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What is the ACL and how is it injured?

The ACL, anterior cruciate ligament, is one of the 4 main ligaments of the knee that keeps the knee stable. The ACL is found in the center of the knee and it attaches the femur to the tibia. It limits forward motion of the tibia as well as rotation. The ACL is usually injured with a twisting injury to the knee or a direct blow to the outside of the knee with a contact or non-contact mechanism. A contact injury may involve being hit by an opponent in sports such as football. The ACL is also commonly injured with a non-contact twisting injury in sports such as soccer, basketball or skiing.

What are symptoms of an ACL tear?

Acute Chronic
Marked pain and “feeling a pop” Your knee “feels loose”
Significant knee swelling Feelings of “buckling”, “giving way” or instability
Difficulty bearing weight on affected knee Pain and swelling

Other signs and symptoms can be dependent on injuries to other knee structures, such as the MCL, PCL, posterior lateral corner, medial meniscus, lateral meniscus, or articular cartilage.

If your doctor suspects an ACL injury by history and physical exam, he will often order a MRI. This is the best test for evaluating the ACL as well as the meniscus, articular cartilage, and other knee ligaments.

How do we treat ACL tears acutely?

  • Rest
  • Ice
  • Elevation
  • Compression
  • Protected Weight Bearing
  • Brace

Does everyone with a torn ACL need surgery?

No! We do not recommend ACL reconstruction in patients with advanced arthritis, patients who do not perform activities that require an ACL (i.e. older, less active patients), and patients who cannot commit to a post-operative rehab program.

Who does need an ACL reconstruction?

Most patients do require ACL reconstruction. Most young, active patients with an otherwise healthy knee require ACL reconstruction. Patients without advanced arthritis who experience recurrent buckling or giving way need reconstruction to restore stability and function.

What are ACL-dependent activities?

ACL-dependent activities Non-dependent activities
Cutting sports- basketball, soccer, football, softball, tennis, cheerleading, skiing, etc. Walking
High-end aerobics Jogging in a straight line
Skateboarding Desk jobs
Difficult hiking Riding a bicycle
Most laboring jobs
Any activity that results in the knee buckling during or after the activity

Who needs a pre-op brace?

Patient’s whose knee buckles (gives out) with everyday activities.

What are the risks of not getting your ACL reconstructed?

Every time your knee buckles, you risk injuring other vital structures of your knee such as the meniscus, ligaments, or articular cartilage. If these structures get injured, it could lead to rapidly-accelerated arthritis.

Are there any pre-operative requirements for ACL reconstruction?

Yes, you should have normal or near-normal knee range of motion. Sometimes, patients go to physical therapy pre-operatively to get their range of motion restored before surgery. The best predictor for post-operative range of motion is pre-operative range of motion.

What should I do before my surgery?

Avoid activities that make your knee buckle, understand your injury, be sure to ask your surgeon any questions that you may have, understand the expected post-operative course, and choose a graft with your surgeon. ACL’s are not repaired but rather reconstructed and, thus, require other tissue for a graft.

How does my surgeon pick a graft?

A graft that can be made from your own tissue is called an autograft. It can either be a bone-patellar tendon-bone (BTB) autograft or a hamstring autograft. The BTB is made using a bone plug from your knee cap, middle 1/3 of your patellar tendon, and a bone plug from your shin bone. The hamstring autograft is made from 2 of your hamstring tendons. This is less painful than the bone patellar tendon bone graft and still allows for a very stable knee. This is the graft of choice for patients with open growth plates.

A graft that can be made from cadaver tissue is called an allograft. These grafts are the least painful and require the smallest incision. This is recommended in patients with significant injuries to other ligaments of the knee and usually in revision cases. In most cases, there is a very small risk of disease transmission from the donor.

Graft choices are personal choices and should be discussed with your surgeon. There is no convincing evidence in the orthopaedic literature stating that one graft is any better than the other.

How is ACL surgery performed?

First, the anesthesiologist administers a nerve block in pre-op that typically lasts between 12- 18 hours. You are then placed under general anesthesia and your knee is examined to test your knee without muscle resistance. The camera is then placed into your knee using a small incision. A complete inventory of your knee is performed looking at all the structures in your joint. Additional portals are made for the insertion of the working instruments. If your surgeon sees any abnormalities, these are addressed at this time. Depending on which graft is used, your graft is harvested and prepared to become your new ACL. Tunnels are then drilled in your femur (thigh bone) and tibia (shin bone) which is where your new ACL is placed. The graft is passed across the knee and surgical devices are used to hold the graft in place while it heals to the bones.

When you wake up, your knee will be in a dressing and in a long brace locked in full extension (straight out). Your incisions are stitched together and white steri-strips are placed over your incisions. Keep your dressing clean, dry, and intact for 3 days post-op. You can shower post-op day 3, scrubbing your thigh and letting the soapy water run over your incisions. Do not scrub your incisions. You will be sent home with pain medication and a medicine for nausea.

Complications of ACL reconstruction occur infrequently but can include and are not limited to bleeding, infection, persistent or increased pain, damage to nerves, blood vessels, or cartilage, worsening condition, DVT, recurrent instability, stiffness, or need for reoperation.

Post-Op Rehabilitation

In most cases, you can go home the same day. If the pre-op block worked you will be comfortable but be sure to take your pain medication when you get home before your block wears off. You wake up in a brace which is to be worn at all times you are not seated or lying. We recommend sleeping in your brace. Ice the affected knee. Elevate your knee above your heart as much as possible. You may weight bear on your leg as you can tolerate immediately post-op with the assistance of crutches, unless directed otherwise by your surgeon. You can take all your dressings down except for the steri-strips (white band aid like strips) on the third day after surgery and take a shower. Do not scrub or soak your wounds. Wash your thigh with soap and water and let the soap and water run off and pat your wounds dry. If your wounds are dry, you may leave them open to the air or put a clean dry dressing over them. Do no put any creams or ointments on your wounds (i.e. polysporin, etc). Follow up with your surgeon 3-5 days post-op.

Physical therapy is prescribed to restore your motion and strength. The amount of therapy that you will need depends on what surgery was performed. Physical therapy is very important in optimizing your outcome. It is hard to estimate when you can return back to work or sport, as each surgery is highly variable. It is important to anticipate the expected length of recovery; it often can be estimated before surgery. This may vary based on the surgery performed, abnormalities found during surgery, or your specific sport or occupation.

You may be on crutches for 7-14 days. You can wean off your crutches with the help of your physical therapist when your quad muscle wakes up and you can hold a straight leg raise for 10 seconds. You can go to school when you are off narcotics and able to navigate school with your brace on and locked. This is usually between 5-7 days. You can go back to work unrestricted at a labor job in 6-9 months after your knee is fully healed. You can return to a desk job typically in 7-14 days after your pain goes down and you’re off narcotic pain medicine.

Physical therapy after ACL surgery initially consists of range of motion exercises and very gentle quad exercises. Physical therapy is 2-3x per week. Your therapist will tell you when safe to get off crutches based on your quad strength. At 1 month post-op, your therapist can shorten and unlock your post-op brace and you continue therapy 2-3x per week. At 2 months, you’re given a hinged knee sleeve and you begin aggressive quad strengthening exercises (0-90°- bike, elliptical, stair climber, squats, lunges). Many of these exercises can be done on your own at a gym or at home. We still recommend checking in with your therapist periodically for them to “coach” you on your exercises and make sure you are on the right track. At 3 months, you can begin to jog in a controlled environment with no cutting or side-to-side movements if your quad muscle is progressing appropriately. At 4-5 months, you can begin some sport-specific activities. At 6-9 months you can return to sport/work. The post-op course varies between patients and your course may be slightly different.

ACL rehab cannot be accelerated. We cannot change biology and how fast humans heal. It takes several months for your new graft to grow into the bone. Accelerated rehab risks stretching your graft and making it too loose and non-functional. The length of your rehab is based more on the strength of your quad than on the knee. The thigh (quadriceps muscle) shuts down (goes to sleep) after surgery and it takes time and rehab for it to wake up. It takes 6-9 months for the quadriceps musculature to fully restore itself after surgery. Until the thigh muscle is strong again your knee will feel loose even though it is entirely stable. The more frequently you can do your quad exercises, the faster the quad will be strong and the faster you may safely return to full activities.

Find out more about ACL Reconstruction Using Hamstring Tendon by clicking on the following link:

Find out more about ACL Reconstruction Using Patellar Tendon by clicking on the following link: