACL tear, the chances of healing without a surgery are remote. That nevertheless does not preclude conservative treatment as patients with low demands can be treated with physical therapy. If the patient has a partial tear of the ACL then, there is chance that the patient may get better just with physical therapy. If the patient does not got a stable knee even after physical therapy, then they may need ACL surgery.

Is ACL surgery serious?

ACL reconstruction, or repair surgery of the knee, is one of the major arthroscopic surgeries of the knee. It involves inspection of the joint, with repair, or reconstruction of the ACL along with treatment of any associated injury like meniscal tear. The surgery itself may take one and a half to two hours to complete. The rehabilitation process after the surgery is tedious, and involves constant supervision with a physical therapist, and a physician.

Is surgery required for a torn ACL?

If the ACL is torn completely, and the patient is in high demand of work, or recreation, then ACL surgery is preferable to give stability to the knee. If the patient is in low demand work, or has multiple comorbidities, then patients may be treated conservatively. Patients who do not undergo ACL surgery have higher chance of getting injury to other parts of the knee, like the meniscus, and the cartilage.

Can you still walk with a torn ACL?

After the ACL is torn, the knee becomes unstable, which is worsened by strenuous activities, like running, or pivoting, and cutting. Patients can still walk with a torn ACL, and may, or may not, require a brace to stabilize the knee.

How long does it take to recover from a partially torn ACL?

Patients with partially torn ACL are instructed to do all of this, and, have a rehabilitation program with a physical therapist. They may take up to eight to twelve weeks to recover. Some patients may take longer periods depending on the ACL torn. Few patients may even fail rehabilitation protocol, and may have to undergo a reconstruction of ACL, later.

Can you still walk with a torn ligament in your knee?

A torn ligament in the knee does causes instability. If only a single ligament is torn, patient is usually able to walk, though he may have some instability, and may need to use a brace, or crutches for support. If the patient has injury to multiple ligaments, or ligaments and meniscus, it may be difficult for the patient to walk without having a feeling of instability, or giving way, and may have episodes of falling.

Can a partial ACL tear heal on its own?

A partial ACL tear, depending on the amount of ligament involved may heal on its own, and patient may recover by use of physical therapy. If the patient has high grade partial ACL tear, then these patients may not recover completely, and depending on the requirement of the patient, may need to undergo surgical reconstruction of the ACL.

Can ACL be repaired?

ACL tears if present early after injury and if MRI show that they are reparable, then a trial for repair can be given to the ACL. The ligament is fixed back to the bone using some sutures and buttons to allow a natural healing process and keep the native ligament in its place. Repair leads to early recovery and owing to the retention of native ACL, gives better proprioception and hence early rehabilitation and recovery.

Is ACL repair better than reconstruction?

ACL repair, if possible, give better result than reconstruction because in ACL repair, the native ligament is kept as such and is fixed back to the bone to allow healing. In case of reconstruction, a ligament substitute is put in place, which not only takes a longer time to heal, but also takes time for ingrowth of nerves and vessels, which may also still be incomplete to give a result similar to an ACL repair.

How long before I can return to sporting activity after an ACL reconstruction?

After an ACL reconstruction, patients must be involved in a rehabilitation program with the physical therapy under direct supervision of the therapist and the treating physician. Patients must be in brace initially, which is gradually weaned off in four to eight weeks. Patient is put in rigorous physical therapy program and is also allowed to strengthen his muscles in the gym after about three months from surgery. Patients must strengthen their quadriceps as well as the hamstrings and must regain full range of motion and power before they can indulge in a sporting event. They are puts into sports rehab program. It could take six to twelve months before a professional sportsman can return to play.

How long does it take to recover from a torn ACL?

A torn ACL, when treated surgically, may take up to 6 to 12 months to recover completely and allow the patient to do unrestricted activities as before the injury. In patients who do not opt to operate may have a long rehabilitation process with suboptimal results, but if the results allow the patient to live a satisfactory life in their activities of daily living as well as work and recreation, then the result is found to be okay.

What are the risks of ACL surgery?

The risks of ACL reconstruction arthroscopically include Medical (Anesthetic) complications like but not limited to: Allergic reactions, excessive blood loss, heart attack, stroke, kidney failure, pneumonia, bladder infections. Complications from nerve blocks such as infection or nerve damage. Complications due to surgery itself include infection, DVT, excessive swelling & bruising, joint stiffness, tingling and numbness, graft failure, damage to nerves or vessels, hardware problems, donor site problems, residual pain, reflex sympathetic dystrophy etc. Some of these conditions may require hospitalization, aspiration, injections or even surgery.

How long do you have to keep your leg elevated after ACL surgery?

Patients are encouraged to keep their knee elevated most times for a few weeks after ACL surgery. This is to decrease the swelling as well as the pain in the knee. Once the patient’s pain has decreased and the swelling is no longer there, the patient can decrease the time of leg elevation. If the pain and swelling recur, then the patients are instructed to use ice as well as elevation and compression to decease the pain and swelling.

How long does it take to be able to walk again after ACL surgery?

Patients can walk within a day after the ACL surgery with a brace. They are also asked to use crutches for support. Patient will be using a brace for four to six weeks. They may use auxiliary crutches for support, if needed.

How long do you have to be on crutches after ACL surgery?

Patients, after ACL surgery, have a brace on the knee, and may use auxiliary crutches for comfort. They may discard the crutches once they are able to ambulate without discomfort.
Is ACL surgery serious?

ACL reconstruction, or repair surgery of the knee, is one of the major arthroscopic surgeries of the knee. It involves inspection of the joint, with repair, or reconstruction of the ACL along with treatment of any associated injury like meniscal tear. The surgery itself may take one and a half to two hours to complete. The rehabilitation process after the surgery is tedious, and involves constant supervision with a physical therapist, and a physician.

How long do you go to physical therapy after ACL surgery?

Patients usually must go for six to nine months of physical therapy after an ACL reconstruction, for it to recover completely, from ACL surgery, depending on the patient’s requirement. If the patient is a sportsman, they may have to go to a sports rehabilitation program so as to recover completely, to a pre injury status.

Can a stretched ACL heal?

A stretched ACL can be treated with a brace and physical therapy and may heal over time enough to provide a patient with a stable knee. If the patient does not heal completely with the brace, and physical therapy, and is still unstable enough to handle activities of daily living, or work, without limitation, then he may need to undergo ACL reconstruction surgery.

When can I take a shower after ACL surgery?

Patients are usually asked to remove their dressing after 72 hours of surgery, and can take a shower after that. Patient can dab the surgical area dry and put band aids over it.

Can an ACL reconstruction/repair fail?

An ACL reconstruction/repair can fail, due to multiple reasons, including wrong surgical technique, injury, fall, or twisting of the knee. ACL surgery may also fail in the presence of infection. In case of ACL repair, surgery may fail to heal the native ligament and a reconstruction may have to be done. These patients may need to undergo a revision of the ACL reconstruction, to get a stable knee.

Do torn ligaments heal themselves?

Torn ligaments of the knee, if in place, and of low grade (partial), can heal by themselves. The lateral collateral, as the medial collateral ligaments are essentially treated conservatively with brace and physical therapy. In case of high grade ligament tear, and if the patient is not getting better with physical therapy and brace, the patient may need a surgical repair, or reconstruction of the ligament, to obtain stability.

How ACL surgery is done?

ACL surgery is most commonly done arthroscopically, in which a camera and a light source are introduced to the knee joint through small incisions. Surgical instruments are inserted through different incision, and the ACL is examined. If the ACL is completely torn, and not repairable, then it is debrided, and cleaned.

The replacement substitute for the ACL is then harvested, either from the hamstring muscles, patellar tendon, or the quadriceps tendon, to replace the ACL. Bone tunnels are then made into lower end of femur, and upper end of tibia to pass the graft, and the graft is fixed using sutures, and either screws or buttons. Any concomitant pathology if found inside the knee is also taken care of.

How long are you out for the torn ACL?

The torn ACL is usually treated non-surgically and may take up to eight to twelve weeks to heal. A patient is usually treated with a brace, and physical therapy. Patient may be out of work, depending on the type of work, from two weeks to eight weeks. If the patient is in high demand job with a lot of manual work, then they may be out for a longer period.

How long does it take to recover from an ACL and meniscus surgery?

The recovery of a combined surgery is a little longer than that of an ACL surgery. There are s slightly higher chances of complications and stiffness owing to increased surgical time and work done inside the knee. The loss of partial meniscus in cases of partial meniscectomy also plays a role in long term recovery of the knee. In cases of meniscus repair, the rehabilitation is slowed due the time needed for the healing of the meniscus.

Can ligaments grow back together?

If the ligament is in it’s place, especially near the, it’s, bony end, then they may heal with the help of bracing and physical therapy. If the ligaments are torn in mid substance then it is difficult for them to heal, because the healing between the two ends of ligaments is not optimal. The ligaments usually do not grow back, but they heal with a fibrous tissue between them.

How do you prevent an ACL tear?

The ACL tear is essentially caused due to injury or fall or contact sports. If a person is involved in high risk activities like contact sports, then they are advised to have strong musculature, especially in the quadriceps and the hamstrings, as this support the knee, hence preventing an ACL tear. If the patient has undergone an ACL reconstruction, or repair, surgery then they are instructed to strengthen their quadriceps as well as hamstrings before they go back into field, to prevent repeat tear of the ACL.

What are the causes of a torn ACL?

An ACL is usually torn due to fall, or injury, especially involving twisting of the knee, or with an indirect force; someone hitting the knee. This usually happens in a contact sport accident, but this may also happen in injuries, like automobile accidents.

Can I do without my hamstrings?

Patients who undergo ACL reconstruction using their hamstring muscles can still walk and function well with their knee with rehabilitation because of other muscles substituting for those hamstring tendons as well as partial or complete regeneration of the tendons.

Should I wear a knee brace to support my knee rather than undergo major surgery for ACL reconstruction?

Surgery for ACL reconstruction is essentially an elective surgery in which the patient must discuss and understand the need for the surgery. If the patient is symptomatic enough to have inability of daily living, work and/or recreation, then it is advisable to undergo ACL reconstruction. Wearing a knee brace cannot substitute for a deficient ACL and patient will still will have restriction with regards to his activity. The knee brace may help in stabilizing the knee for certain movements, but the patients will still not be able to perform a higher level of function with that knee.

How can I tell if I have got a serious ACL injury?

Patients with ACL injury do remember incident in which they may have injured their knee. This is usually associated with, swelling of the knee, pain along with limping. If the patient presents late, they may have symptoms of instability in which they would have knee buckling or weakness because of deficiency of the ACL. A diagnosis of ACL injury is usually made by examination followed by an MRI of the knee.

Dr Vedant Vaksha

I am Vedant Vaksha, Fellowship trained Spine, Sports and Arthroscopic Surgeon at Complete Orthopedics. I take care of patients with ailments of the neck, back, shoulder, knee, elbow and ankle. I personally approve this content and have written most of it myself.

Please take a look at my profile page and don't hesitate to come in and talk.