The anterior cruciate ligament (ACL) is one of the two 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 tibial plateau and extends posteromedially to attach to the lateral femoral condyle. ACL and posterior cruciate ligament (PCL) together prevent excessive forward or backward motion of the tibia in relation to the femur during flexion and extension.
PREVALANCE: ACL sprains and tears are common knee injuries with a reported incidence of 100,000 to 200,000in the United States every year. ACL injuries are relatively common knee
injuries among athletes. It appears that females tend to have a higher incidence rate of ACL injury than males, that being between 2.4 and 9.7 times higher in female athletes competing in similar activities.
CAUSES: An ACL tear is usually sudden and is regularly seen in both contact and non-contact sports. It often occurs:
· As a result of cutting or pivoting maneuvers, when an athlete plants a foot and suddenly shifts direction.
· When a person lands on one leg, such as when jumping in volleyball or basketball.
· When the knee is hit directly, especially when it is hyper-extended or bent slightly inward.
· During a random slowing or stopping from running which can cause the ligament to hyper-extend.
· Through repeated stress to the knee, which can cause the ligament to lose elasticity (like a stretched-out rubber band).
· When the knee is bent backward or twisted, which can occur during a fall or landing a jump awkwardly.
RISK FACTORS: While everyone can injure their ACL, certain factors can put an individual at higher risk:
· Female sex. The rate of ACL injuries is three times higher in female athletes than in males.1 While the exact reason is unknown, some reasons include differences in muscle conditioning, control, and strength.
· Participation in certain sports. ACL tears commonly occur in sports such as basketball, soccer, football, volleyball, downhill skiing, lacrosse, and tennis. These sports require frequent and sudden deceleration, such as cutting, pivoting, or landing on one leg.
· Previously torn ACL. The risk of re-tearing a previously repaired ACL is approximately 15% higher than the risk of tearing a normal ACL.2 One study notes that this risk is highest in the first year after the initial injury. The risk of an ACL tear in the opposite knee is also higher once the injury has occurred in the first.
· Age. ACL tears are most common between the ages of 15 and 45, mostly due to the more active lifestyle and higher participation in sports.
· Occurs after either a cutting manoeuvre or single leg standing, landing or jumping
· There may be an audible pop or crack at the time of injury
· A feeling of initial instability which may be masked later by extensive swelling
· Episodes of giving way especially on pivoting or twisting motions. Patient has a trick knee and predictable instability
· A torn ACL is extremely painful, particularly immediately after sustaining the injury
· Swelling of the knee, usually immediate and extensive, but can be minimal or delayed
· Restricted movement, especially an inability to fully extend the knee
· Possible widespread mild tenderness
· Tenderness at the medial side of the joint which may indicate cartilage injury
Although ACL injury can be diagnosed clinically, imaging with magnetic resonance (MRI) is often utilized to confirm the diagnosis. %. Diagnosis may also be made with knee arthroscopy to differentiate complete from partial tears, as well as chronic tears. Arthrography is considered the gold standard as it is 92% to 100% sensitive and 95% to 100% specific; however, it is rarely used as the initial step in diagnosis as it is invasive and requires anesthesia.
On MR, ACL tears have primary and secondary signs. Primary signs will indicate changes associated directly with the ligamentous injury while secondary signs are changes that are closely related to the ACL injury. Primary signs include edema, an increased signal of the anterior cruciate ligament on T2 weighted or proton density images, discontinuity of the fibers, and a change in the expected course of the ACL (alteration of Blumensaat’s line). Tears usually occur within the midportion of the ligament, and signal changes are most often seen here and appear hyperintense. Secondary signs include bone marrow edema (secondary to bone contusion), Second fracture (as discussed below), associated medial collateral ligament injury, or anterior tibial translation of greater than 7 mm of the tibia relative to the femur (best seen on lateral view).
Radiographs are generally non-contributory for ACL injuries but are helpful to rule out fractures or other associated osseous injuries. In younger patients, avulsion of the tibial attachment may be seen. Other non-specific features that can be seen on radiographs include:
Second fracture: An avulsion fracture at the site of the lateral capsular ligaments/IT band insertion on the tibia
Arcuate fracture. An avulsion fracture at the proximal fibula at the site of the lateral collateral ligament and/or biceps femoris tendon
Deep lateral sulcus sign: A notch on the lateral femoral condyle with a depth of 1.5 mm or more, best seen on the lateral view
Computed tomography (CT) is not generally utilized in evaluating the ACL and is only accurate in detecting an intact ACL.
It depends on how badly you’ve been hurt. Here are some of the options your doctor may give you:
First aid. If your injury is minor, you may only need to put ice on your knee, elevate your leg, and stay off your feet for a while. You can reduce swelling by wrapping an ace bandage around your knee. Crutches can help to keep weight off your knee.
Medications. Anti-inflammatory drugs can help to reduce swelling and pain. Your doctor may suggest over-the-counter medications or prescribe something stronger. For intense pain, your doctor may inject your knee with steroid medication.
Knee brace. Some people with a damaged ACL can get by with wearing a brace on their knee when they run or play sports. It provides extra support.
Physical therapy. Once your physical therapist completes an initial evaluation and assessment, he or she will work with you to develop an appropriate treatment plan. Be sure to work closely with your PT to develop goals, and ask any questions if you do not understand your diagnosis, prognosis, or treatment.
Components of a physical therapy treatment plan after an ACL tear include, but are not limited to:
Pain control: Your physical therapist can use various treatment techniques to help decrease your knee pain. Ice packs may be used to decrease swelling, and occasionally TENS may be used on your knee to decrease the pain that you are feeling.
Gait training: If you are walking with an assistive device like crutches, your physical therapist can teach you how to use them properly. He or she can also help your progress from walking with crutches to walking normally with no assistive device.
Swelling management: The R.I.C.E. principle is one of the best ways to decrease swelling in your knee. This involves rest, ice, compression, and elevation of your knee.
Improving quadriceps contraction: After an ACL tear, your quadriceps muscle on the top of your thigh virtually shuts off and stops working properly. One of the main goals of physical therapy after a knee injury is to regain normal quadriceps control. Your physical therapist may use a form of electrical stimulation called NMES or Russian Stimulation to help accomplish this task. Quadriceps strengthening exercises, like straight leg raises, will also be prescribed.
Strengthening exercises: In addition to performing exercises to strengthen your quadriceps, other strengthening exercises for your hamstrings and hip muscles may be necessary during your ACL rehab.
Range of motion exercises: After an ACL tear, pain and swelling in your knee may limit your knee range of motion. Knee ROM exercises like the prone hang can be done to help improve and normalize your knee mobility.
Balance exercises: After a knee injury, you may notice you are having difficulty maintaining appropriate balance on your injured leg. Balance exercises using a wobble board or a BAPS board may be necessary to regain normal proprioception, or body awareness, after your injury.
Plyometrics: If you are planning on returning to high-level sports, then your physical therapy plan of care should include plyometric training. Learning to properly jump and land can help you regain the confidence needed to return to athletics.
One of the most important components of your ACL rehab program is to learn how to prevent future problems with your knee. Be sure to work with your physical therapist to determine the variables that may have contributed to your injury, and devise an exercise strategy to prevent another ACL injury.
Surgery: Your doctor may tell you that you need this if your ACL is torn badly, if your knee gives way when you’re walking, or if you’re an athlete. A surgeon will remove the damaged ACL and replace it with tissue to help a new ligament grow in its place. With physical therapy, people who have surgery can often play sports again within 12 months.
· Kolby and Kisner, Therapeutic exercises, 7th edition
· Adapted physical education and sport, Joseph P Winnick, Davil L Loretta, 6th edition
· The comprehensive manual of therapeutic exercises, Elizabeth Bryan, 2018