The Anterior Cruciate Ligament (ACL) is considered the most important of four major ligaments located in the knee, providing about 90% of the knee's stability. It attaches at the front of the tibia (main shin bone) and back of the femur (thigh bone) to prevent excessive forward motion of the lower leg as well as provide stability during twisting and planting activities.
The ACL is located in the center of the knee just in front of the Posterior Cruciate Ligament (PCL), which keeps it from moving too far backward. Although the ACL is often injured among athletes it is not uncommon in the non-athletic population. ACL tears are more common among women likely due to numerous factors, including wider hip angle, increased joint laxity and hamstring-quadriceps strength imbalances.
How is the ACL/PCL Injured?
Knee movements that place great amounts of strain on the ligament can cause an ACL injury. The most common mechanism is pivoting on the knee with the foot planted, such as cutting while slowing down from a sprint. The second mechanism that often causes damage to the ACL is knee hyperextension where the knee is pushed farther straight than it should go. For example, landing from a jump with a straight leg in basketball. The final mechanism of injury is wear and tear, in which little tears have accumulated in the ACL over time. These little tears weaken the ligament and one small stress can result in a complete tear. People often hear a pop when an ACL injury takes place, but the absence of a pop does not rule out a tear.
PCL injuries are likely to occur as a result of front impact sustained by the knee or when the knee is hyper-extended. Whereas ACL injuries mostly sustained from sports activities that do not require physical contact, PCL injuries are mostly the end result of a forceful collision with the knee.
Surgical and Non-surgical Options
After any injury, it is best to first consult with your primary physician. He or she may perform several knee stability tests and order an X-Ray or MRI. Once a diagnosis of ACL tear is made, the patient and doctor will determine if surgery is appropriate. A torn ACL cannot simply be sutured back to the bone; instead, it is necessary to completely replace the injured ligament with a tendon from another area of the body or external source.
EARLY REHABILITATION PHASE: (1-2 weeks after surgery or injury)
Immediately after surgery or injury, it is important to apply the P.R.I.C.E. principles to reduce swelling and pain. P.R.I.C.E. stands for Protection, Rest, Ice, Compression, and Elevation. Your physical therapist is important at this time to move your knee through different range of motion sequences and begin early strengthening activities, such as quad sets.
SECOND REHABILITATION PHASE: (3 to 4 weeks after surgery or injury)
During this phase, pain will significantly decrease and it becomes important to protect the knee against over-activity. Rehabilitation will focus on regaining range of motion. Patients will begin to do balance activities, perform exercises in the pool or ride a stationary bike. Strengthening exercises will be progressed to include activities such as wall squats, step-ups and the leg press machine.
CONTROLLED AMBULATION PHASE: (4 to 6 weeks after surgery or injury)
The main goal during this phase is to bend the knee to at least 130 degrees. To achieve this goal, new exercises will be introduced and previous exercises will be progressed. For example, squats will be progressed from two to only one leg and step-ups will be performed on a larger step. A home exercise program will be emphasized and will help you continue to improve your range of motion and strength outside of the clinic. Your physical therapist will make a printed handout of all of your exercises in order to remind you of correct form and technique.
PROTECTION PHASE: (6 to 8 weeks after surgery or injury)
Full range of motion should be achieved. Exercises, both in the clinic and at home, will continue to be progressed by your physical therapist.
LIGHT ACTIVITY PHASE: (8 to 10 weeks after surgery or injury)
During this phase, the emphasis is on balance and functional movement. Examples of exercises include lunges, squats on a BOSU, quick step touching, step downs and different stepping patterns with a sport cord.
FUNCTIONAL ACTIVITY PHASE: (10 weeks or more after surgery or injury)
Rehabilitation will continue until all of your goals are met and you are able to return to your pre-injury lifestyle. Jogging on a treadmill and agility drills are common in this phase. Other exercise examples include grid touching, box jumping, tossing a ball while balancing on one foot and hopping. Finally, if necessary, this is a good time for a patient to be fitted for a sport brace.
ACL Rehabilitation Expectations and Timetable
Each person's recovery time is different. Factors, such as age, extent of injury, type of surgery, work ethic during rehab and overall health and fitness can drastically affect how long recovery will take. Rehab following the traditional ACL repair surgery often takes 6 to 9 months until full strength and function are restored. Light jogging and running in a straight line are usually seen at about 4 months after surgery. The rule of thumb to return to sports is that the recovering knee must have at least 90% of the strength of the opposite leg. Some doctors are now performing an accelerated surgery that can put the athlete back on the playing field in 6 months. It is necessary to consult with your physician before exploring this option.