ACL Tear – Causes, Symptoms, Diagnosis, Treatment

ACL Tear/Anterior Cruciate Ligament Injury (ACL) is one of 2 cruciate ligaments which aids in stabilization of the knee joint. It is a strong band made of connective tissue and collagenous fibers that originate from the anteromedial aspect of the intercondylar region of the tibial plateau and extends posteromedially to attach to the lateral femoral condyle. The anteromedial bundle and posterolateral bundle form the 2 components of the ACL.   The ACL and the posterior cruciate ligament (PCL) together form a cross (or an “x”) within the knee and prevents excessive forward or backward motion of the tibia in relation to the femur during flexion and extension.

Anterior cruciate ligament injury is when the anterior cruciate ligament (ACL) is either stretched, partially torn, or completely torn. The most common injury is a complete tear. Symptoms include pain, a popping sound during injury, instability of the knee, and joint swelling. Swelling generally appears within a couple of hours.[rx] In approximately 50% of cases, other structures of the knee such as surrounding ligaments, cartilage, or meniscus are damaged.[rx]

Anterior Cruciate Ligament

Causes of Anterior Cruciate Ligament Injury

  • A sudden stop, twist, pivot or change in direction at the knee joint  – These knee movements are a routine part of football, basketball, soccer, rugby, gymnastics and skiing. For this reason, athletes who participate in these sports have an especially high risk of ACL tears.
  • Extreme hyperextension of the knee – Sometimes, during athletic jumps and landings, the knee straightens out more than it should and extends beyond its normal range of motion, causing an ACL tear. This type of ACL injury often occurs because of a missed dismount in gymnastics or an awkward landing in basketball.
  • Direct contact – The ACL may be injured during contact sports, usually during direct impact to the outside of the knee or lower leg. Examples are a sideways football tackle, a misdirected soccer kick that strikes the knee or a sliding tackle in soccer.

ACL tear Causes may include

  • Changing direction rapidly (also known as “cutting”)
  • Landing from a jump awkwardly
  • Coming to a sudden stop when running
  • Direct contact or collision to the knee (e.g. during a football tackle or a motor vehicle collision)
  • landing awkwardly from a jump
  • twisting movements, particularly when your foot is on the ground
  • quickly changing direction when running or walking
  • slowing down or stopping suddenly when running

These movements cause the tibia to shift away from the femur rapidly, placing strain on the knee joint and potentially leading to the rupture of the ACL. About 80% of ACL injuries occur without direct trauma. Risk factors include female anatomy, specific sports, poor conditioning, fatigue, and playing on a turf field.[rx]

Female predominance

Female athletes are two to eight times more likely to strain their ACL in sports that involve cutting and jumping as compared to men who play the same particular sports.[rx] NCAA data has found relative rates of injury per 1000 athlete exposures as follows:

  • Men’s basketball 0.07, women’s basketball 0.23
  • Men’s lacrosse 0.12, women’s lacrosse 0.17
  • Men’s football 0.09, women’s football 0.28

The highest rate of ACL injury in women occurred in gymnastics, with a rate of injury per 1000 athlete exposures of 0.33. Of the four sports with the highest ACL injury rates, three were women’s – gymnastics, basketball, and soccer.[rx]

Differences between males and females identified as potential causes are the active muscular protection of the knee joint, differences in leg/pelvis alignment, and relative ligament laxity caused by differences in hormonal activity from estrogen and relaxin.[rx][rx] Birth control pills appear to decrease the risk.[rx]

Dominance theories

Femur with Q angle – the angle formed by a line drawn from the anterior superior iliac spine through the center of the patella and a line drawn from the center of the patella to the center of the tibial tubercle

Some studies have suggested that there are four neuromuscular imbalances that predispose women to a higher incidence of ACL injury. Female athletes are more likely to jump and land with their knees relatively straight and collapsing in towards each other, while most of their body weight falls on a single foot and their upper body tilts to one side.[rx] Several theories have been described to further explain these imbalances. These include ligament dominance, quadriceps dominance, leg dominance, and trunk dominance theories.

Symptoms of Anterior Cruciate Ligament Injury

When an individual has an ACL injury, they are likely to hear a “pop” in their knee followed by pain and swelling. They may also experience instability in the knee once they resume walking and other activities, as the ligament can no longer stabilize the knee joint and keep the tibia from sliding forward.[rx].[rx]

  • Feeling a “pop” inside your knee when the ACL tears
  • Significant knee swelling and deformity within a few hours after injury
  • Severe knee pain that prevents you from continuing to participate in your sport (most common in partial tears of the ACL)
  • No knee pain, especially if the ACL has been completely torn and there is no tension across the injured ligament
  • A black and blue discoloration around the knee, due to bleeding from inside the knee joint
  • A feeling that your injured knee will buckle, “give out” or “give way” if you try to stand

Diagnosis of Anterior Cruciate Ligament Injury

Physical examination

Physical examination of the knee usually follows a relatively standard pattern.

  • The knee is examined for obvious swelling, bruising, and deformity.
  • Areas of tenderness and subtle evidence of knee joint fluid (effusion) are noted.
  • Most importantly, with knee injury ligamentous, stability is assessed. Since there are four ligaments at risk for injury, the examiner may try to test each to determine which one(s) is (are) potentially damaged. It is important to remember that a knee ligament injury might be an isolated structure damaged or there may be more than one ligament and other structures in the knee that are hurt.
  • In the acute situation, with a painful, swollen joint, the initial examination may be difficult because both the pain and the fluid limit the patient’s ability to cooperate and relax the leg. Spasm of the quadriceps and hamstring muscles often can make it difficult to assess ACL stability.
  • A variety of maneuvers can be used to test the stability and strength of the ACL. These include the Lachman test, the pivot-shift test, and the anterior drawer test. Guidelines from the American Academy of Pediatrics suggest the Lachman test is best for assessing ACL tears.
  • The Lachman test is performed as follows:
    • The damaged knee is flexed to 20-30 degrees.
    • The examiner grasps tibia and puts their thumb on the tibial tubercle (the bump of bone just below the knee where the patellar tendon attaches.
    • The examiners other hand grasps the thigh just above the knee.
    • The tibia is pulled forward and normally, there should be a firm stop if the ACL is intact. If the ligament is torn, the tibia will move forward and there will be no endpoint and it feels mushy.
  • The unaffected knee may be examined to be used as a comparison.

It may be difficult to examine some patients when muscle strength or spasm can hide an injured ACL because of the knee stabilization that they can provide.

Multiple maneuvers are employed to test the ACL and include the anterior drawer, the pivot shift, and the Lachman tests. These tests should be performed whenever there is suspicion for injury to the anterior cruciate ligament.

  • The anterior drawer test – is performed with the patient lying supine with their affected knee flexed to 90 degrees and the foot in a planted position (Sometimes it is easiest for the clinician to stabilize the patient’s foot by sitting on it). The clinician will grip the proximal tibia with both hands and pull with an anterior motion. If there is excessive anterior motion and instability, then the test is positive. It may also be useful to compare to the unaffected knee as patients may have increased laxity of the ACL that is not pathologic. This test has a sensitivity of 92% and specificity of 91% in chronic injuries, but not acute injuries.
  • The pivot shift test – is performed with the patient in the supine position. The clinician should hold the patient’s lower leg and begin with the knee in extension and flexion of the hip to 20 to 30 degrees. Next, the clinician will bring the tibia into the internal rotation with one hand and begin placing valgus stress on the knee using the other hand. While holding this position, the knee should now be flexed. This causes stress, instability, and ultimately subluxation of the ACL of the affected knee. With flexion of the knee, if the tibia subluxes posteriorly and one may feel a “clunk”; this would indicate a positive test. This test can be difficult to perform in patients who are guarding, and some may not allow the clinician to perform the test. This is a highly specific test (98%) when positive, but is insensitive (24%) due to the difficulty in evaluation secondary to patient pain and cooperation.
  • The Lachman test – is performed with the patient in the supine position with the knee flexed to about 30 degrees. The clinician should stabilize the distal femur with one hand and with the other hand pull the tibia toward themselves. If there is increased anterior translation, then this is a positive test. Again, comparing to the unaffected side may be helpful. This test has a sensitivity of 95% and specificity of 94% for ACL rupture.


  • Tests – Your doctor may ask you to lie on your back and bend your hips and/or your knees at certain angles. He’ll then place his hands on different parts of your leg and gently shift you around. If any of your bones move in a way that isn’t normal, that could be a sign that your ACL is damaged.
  • X-ray – Soft tissues like the ACL don’t appear on X-rays, but your doctor may want to rule out broken bones.
  • MRI or ultrasound – These exams can show both soft tissue and bone. If you have a damaged ACL, it should appear on the images.
  • Arthroscopy – This literally means to “look within the joint.” During the exam, an orthopedic surgeon makes a small cut in your skin. He inserts a pencil-sized tool that contains a lighting system and lens (arthroscope) into the joint. The camera projects an image of the joint onto a TV screen. Your doctor can see what type of injury you have and repair or correct it, if needed.

Stage  of Anterior Cruciate Ligament

An ACL injury can further classify as a grade I, II, or III sprains.

  • Grade I – The ligamental fibers are stretched, with a tear that is less than one-third of the ligament. Mild tenderness and swelling are present. The knee joint feels stable with a knee laxity < 5 mm.
  • Grade II – A partial tear (between one-third to two-thirds of the ligamental fibers) is present. Mild tenderness and swelling with some loss of function are present. The joint may feel unstable with increased anterior translation (a knee laxity of 5 to 10 mm). The patient feels pain, and the pain may become exacerbated with Lachman’s and anterior drawer stress tests.
  • Grade III – The fibers have completely torn. Tenderness and limited pain (relative to the seriousness of the injury) are features. The degree of swelling may be variable. The knee feels unstable, with rotational instability (positive pivot shift test). A knee laxity is greater than 10  mm. Haemarthrosis (bleeding into the knee joints) is observable within 1 to 2 hours.

An acute ACL rupture commonly occurs among sports players, especially those aged 14 to 19 years. The incidence of ACL injury is higher among female athletes due to the following reasons:

  • Smaller ACL and narrower intercondylar notch – Females who are non-athletes and aged 41 to 65 are predisposed to ACL injuries if they have narrow intercondylar notches.
  • Wider pelvis and greater Q angle – A wider pelvis increases the angle of the femur toward the central patella. The greater the Q angle, the greater pressure is applied to the medial aspect of the knee, which can lead to an ACL tear.
  • Lax ligaments – Female ligaments with more elastic muscle fibers tend to be laxer than male ligaments. Excessive joint movements with increased flexibility may contribute to the higher incidence of ACL injury among females.
  • Greater quadriceps to hamstring strength ratio – Females tend to have poor hamstring strength compared to men. The imbalance of strength between the hamstring and quadriceps muscles may increase the risk of ACL injury.

Treatment of Anterior Cruciate Ligament Injury

Non-Surgical Treatment Options

  • Patient education
  • Activity modification
  • Physical therapy
  • Weight loss
  • Knee bracing
  • Acetaminophen
  • Nonsteroidal anti-inflammatory drugs (NSAIDs)
  • COX-2 inhibitors
  • Glucosamine and chondroitin sulfate
  • Corticosteroid injections
  • Hyaluronic acid (HA)

The American Academy Of Orthopedic Surgeons (AAOS) Recommends This Treatment.

  • Weight loss – is valuable in all stages of ACL injury. It is indicated in patients with symptomatic ACL injury with a body mass index greater than 25. The best recommendation to achieve weight loss is with diet control and low-impact aerobic exercise.
  • Knee bracing – in the setting of ACL injury includes unloader-type braces that shift the load away from the involved knee compartment. This may be useful in the setting where either the lateral or medial compartment of the knee is involved such as in a valgus or varus deformity.
  • Immobilization – Your doctor may recommend that you wear a brace for 3 to 4 weeks. This stabilizes the knee while it heals.
  • Weightbearing –  Because putting weight on the knee may cause pain and slow the healing process, your doctor may recommend using crutches for the first week or two after the injury.
  • Physical therapy – Once the knee has started to heal, your doctor will recommend physical therapy to help your child regain normal motion. Specific exercises will strengthen the thigh muscles holding the knee joint in place. Your commitment to the exercise program is important for a successful recovery. Typically return to activity 3 to 6 weeks after the injury.
  • Emergent closed reduction followed by vascular assessment/consult – If indications to considered an orthopedic emergency, vascular consult indicated if pulses are absent or diminished following reduction if arterial injury confirmed by arterial duplex ultrasound or CT angiography
  • Immobilization as definitive management – successful closed reduction without vascular compromise, most cases require some form of surgical stabilization following reduction, outcomes of worse outcomes are seen with nonoperative management/prolonged immobilization will lead to loss of ROM with persistent instability.
  • Rest Your Leg – Once you’re discharged from the hospital in a legislating, your top priority is to rest your and not further inflame the injury. Of course, the arm sling not only provides support, but it also restricts movement, which is why you should keep it on even during sleep. Avoiding the temptation to move your will help the bone mend quicker and the pain fades away sooner.
    • Depending on what you do for a living and if the injury is to your dominant side, you may need to take a couple of weeks off work to recuperate.
    • Healing takes between four to six weeks in younger people and up to 12 weeks in the elderly, but it depends on the severity of the radial head fractures.
    • Athletes in good health are typically able to resume their sporting activities within two months of breaking they’re ulnar styloid depending on the severity of the break and the specific sport.
    • Sleeping on your back (with the sling on) is necessary to keep the pressure off your shoulder and prevent stressing the hip injury.

Eat Nutritiously During Your Recovery

  • All bones and tissues in the body need certain nutrients in order to heal properly and in a timely manner. Eating a nutritious and balanced diet that includes lots of minerals and vitamins are proven to help heal ACL injury of all types. Therefore focus on eating lots of fresh produce (fruits and veggies), whole grains, lean meats, and fish to give your body the building blocks needed to properly repair your. In addition, drink plenty of purified water, milk, and other dairy-based beverages to augment what you eat.
  • ACL injury need ample minerals (calcium, phosphorus, magnesium, boron) and protein to become strong and healthy again.
  • Excellent sources of minerals/protein include dairy products, tofu, beans, broccoli, nuts and seeds, sardines, and salmon.
  • Important vitamins that are needed for bone healing include vitamin C (needed to make collagen), vitamin D (crucial for mineral absorption), and vitamin K (binds calcium to bones and triggers collagen formation).
  • Conversely, don’t consume food or drink that is known to impair bone/tissue healing, such as alcoholic beverages, sodas, most fast food items and foods made with lots of refined sugars and preservatives.


  • Antibiotic – Cefuroxime or Azithromycin, or  Flucloxacillin or any others cephalosporin/quinolone antibiotic must be used to prevent infection or clotted blood remove to prevent furthers swelling and edema.
  • NSAIDs – Prescription-strength drugs that reduce both pain and inflammation. Pain medicines and anti-inflammatory drugs help to relieve pain and stiffness, allowing for increased mobility and exercise. There are many common over-the-counter medicines called non-steroidal anti-inflammatory drugs (NSAIDs). They include and KetorolacAceclofenacNaproxen, Etoricoxib.
  • Corticosteroids – Also known as oral steroids, these medications reduce inflammation.
  • Muscle Relaxants –  These medications provide relief from associated muscle spasms.
  • Neuropathic Agents – Drugs(pregabalin & gabapentin) that address neuropathic—or nerve-related—pain. This includes burning, numbness, and tingling.
  • Opioids – Also known as narcotics, these medications are intense pain relievers that should only be used under a doctor’s careful supervision.
  • Topical Medications – These prescription-strength creams, gels, ointments, patches, and sprays help relieve pain and inflammation through the skin.
  • Calcium & vitamin D3 – to improve bone health and healing fracture. As a general rule, men and women age 50 and older should consume 1,200 milligrams of calcium a day, and 600 international units of vitamin D a day.
  • Antidepressants – A drug that blocks pain messages from your brain and boosts the effects of endorphins (your body’s natural painkillers).
  • Glucosamine & DiacereinChondroitin sulfate – can be used to tightening the loose tension, cartilage, ligament, and cartilage, ligament regenerates cartilage or inhabits the further degeneration of cartilage, ligament. They are structural components of articular cartilage, and the thought is that a supplement will aid in the health of articular cartilage.
  • Intra-articular corticosteroid injections – may be useful for symptomatic ACL injury especially where there is a considerable inflammatory component. The delivery of the corticosteroid directly into the knee may reduce local inflammation associated with osteoarthritis and minimize the systemic effects of the steroid.
  • Intra-articular hyaluronic acid injections (HA) – injections are another injectable option for knee ACL injury. HA is a glycosaminoglycan that is found throughout the human body and is an important component of synovial fluid and articular cartilage. HA breaks down during the process of  ACL injury and contributes to the loss of articular cartilage as well as stiffness and pain. Local delivery of HA into the joint acts as a lubricant and may help increase the natural production of HA in the joint.

Surgical Treatment

ACL tears are not usually repaired using suture to sew it back together, because repaired ACLs have generally been shown to fail over time. Therefore, the torn ACL is generally replaced by a substitute graft made of tendon.

  • Patellar tendon autograft (autograft comes from the patient)
  • Hamstring tendon autograft
  • Quadriceps tendon autograft
  • Allograft (taken from a cadaver) patellar tendon, Achilles tendon, semitendinosus, gracilis, or posterior tibialis tendon

Patient Considerations

Active adult patients involved in sports or jobs that require pivoting, turning or hard-cutting as well as heavy manual work are encouraged to consider surgical treatment. This includes older patients who have previously been excluded from consideration for ACL surgery. Activity, not age, should determine if surgical intervention should be considered.

In young children or adolescents with ACL tears, early ACL reconstruction creates a possible risk of growth plate injury, leading to bone growth problems. The surgeon can delay ACL surgery until the child is closer to skeletal maturity or the surgeon may modify the ACL surgery technique to decrease the risk of growth plate injury.

A patient with a torn ACL and significant functional instability has a high risk of developing secondary knee damage and should therefore consider ACL reconstruction.

It is common to see ACL injuries combined with damage to the menisci, articular cartilage, collateral ligaments, joint capsule, or a combination of the above. The “unhappy triad,” frequently seen in football players and skiers, consists of injuries to the ACL, the MCL, and the medial meniscus.

In cases of combined injuries, surgical treatment may be warranted and generally produces better outcomes. As many as half of meniscus tears may be repairable and may heal better if the repair is done in combination with the ACL reconstruction.

Surgical Choices

There are 4 types of grafts

  • Autografts – are taken from the patient’s own body and include portions of the extensor mechanism patellar tendon, iliotibial tract semitendinosus tendon, gracilis tendon and menisci.
  • Allografts – grafts taken from cadavers.
  • Xenografts – grafts taken from animals. Bovine xenografts in particular have been associated with high complication rates.
  • Synthetics – These can be further classified into 3 categories, biodegradable (carbon fibers), permanent prostheses (Gore-Tex and Dacron), and ligament augmentation devices.

Patellar tendon autograft –  The middle third of the patellar tendon of the patient, along with a bone plug from the shin and the kneecap is used in the patellar tendon autograft. Occasionally referred to by some surgeons as the “gold standard” for ACL reconstruction, it is often recommended for high-demand athletes and patients whose jobs do not require a significant amount of kneeling.

The pitfalls of the patellar tendon autograft are

  • Postoperative pain behind the kneecap
  • Pain with kneeling
  • Slightly increased risk of postoperative stiffness
  • Low risk of patella fracture

Hamstring tendon autograft – The semitendinosus hamstring tendon on the inner side of the knee is used in creating the hamstring tendon autograft for ACL reconstruction. Some surgeons use an additional tendon, the gracilis, which is attached below the knee in the same area. This creates a two- or four-strand tendon graft. Hamstring graft proponents claim there are fewer problems associated with harvesting of the graft compared to the patellar tendon autograft including:

  • Fewer problems with anterior knee pain or kneecap pain after surgery
  • Less postoperative stiffness problems
  • Smaller incision
  • Faster recovery

Hamstring tendon autograft prepared for ACL reconstruction

The graft function may be limited by the strength and type of fixation in the bone tunnels, as the graft does not have bone plugs. There have been conflicting results in research studies as to whether hamstring grafts are slightly more susceptible to graft elongation (stretching), which may lead to increased laxity during objective testing. Recently, some studies have demonstrated decreased hamstring strength in patients after surgery.

There are some indications that patients who have intrinsic ligamentous laxity and knee hyperextension of 10 degrees or more may have increased risk of postoperative hamstring graft laxity on clinical exam. Therefore, some clinicians recommend the use of patellar tendon autografts in these hypermobile patients.

Additionally, since the medial hamstrings often provide dynamic support against valgus stress and instability, some surgeons feel that chronic or residual medial collateral ligament laxity (grade 2 or more) at the time of ACL reconstruction may be a contraindication for use of the patient’s own semitendinosus and gracilis tendons as an ACL graft.

Quadriceps tendon autograft

The quadriceps tendon autograft is often used for patients who have already failed ACL reconstruction. The middle third of the patient’s quadriceps tendon and a bone plug from the upper end of the knee cap are used. This yields a larger graft for taller and heavier patients. Because there is a bone plug on one side only, the fixation is not as solid as for the patellar tendon graft. There is a high association with postoperative anterior knee pain and a low risk of patella fracture. Patients may find the incision is not cosmetically appealing.


Allografts are grafts taken from cadavers and are becoming increasingly popular. These grafts are also used for patients who have failed ACL reconstruction before and in surgery to repair or reconstruct more than one knee ligament. The advantages of using allograft tissue include the elimination of pain caused by obtaining the graft from the patient, decreased surgery time and smaller incisions. The patellar tendon allograft allows for strong bony fixation in the tibial and femoral bone tunnels with screws.

However, allografts are associated with a risk of infection, including viral transmission (HIV and Hepatitis C), despite careful screening and processing. Several deaths linked to bacterial infection from allograft tissue (due to improper procurement and sterilization techniques) have led to improvements in allograft tissue testing and processing techniques. There have also been conflicting results in research studies as to whether allografts are slightly more susceptible to graft elongation (stretching), which may lead to increased laxity during testing.

Some published literature may point to a higher failure rate with the use of allografts for ACL reconstruction. Higher failure rates for allografts have been reported in young, active patients returning to high-demand sporting activities after ACL reconstruction, compared with autografts.

The reason for this higher failure rate is unclear. It could be due to graft material properties (sterilization processes used, graft donor age, storage of the graft). It could possibly be due to an ill-advised earlier return to sport by the athlete because of a faster perceived physiologic recovery, when the graft is not biologically ready to be loaded and stressed during sporting activities. Further research in this area is indicated and is ongoing.

Surgical Procedure

Before any surgical treatment, the patient is usually sent to physical therapy. Patients who have a stiff, swollen knee lacking full range of motion at the time of ACL surgery may have significant problems regaining motion after surgery. It usually takes three or more weeks from the time of injury to achieve full range of motion. It is also recommended that some ligament injuries be braced and allowed to heal prior to ACL surgery.

The patient, the surgeon, and the anesthesiologist select the anesthesia used for surgery. Patients may benefit from an anesthetic block of the nerves of the leg to decrease postoperative pain.

The surgery usually begins with an examination of the patient’s knee while the patient is relaxed due the effects of anesthesia. This final examination is used to verify that the ACL is torn and also to check for looseness of other knee ligaments that may need to be repaired during surgery or addressed postoperatively.

If the physical exam strongly suggests the ACL is torn, the selected tendon is harvested (for an autograft) or thawed (for an allograft) and the graft is prepared to the correct size for the patient.

After the graft has been prepared, the surgeon places an arthroscope into the joint. Small (one-centimeter) incisions called portals are made in the front of the knee to insert the arthroscope and instruments and the surgeon examines the condition of the knee. Meniscus and cartilage injuries are trimmed or repaired and the torn ACL stump is then removed.

Post-operative X-ray after ACL patellar tendon reconstruction (with picture of graft superimposed) shows graft position and bone plugs fixation with metal interference screws.

In the most common ACL reconstruction technique, bone tunnels are drilled into the tibia and the femur to place the ACL graft in almost the same position as the torn ACL. A long needle is then passed through the tunnel of the tibia, up through the femoral tunnel, and then out through the skin of the thigh. The sutures of the graft are placed through the eye of the needle and the graft is pulled into position up through the tibial tunnel and then up into the femoral tunnel. The graft is held under tension as it is fixed in place using interference screws, spiked washers, posts, or staples. The devices used to hold the graft in place are generally not removed.

Variations on this surgical technique include the “two-incision,” “over-the-top,” and “double-bundle” types of ACL reconstructions, which may be used because of the preference of the surgeon or special circumstances (revision ACL reconstruction, open growth plates).

Before the surgery is complete, the surgeon will probe the graft to make sure it has good tension, verify that the knee has full range of motion and perform tests such as the Lachman’s test to assess graft stability. The skin is closed and dressings (and perhaps a postoperative brace and cold therapy device, depending on surgeon preference) are applied. The patient will usually go home on the same day of the surgery.

Techniques for ACL reconstruction

Extra-articular reconstruction

Intra-articular reconstruction became the preferred choice but it does not fully restore knee kinematics by creating a static restraint and was usually accompanied by connecting the lateral femoral epicondyle to Gerdy’s tubercle with the collagenous restraint lying parallel to the intra-articular course of ACL. This also avoids the problem of lack of blood supply to the intra-articular reconstructions. Most of these procedures use the iliotibial band or tract connecting the lateral femoral epicondyle to the greedy tubercle, The optimal attachment point for the extra-articular reconstructions for anterolateral rotatory instability is found to be the Gerdy tubercle. This procedure is also used primarily in conjunction with an intra-articular reconstruction when severe anterior instability is due to injury or late stretching of the secondary stabilizing capsular structures or the lateral side of the knee.


  • Macintosh method (iliotibial band tenodesis)
  • Macintosh, modified by Loseen method
  • Andrews method


  • Diminish the anterolateral rotatory subluxation, but do not recreate the normal anatomy and function of the ACL.
  • When used alone has a high rate of failure.

Intra-articular Procedure

The advances made in the arthroscopy procedures have produced better results in ACL injury rehabilitation. This procedure may involve a small arthrotomy incision which preserves the vastus medialis oblique muscle to the patella. This procedure can be performed with both endoscopic technique or double incision arthroscopic technique.

Various tissues/grafts have been used to anatomically reconstruct the torn ACL which include portions of the extensor mechanism, patellar tendon, iliotibial tract, semitendinosus tendon, gracilis tendon, and menisci. These can all used in autografts i.e grafts taken from the person undergoing surgery. Other methods include the use of allografts and synthetic ligaments. This procedure has the following steps:

  • Graft selection – The graft to be used depends on the length of surgery. The most commonly used autograft is patellar bone graft and hamstring tendon graft (semitendinosus and gracilis).
  • Diagnostic arthroscopy – performed along with any necessary meniscal debridement or repair. Attention is given to partial-thickness tears, displaced bucket-handle tears, and the status of the articular surfaces, including the patellofemoral joint.
  • Graft Harvest – Mini incision extending from the distal pole of the patella to 2.5cm below the tibial tubercle is made to procure the graft. After retracting the other structures the graft to be taken is sharply outlined and a micro oscillating saw blade is used to harvest the graft/bone plug. A triangle bone plug profile is usually obtained.
  • Graft preparation – Graft is shaped into a 10mm tube shape for the femoral drill hole and an 11mm tube for the tibial tunnel.
  • Intercondylar notch preparation and notchplasty – Notchplasty is performed with 5.5mm burr from the anterior aspect of the intercondylar notch posteriorly and from distal to proximal and any residual tissue is also peeled off. The tissue is aggressively debrided with an arthroscopic shaver. If in the small intercondylar or notch area then further modifications are done.
  • Tibial tunnel placement – Tibial tunnel should be placed so that the graft is not impinged by the roof of the intercondylar notch and should reside within the middle third of the former ACL insertion site.
  • Femoral Tunnel placement – following a tibial tunnel placement, a femoral tunnel placement is completed so as to make a normal ACL like graft placement.
  • Graft placement – The graft after the tunnel placement is slid along with arthroscopic grasper through the tunnel. The graft may be rotated before tibial fixation.
  • Graft fixation – A Nitinol pin is then used to fix the graft with the bone and tunnel. The graft may be rotated before tibial fixation as an ACL has been shown to have external rotation within its fibers of approximately 90 degrees. The amount of graft tension created during fixation has a direct effect on ACL rehabilitation
  • Wound closure – Before closing, the graft harvest site is copiously injected with 0.25% Marcaine and it is also injected intra-articularly. The wound is closed with absorbable sutures with the knee in flexion. ACL reconstruction is one of the most common orthopedic surgeries, and commonly there is articular cartilage degeneration.
  • A total collateral ligament rupture and a full-thickness cartilage lesion would be seen on an MRI.
  • Patella tendon procedure: involves the central third of the ipsilateral patellar tendon. Fixation of the bone blocks within the tibia and femur.
  • Hamstring tendon procedure: four-layer, fold up of gracilis, and the semitendinosus tendons.

The surgery takes place at 10 weeks post-injury

Double-bundle reconstructionSemitendinosus is used with the autograft through 2 tunnels in both the tibia and femur. The autograft method is bone to bone with hamstrings/semitendinosus grafts. 3 tunnels may also be used, 2 tunnels through the tibia, and 1 tunnel through the femur.

The most common procedures for this reconstruction

  • The autologous bone to patella and tendon to bone graft
  • The autologous four-strand hamstrings graft

For the bone to patella and tendon to bone graft, a couple of bone blocks from the patella and the tibial tubercle are taken. This procedure causes more anterior knee pain than the semitendinosus graft. In the second procedure, the graft is obtained from the distal end of the semitendinosus and the gracilis tendon.

Other procedures are the LARS artificial ligament,(Ligament Advanced Reinforcement System) iliotibial tract allografts, cadaveric allografts, synthetic materials and grafts from living related donor people, but all materials have their drawbacks. There is the potential for cross infections, breakage, immunological responses, chronic effusions and recurrent instability

Single bundle vs Double bundle ACL reconstruction

A kinematics study showed that the standard single-bundle ACL reconstruction does not create the same kinematics as the intact ACL in normal activities. Only anteroposterior stability seems to be reconstructed. When the leg turns, there is an abnormal tibial rotation in the knee. Single-bundle ACL reconstruction does not recreate normal rotation in the knee.

On the contrary, anterior translation after double-bundle reconstruction was comparable with the intact ACL at 0° flexion, but the most stable position of the knee is at 15° and 75° flexion.

Watch this video to learn more about ACL Reconstruction using patellar tendon


Physical therapy is a crucial part of successful ACL surgery, with exercises beginning immediately after the surgery. Much of the success of ACL reconstructive surgery depends on the patient’s dedication to rigorous physical therapy. With new surgical techniques and stronger graft fixation, current physical therapy uses an accelerated course of rehabilitation.

Postoperative Course

  • In the first 10 to 14 days after surgery, the wound is kept clean and dry, and the early emphasis is placed on regaining the ability to fully straighten the knee and restore quadriceps control.
  • The knee is iced regularly to reduce swelling and pain. The surgeon may dictate the use of a postoperative brace and the use of a machine to move the knee through its range of motion. Weight-bearing status (use of crutches to keep some or all of the patient’s weight off of the surgical leg) is also determined by physician preference, as well as other injuries addressed at the time of surgery.


  • The goals for the rehabilitation of ACL reconstruction include reducing knee swelling, maintaining mobility of the kneecap to prevent anterior knee pain problems, regaining full range of motion of the knee, as well as strengthening the quadriceps and hamstring muscles.
  • The patient may return to sports when there is no longer pain or swelling, when full knee range of motion has been achieved, and when muscle strength, endurance, and functional use of the leg have been fully restored.
  • The patient’s sense of balance and control of the leg must also be restored through exercises designed to improve neuromuscular control. This usually takes 4 to 6 months. The use of a functional brace when returning to sports is ideally not needed after a successful ACL reconstruction, but some patients may feel a greater sense of security by wearing one.


  • Infection – The incidence of infection after arthroscopic ACL reconstruction is very low.  There have also been reported deaths linked to bacterial infection from allograft tissue due to improper procurement and sterilization techniques.
  • Viral transmission – Allografts specifically are associated with the risk of viral transmission, including HIV and Hepatitis C, despite careful screening and processing. The chance of obtaining a bone allograft from an HIV-infected donor is calculated to be less than 1 in a million.
  • Bleeding, numbness – Rare risks include bleeding from acute injury to the popliteal artery and weakness or paralysis of the leg or foot. It is not uncommon to have numbness of the outer part of the upper leg next to the incision, which may be temporary or permanent.
  • Blood clot – Although rare, blood clot in the veins of the calf or thigh is a potentially life-threatening complication. A blood clot may break off in the bloodstream and travel to the lungs, causing pulmonary embolism or to the brain, causing a stroke.
  • Instability – Recurrent instability due to rupture or stretching of the reconstructed ligament or poor surgical technique is possible.
  • Stiffness – Knee stiffness or loss of motion has been reported by some patients after surgery.
  • Extensor mechanism failure – Rupture of the patellar tendon (patellar tendon autograft) or patella fracture (patellar tendon or quadriceps tendon autografts) may occur due to weakening at the site of graft harvest.
  • Growth plate injury – In young children or adolescents with ACL tears, early ACL reconstruction creates a possible risk of growth plate injury, leading to bone growth problems. The ACL surgery can be delayed until the child is closer to reaching skeletal maturity. Alternatively, the surgeon may be able to modify the technique of ACL reconstruction to decrease the risk of growth plate injury.
  • Kneecap pain – Postoperative anterior knee pain is especially common after patellar tendon autograft ACL reconstruction. The incidence of pain behind the kneecap varies greatly in studies, whereas the incidence of kneeling pain is often higher after patellar tendon autograft ACL reconstruction.

Complications associated with non-surgical treatment are largely associated with NSAID use.

Common Adverse Effects of NSAID Use

  • Stomach pain and heartburn
  • Stomach ulcers
  • A tendency to bleed, especially while taking aspirin
  • Kidney problems

Common Adverse Effects of Intra-Articular Corticosteroid Injection

  • Pain and swelling (cortisone flare)
  • Skin discoloration at the site of injection
  • Elevated blood sugar
  • Infection
  • Allergic reaction

Common Adverse Effects of Intra-Articular HA Injection

  • Injection site pain
  • Muscle pain
  • Trouble walking
  • Fever
  • Chills
  • Headache

Complications Associated with HTO

  • Recurrence of deformity
  • Loss of posterior tibial slope
  • Patella baja
  • Compartment syndrome
  • Peroneal nerve palsy
  • Malunion or nonunion
  • Infection
  • Persistent pain
  • Blood clot

Complications Associated with UKA

  • Stress fracture of the tibia
  • Tibial component collapse
  • Infection
  • Osteolysis
  • Persistent pain
  • Neurovascular injury
  • Blood clot
  • Infection
  • Instability
  • Osteolysis
  • Neurovascular injury
  • Fracture
  • Extensor mechanism rupture
  • Patellar maltracking
  • Patellar clunk syndrome
  • Stiffness
  • Peroneal nerve palsy
  • Wound complications
  • Heterotopic ossification
  • Blood clot


Given the importance of neuromuscular factors and the etiology of ACL injuries, numerous programs have aimed to improve neuromuscular control during standing, cutting, jumping, and landing. [rx] The components of neuromuscular training are:

  • Balance training: balance exercises
  • Jump training – plyometrics: landing with increased flexion at the knee and hip
  • Strengthening that emphasizes proximal hip control mediated through gluteus and proximal hamstring activation in a close kinetic chain
  • Stretching
  • Skill training: Controlling body motions, especially in deceleration and pivoting maneuvers
  • Movement education and some form of feedback to the athlete during the training of these activities
  • Agility training: agility exercises

Examples of more recent neuromuscular training programs include: Sportsmetrics and Prevent Injury and Enhance Performance program. Both programs have a positive influence on injury reduction and improve athletic performance tests. [rx] The PEP plan includes: Warm Up, stretching, strengthening, plyometrics, and agility exercises. [rx]


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