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.

MRI of the knee showing partial ACL tear

MRI of the knee showing partial ACL tear

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.


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.


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.

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.

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