ACL Tears

What is the ACL?

The anterior cruciate ligament (ACL) of the knee is one of the ligaments attaching the femur to the tibia. It is in the central aspect of the knee. Its main function is to prevent forward motion (anterior translation) of the tibia in relation to the femur. It also aids in preventing hyperextension as well as internal and external rotation of the knee.

How is the ACL injured?

The ACL is primarily injured during landing, cutting and pivoting type activities. This explains its high association with sporting events such as basketball, soccer, football, and skiing. Injuries to the ACL can happen with or without external contact to the knee at the time of injury.

What are the symptoms of an ACL tear?

Tearing of the ACL can lead to pain, swelling, stiffness, and feelings of instability in the knee. The pain itself may not be localized to a single area of the knee. However, the ACL itself has very few pain fibers so some people may experience minimal pain and swelling if there are no other associated injuries.

How is an ACL tear diagnosed?

Diagnosis begins with a history and physical examination. Physical examination maneuvers such as the anterior drawer test, the Lachman test, and pivot shift test are used to test for ACL laxity. X-rays are used to evaluate the presence of a fracture associated with ACL tears (Segond fractures) or the presence of associated injuries. Finally, an MRI (magnetic resonance image) is used to give the highest quality image of the soft tissues of the knee, including the ACL.

Figure 1. Knee x-ray showing Segond Fracture consistent with ACL tear

Figure 2. Example of knee MRI with intact ACL

Figure 3. MRI example of knee with ACL tear

What are the treatment options for an ACL tear?

Treatment options are always individually tailored. Considerations include age, activity level, type of activity, how recent the injury occurred, partial versus complete tear, prior treatment, and associated injuries.

Historically, ACL reconstruction has been the gold standard for complete ACL tears. Due to the ACL's location within the knee it has been seen to have limited ability to heal. However, there is some data showing that in select patient populations conservative care with rehabilitation and bracing may be sufficient. There is data to suggest that conservative care does lead to inferior outcomes for children and adolescents. It should also be noted that in nearly all studies comparing outcomes between conservative and surgical care, the surgically treated knees showed increased stability. There are also small case series showing healing of ACL tears with the addition of biologics such as platelet rich plasma.

Surgical options for ACL tears include both ACL repair and ACL reconstruction. ACL repair attempts to heal the ACL tissue whereas ACL reconstruction removes the torn ACL and replaces this tissue with a graft. Determination of candidacy for repair versus reconstruction will depend on the age of the patient, location of the tear, quality of the remaining ACL tissue, and length of time from the injury.

Surgical repair is seen as an alternative to reconstruction due to the goals of limiting ACL graft harvest site morbidity and retaining the patient's native ligament. Typically repairs are ideal for young, active patients with proximal ACL ruptures or single bundle partial ACL ruptures. New advances such as the development Bridge-Enhanced Anterior Cruciate Ligament Restoration graft have attempted to expand these indications. Current outcomes of repair versus reconstruction show similar patient reported outcomes in the short and mid term but with a slightly higher retear rate in the repair group.

ACL reconstruction involves removal of the torn ACL with placement of an autograft (the patient's own tissue) or allograft (use of donor tissue). This treatment option results in improved stability to the knee after surgery, low re-tear rate, and high return to activity. However, rehabilitation and recovery are often extended, lasting six months to a year or longer in some cases.

Treatment options are similar for partial ACL tears. Consideration is given to patient age, percent of ACL tearing, location of ACL tearing, time from injury, laxity of the ACL on examination and activity level. Again, young more active patients trend to worse outcomes with conservative care of partial ACL tears. Surgical repair may serve a larger role in this cohort in comparison to reconstruction.

How is ACL repair performed?

The surgery is performed under a general anesthetic typically with the use of a regional nerve block. ACL repair is performed using an arthroscopically assisted method. It involves placing sutures within the remaining ACL tissue and then anchoring the tissue along with the Bridge Enhanced ACL Restoration collagen graft to both the femur and tibia. Attachment to the femur and tibia can be accomplished with either anchors or suture buttons with drill tunnels.

Figure 4. Example of ACL repair technique using the Bridge Enhance ACL Restoration graft (Shah et al. 2025)

How is ACL reconstruction performed?

The surgery is performed under a general anesthetic typically with the use of a regional nerve block. An ACL graft is prepared using either the patient's own tissue or donor tissue. Potential graft harvest sites include the quadriceps tendon, bone-patella tendon-bone graft, and hamstring. Currently, the majority of my patients undergo a quadriceps autograft ACL reconstruction. A drill tunnel is made in both the femur and tibia and the graft is then secured in the bone tunnels to allow for healing.

Figure 5. Step 1- Harvest and prepare quadriceps autograft. (Picture Credit: Arthrex.com)

Figure 6. Step 2- Drill femoral and tibial tunnels. (Picture Credit: Arthrex.com)

Figure 7. Step 3- Pass and seat the graft in bone tunnels. (Picture Credit: Arthrex.com)

Figure 8. Final graft fixation. (Picture Credit: Arthrex.com)

Graft options for ACL reconstruction

Two main groups of graft for ACL reconstruction include autograft (the patient's own tissue) and allograft (donor tissue). Advantages autograft include improved biologic fixation, lower retear rate, lower risk of rejection. Disadvantages include morbidity from the donor site, harvest site weakness, and harvest site recovery time. Use of allograft has the advantage of no donor site morbidity, shorter surgical time, and possibly reduced post operative pain. Disadvantages include slower biologic incorporation, high re-rupture rates, potential for immune response.

Common autograft harvest sites include the quadriceps tendon, bone-patella tendon-bone, and hamstring. The large majority of my current patients undergo quadriceps autograft reconstruction. Advantages include a larger graft size, potentially biomechanically stronger, and low graft site harvest pain. Disadvantages include possible donor site morbidity, recovery and graft defect.

Other possible procedures at the time of surgery:

Lateral Extra articular tenodesis- This procedure involves taking a portion of your iliotibial band and routing around the lateral collateral ligament of the knee and attaching to the femur. This adds additional constraint to the knee. This procedure may be added in cases depending on the patient's age, activity level, type of activity, and if this is a revision ACL reconstruction.

Figure 9. Example of Lateral Extra Articular Tenodesis. (Picture Credit: Arthrex.com)

Timing of ACL surgery

Many patients want to have surgery as soon as possible to hasten the recovery process. However, there is data to support attending physical therapy prior to surgery. This may be termed "prehab" and can lead to improved strength, functional outcomes, and return to sport after ACL surgery is completed. Some studies also suggest an extended delay to reconstruction may result in an increase in other soft tissue injuries. In some cases, certain associated injuries may preclude delaying surgery. Again, timing is on a case-by-case basis.

Outcomes of ACL surgery

Overall outcomes following ACL reconstruction are generally good to excellent. The following table, although from one study, shows a representation of expected outcomes. The scale is from 0 - 100 with 100 being a perfect score with no knee issues.

Figure 10. Table III from Marcaccio et al. JBJS REVIEWS 2023;11(10):e23.00057

Return to sport after ACL surgery

Readiness to return to sport after ACL surgery is multifactorial and depends largely on physical, psychological and neurological readiness. Although the outcomes of ACL surgery are generally good to excellent to return to sport rate varies depending on the series reported from ~70-90%. The rate of patients returning to the same level of activity is lower at ~50-60%. Although some patients have returned to sport as soon as 6 months after surgery, there is data to suggest that a return to sport after 9 months can reduce the reinjury rate.

What are possible complications of ACL surgery?

Infection

An uncommon complication reported rates range from 0.1% to 2.4%. Prevention at the time of surgery includes the surgical sterilization of the skin and using the use of antibiotics at the time of surgery. Presentation of infections could include fever, chills, increased pain and swelling at the surgical site, redness, warmth and drainage. Management often includes antibiotics and possibly surgical irrigation and debridement.

Graft Failure

Incidence of graft failure ranges from 2-10% depending on the series reported and graft selection. Prevention includes appropriate surgical technique, rehabilitation, recovery and timing to return to activity. Treatment of graft failure includes revision ACL reconstruction.

Knee Stiffness

Knee stiffness results from scar tissue formation leading to restricted range of motion and can occur in up to 5-10% of cases. Prevention includes timing to surgery and accelerated rehabilitation protocols. Treatment of knee stiffness includes rehabilitation, surgical lysis of adhesions and manipulation under anesthesia.

Deep Venous Thrombosis (Blood clot)

Although typically rare with reports being lower than 1% of cases, there are studies reporting asymptomatic blood clots in up to 15% of ACL cases. Presentation of a blood clot can include increased pain and swelling in the leg with diagnosis confirmed with an ultrasound. Prevention includes early immobilization, possible use of compression stockings, and possible use of chemical prophylaxis such as aspirin. Treatment typically includes use of anticoagulation medications such as lovenox or apixaban.

Nerve injury

Nerve injury is uncommon after ACL surgery. Most common type of nerve injury includes numbness around incision sites. This usually resolves with continued observation. In rare case pain management may be required to aid in symptom management.

Hardware Irritation

Hardware is used to secure the ACL graft to the femur and tibia. Uncommonly this hardware can cause continued pain in the area it is located. This can present as localized pain and swelling at the hardware sites. In such cases the hardware may need to be surgically removed once the graft has fully healed.

Anterior Knee Pain

Persistent anterior knee pain has been historically been associated with bone patella bone graft harvest with rates up to ~40%. Although still possible with hamstring or quadriceps autograft harvest the rates seen are typically much lower with series usually showing rates > 10%. Treatment can include physical therapy, bracing, taping, or possible injections.

Osteoarthritis

Osteoarthtis development after an ACL injury is multifactorial and ultimately related to cartilage injury. Some studies report up to 50% of patients may develop arthritis of the injured knee within 15 years of the injury, although not all of these cases are symptomatic. Prevention includes rehabilitation focusing on quadriceps strengthening and resorting joint mechanics and stability. Treatment may include anti inflammatory medications, injection therapy, rehabilitation and possible joint preservation surgery.

This is not an exhaustive list of all complications. Other complications, although uncommon, can still occur.

What will help my pain after surgery?

Medications including narcotic pain medications and anti inflammatories may be prescribed after surgery to help reduce pain. Nerve blocks at the time of surgery have been shown to be affective at reducing pain with low risk of long term deficits. Additionally, use of cold compression devices have been shown to reduce pain and need for pain medications.

Are there other modalities that can improve my healing after ACL surgery?

There are studies that show use of biologics such as platelet rich plasma can decrease of knee arthrofibrosis and increase speed for graft incorporation into bone after surgery. This can be injected at the time of surgery or after.

Neuromuscular Electrical Stimulation is used during knee rehabilitation to aid in muscle fiber recruitment. This can be applied both at home and during physical therapy sessions.

Use of blood flow restriction therapy involves use of a tourniquet like cuff placed on the lower extremity during exercise. Use of blood flow restriction therapy with low intensity exercise allows lower knee joint pain in comparison to high intensity training without blood flow restriction. This will be used during physical therapy sessions. Check with your physical therapy location if they have this modality available.

Supplement recommendations are often sought after surgery. There is low evidence to support the use of protein supplementation after ACL surgery. No evidence is available to provide recommendations for a particular protein supplement. No significant evidence is available to support creatine supplementation or vitamin supplementation.

Hyperbaric oxygen therapy has long been studied in regard to wound healing. Studies show improved wound healing with the use of hyperbaric oxygen therapy. There is limited data specifically in regard to ACL or knee injuries with hyperbaric oxygen therapy, although there is some animal data to support the use for increased graft incorporation, maturation and healing. There are no specific number of treatments or specific protocols that can be recommended at this time. Hyperbaric oxygen therapy centers are available in Austin.

Do I need to use a brace after ACL surgery?

In the immediate post operative period you will use a knee brace. The use of a knee brace that can lock in extension can prevent knee buckling while walking in the immediate post operative period . It can also be used to prevent excessive knee flexion if other procedures, such as meniscus repair, require limited knee range of motion.

The use of knee bracing when return to sport is controversial. Functional knee bracing has been shown to have benefits in proprioception and limb symmetry. However, clinical studies show no significant benefit in functional stability, patient reported outcomes or retear rates. In contrast there is data to support lower retear rates in skiers post ACL surgery. Your use of a brace will largely be determined on subjective stability, sporting type and activity level.

When can I return to work after surgery?

Return to work will largely depend on your specific occupational requirements. Many patients are no longer requiring the use of pain medications during the day by the fifth day after surgery. If your work is sedentary, you may be able to return as soon as this time. If you are required to stand for a significant period during the day return to work may need to be delayed until you are off crutches. This may be from week 1-6 after surgery depending on other concomitant procedures such as meniscus repair performed. Work that involves heavy lifting may require longer periods away from work if light duty is not available.

When can I drive after surgery?

There is no definitive test we can do to determine when a patient is safe to return to driving. You should not be taking narcotic or sedating medications prior to driving. Studies attempting to look at when it is safe to return to driving have looked at brake response times. In general, brake response time has been shown to return to normal by 4-6 weeks after right sided ACL surgery and 2-3 weeks after left sided ACL surgery. Procedures that result in delayed weight bearing, such as meniscus repair, will likely delay return to driving.

Post operative Instructions

• Following your stay in the recovery room and when your vital signs are stable you will be discharged to your escort.
• Remember, it is normal to feel a little dizzy or drowsy for several hours after surgery. This is due to the action the medicine used during surgery.
• If you do not have a post operative appointment scheduled, please call the office as soon as possible to schedule this appointment.
• Take your pain medicine as directed. Begin the pain medicine before you start getting uncomfortable, as the nerve block will wear off. If you wait to take your pain medication until the pain is severe, you will have more difficulty in controlling the pain.
• Take 1 tablet (81 mg) of aspirin per day, starting the day after surgery and continuing for 4 weeks. The risk of blood clots is quite low after ACL surgery but aspirin is taken as a precaution to decrease the risk. Certain factors such as smoking, birth control pills and certain medical conditions increase the risk of blood clots and it is especially important to take the aspirin for those situations. If you were previously on a blood thinner you will resume this medication, rather than starting aspirin, beginning the day after surgery.
• If you are taking narcotic pain medication you may need a stool softener to prevent constipation. Over-the-counter medication such as Docusate or Milk of Magnesia is recommended.
• Notify the office of any fever, chills, or temperature > 100.5.
• Notify the office of any wound drainage.
• You can begin the home exercises listed below the day after surgery. Perform the ankle pumps periodically, throughout the day. The remainder of the exercises can be performed once at least once a day.

Post-Surgery Diet

Resume your diet as tolerated and include vegetables, fruits, and proteins (such as meats, fish, chicken, nuts, and eggs) to promote healing. Also, remember to have adequate fluid intake. It is common after surgery to lack an appetite. This may be the result of anesthesia and the medications. Proper nutrition is needed for healing. During the healing process, the body needs increased amounts of calories and protein. Eat a variety of foods to get all the calories, proteins, vitamins, and minerals you need. If you have been told to follow a specific diet, please follow it.

If you're not eating well after surgery, contact your healthcare provider about nutritional supplements.

How should I manage my surgical site and bandages?

You can remove your surgical dressing on the third day after your surgery. You will remove everything except the Steri-strips if present. See picture below for example of Steri strips.

Allow the steri-strips to fall off on their own. If necessary, sutures will be removed at your first post-operative visit.

Example of Steri strips:

You may shower with a waterproof bandage covering the incisions in three days. Example of waterproof bandage shown in picture below. These can typically be purchased at CVS or Walgreens. Keep the incisions dry until the Steri strips fall off or are removed in clinic. Try not to let the direct spray of water from the showerhead hit the incision.

You can cover your incision with a bandage if needed to prevent irritation with clothing.

A small amount of drainage from the surgical sites is common. If this occurs, you may apply a bandage to the affected area.

Leakage immediately after surgery is normal and helps to drain some of the fluid that accumulates in the joint during surgery.

The dressings may become moist or blood-stained; this is normal and not typically a cause for alarm.

Example of waterproof bandage:

Do I need to wear a knee brace?

You will use a knee brace such as this:

Instructions for fitting and adjustment can be found at:

https://www.breg.com/products/knee-bracing/post-op/t-scope-premier-post-op-knee-brace/

You will lock the brace straight when walking but can unlock the brace at rest. The prescribed range of motion settings will be set in the operating room.

You may remove the knee brace for exercises as prescribed by the surgeon/therapist, icing, dressing, and showering.

What is my activity level after surgery?

You will use crutches to aid with walking after surgery.

Elevate the operative leg to chest level whenever possible to decrease swelling. Do not place pillows under knees (i.e. do not maintain knee in a flexed or bent position) but rather place pillows under foot/ankle.

Do not engage in activities which increase knee pain/swelling (prolonged periods of standing or walking) over the first 7-10 days following surgery.

Avoid long periods of sitting (without leg elevated) or long distance traveling for 2 weeks.

Physical therapy should begin by post-operative day 5 or sooner.

You can begin motion of your ankle and toes now.

How do I use my ice machine?

Use of cold compression can help with post operative pain and swelling after surgery. One example is the following:

Instructions for use can be found at:

https://www.breg.com/products/cold-therapy/devices/polar-care-wave/

If you have another machine please check that manufacturer's website for use instructions.

Use every waking hour for 15 minutes for the first 24 hours. After this time you can use the machine at least three times a day for 15 minutes.

Do not sleep with the automated device on.

Keep a layer of fabric between the skin and icing device at all times.

How do I use the neuromuscular electrical stimulation?

An example of an NMES machine includes:

Instructions for use can be found at:

https://www.zynex.com/products/nexwave/

Electrodes will be placed at the quadriceps. For example:

With the knee in extension, increase the stimulation amplitude until contraction of the quadriceps is visualized. Increase amplitude to your tolerance level. Contractions should last 10 seconds with 30-50 second rest periods between contractions. This can be started once the bandages are removed on the third day after surgery. This can be performed at least 5 days a week for one hour per day.

Can I smoke following surgery?

You should not smoke after surgery as it interferes with healing.

Questions or Concerns

If at anytime you have questions or concerns you can either contact your surgeon's medical assistant via email or you can call the main office numbers at: 855-624-3306. You can also use the electronic medical record's online portal to send questions.

Exercises you can perform at home at this time:

Straight Leg Raise

While lying on your back, raise up your leg with a straight knee. Keep the opposite knee bent with the foot planted on the ground.

Short Arc Quad

Place a rolled up towel or object under your knee and slowly straighten your knee as you raise up your foot.

Heel Slides- Supine

Lying on your back with knees straight, slide the affected heel towards your buttocks as you bend your knee. Hold a gentle stretch in this position and then return to original position.

Ankle Pumps

Bend your foot up and down at your ankle joint as shown.

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