What is an ACL?

Three bones meet to form your knee joint: your thighbone (femur), shinbone (tibia), and kneecap (patella). Your kneecap sits in front of the joint to provide protection.

Bones are connected to other bones by ligaments. There are four primary ligaments in your knee. They act like strong ropes to hold the bones together and keep your knee stable.

These are found on the sides of your knee. The medial collateral ligament is on the inside and the lateral collateral ligament is on the outside. They control the sideways motion of your knee and brace it against unusual movement.

These are found inside your knee joint. They cross each other to form an “X” with the anterior cruciate ligament in front and the posterior cruciate ligament in back. The cruciate ligaments control the back and forth motion of your knee.

The anterior cruciate ligament (ACL) runs diagonally in the middle of the knee. It prevents the tibia from sliding out in front of the femur, as well as provides rotational stability to the knee.

ACL Diagram

What causes an ACL to tear?

ACL tears most commonly occur during sports that involve sudden stops, jumping or changes in direction — such as basketball, soccer, football, tennis, downhill skiing, volleyball and gymnastics. Many people hear or feel a “pop” in the knee when an ACL tear happens. Your knee may swell, feel unsteady and become too painful to carry weight.

complete ACL tear

What is an ACL Reconstruction?

Most ACL tears cannot be sutured (stitched) back together. To surgically repair the ACL and restore knee stability, the ligament must be rebuilt. Your doctor will renew your torn ligament with a tissue graft arthroscopically. This graft acts as a scaffolding for a new ligament to grow on.

Grafts can be obtained from various sources. Often they are taken from the patellar tendon, which runs between the kneecap and the shinbone. Hamstring tendons at the back of the thigh are also a very common origins of grafts. Sometimes a quadriceps tendon, which runs from the kneecap into the thigh, is used. Finally, cadaver graft (allograft) can be used. You should consult graft choices with your orthopaedic surgeon to help decide which is best for you. Because the regrowth needs time, it may be six months or more before an athlete can return to sports after surgery.

What to expect with Physical Therapy after an ACL Reconstruction?

Whether your treatment requires surgery or not, rehabilitation plays a necessary role in getting you back to your daily activities. A physical therapy program will help you regain knee strength and motion.

ACL Knee

If you have surgery, physical therapy first concentrates on returning motion to the joint and neighboring muscles. This is followed by a strengthening program intended to protect the new ligament. This strengthening steadily increases the stress across the ligament. The last phase of rehabilitation is a functional return to the athlete’s sport.

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