The town is buzzing with excitement over the recent snowfall here in the Vail Valley! While we wish everyone a safe winter season, with just 52 days until the opening of Vail Mountain, we want our winter enthusiasts to be informed about ACL injury and what to expect if you experience a forceful twisting injury to the knee…

The ACL

The anterior cruciate ligament, or ACL, is one of four major ligaments that provide stability to the knee joint.  ACL injuries are very common among athletes of all ages and competition levels with approximately 200,000 reported cases in the United States each year.  Skiing, soccer, football and basketball are activities in which we see a higher incidence of ACL injuries due to the cutting and pivoting nature of these sports.  The ACL provides stabilizes the knee preventing giving way episodes and instability of the knee joint. When the ACL tears, the knee joint subluxates and this commonly results in a tear of the either the medial or lateral meniscus, which are the shock absorber cartilages in the knee.

Causes of ACL injury

When skiing, ACL injuries most often occur as the result of a “slip-catch” mechanism.  In this scenario, the skier is typically in the back seat, the downhill leg is fairly straight when the downhill ski catches the snow, forcing the knee into a valgus, or inward collapsing, position with internal rotation of the tibia and the ACL tears.  Other common causes of ACL injury when skiing include landing in the “backseat” with the knee bent or a forceful snow plow mechanism.  Many skiers report feeling a sudden pop or tear at the time of injury.

After the injury

So you’ve caught your edge and felt a pop to the knee, now what?  Following an ACL injury patients often report feelings of immediate pain and instability upon standing or that the knee will “give out” when trying to place their boot back in the binding.  While some skiers may be able to make it down the mountain under their own power, others may require the assistance of ski patrol with a toboggan.  Skiers who find themselves in the mountain base clinic or emergency department will likely undergo a series of X-rays as well as physical exam so that the emergency physician can make a diagnosis and refer you to an orthopaedic specialist.  If X-rays are negative for a fracture, the patient may bear weight as tolerated, but may require crutches.  You will most likely be placed in a knee brace, provided with pain medications for comfort, told to ice and elevate, and referred to the appropriate specialist for follow up evaluation and recommendations for treatment.

Knee evaluation

Specialized orthopaedic evaluation includes a series of ligamentous knee tests to assess the four major ligaments of the knee.  The Lachman’s test and Pivot Shift test are used to assess the status of the ACL. If a Lachman test is positive, there is increased anterior translation of the tibia in relationship to the femur. If a Pivot Shift Test is positive, there is increased rotational instability of the tibia in relationship to the femur.  There is typically point tenderness on the lateral joint line. If there is point tenderness to the medial joint line with positive McMurray’s or Thessaly’s testing there may be a medial meniscus tear. Following this series of clinical tests, MRI imaging is obtained for a definitive diagnosis.  This will also help determine if there is additional injury to the knee such as meniscus tears, another injured ligament or articular cartilage injury. The MRI is very helpful for pre-surgical planning.

ACL reconstruction

After confirming a torn ACL, it is not uncommon that your orthopaedic sports medicine specialist will recommend reconstructing the ligament so that you can return to cutting and pivoting sports such as skiing without continued feelings of instability.  An ACL reconstruction is recommended for young or active patients and in almost all patients who report instability to the knee with cutting or pivoting activities.  This surgery is done arthroscopically, and key to a successful surgery is for the ACL graft to be placed exactly where your original ACL was on the femur and tibia.  Dr. Cunningham recommends that younger, active people have an autograft tendon, meaning a tendon from you, used to reconstruct your ACL, as allograft or donor tendon grafts tear at a higher rate. Dr. Cunningham typically recommends using a portion of  patient’s hamstring or quadriceps tendons.  Another graft choice is bone-patellar tendon-bone autograft, but Dr. Cunningham typically recommends a quadriceps graft over a patellar tendon graft as it is thicker and less painful.

After surgery

Following ACL reconstruction surgery, pending other necessary repairs, we allow patients to walk on the knee right away, full weight bearing through the surgical lower extremity locked in a telescoping knee brace for 2 weeks.  Crutches may be required for the first few days following surgery and a cold-compression unit is often recommended.  Pain medications are prescribed initially post surgically for pain control and physical therapy can begin right away to work on range of motion and joint mobilization.  The knee brace is discontinued approximately 2 weeks from the date of surgery or when the quadriceps muscle demonstrates good activation while walking.  We anticipate full range of motion of the knee by 6 weeks post-operatively at which time patients can increase their strengthening program with the guidance of a skill physical therapist.  Formal therapy is recommended over a time frame of approximately 3-4 months in addition to a home exercise program.  A patient may begin jogging at 3 ½ months post-op and begin to increase their activities as tolerate with pain and swelling as their guide, however we continue to recommend avoidance of cutting and pivoting sports such as soccer, skiing, football or basketball until approximately 8-9 months post-operatively.  At that time we fit our patients for a functional knee brace for full clearance to return to sport.

Have you experienced a twisting injury to your knee?  Do you think you’ve torn your ACL?  We’re happy to see you!  For more information regarding ACL injury and Dr. Cunningham’s surgical technique feel free to visit our website at www.vailknee.com, watch one of our youtube videos on youtube, or give our office a call to schedule an appointment at 970-569-3240 (Edwards) or 970-668-3633 (Frisco).

Authors: Richard Cunningham M.D. and Victoria Stanislawski, ATC.