What is an anterior cruciate ligament (ACL) sprain? A sprain is a joint injury that causes a stretch or a tear in a ligament. Ligaments are strong bands of tissue that connect one bone to another. The anterior cruciate ligament (ACL) is one of the major ligaments in the middle of the knee. It connects the thigh bone (femur) to the shin bone (tibia). This ligament, along with the posterior cruciate ligament, helps keep the knee stable and protects the femur from sliding or turning on the tibia. Sprains are graded I, II, or III depending on their severity: Grade I sprain: pain with minimal damage to the ligaments. Grade II sprain: massive ligament damage and mild looseness of the joint. Grade III sprain: the ligament is completely torn and the joint is very loose or unstable.

How does it occur? The ACL is frequently injured in forced twisting motions of the knee. It may also become injured when the knee is straightened further than it normally can straighten (hyperextension). It sometimes occurs when the thigh bone is forcefully pushed across the shin bone, such as with a sudden stop while you are running or a sudden transfer of weight while you are skiing.

What are the symptoms? There is usually a loud, painful pop when the joint is first injured. This is often followed by a lot of swelling of the knee within the first several hours after the injury. This swelling is called an effusion and is made up of blood in the knee joint.

How is it treated?After examinationan MRI scan is done to clearly show the condition of the ACL. As in any injury, the immediate treatment is to minimize and limit the amount of inflammation by R.I.C.E (Rest, Ice, Compression, Elevation) and anti-inflammatory drugs. For grades I & II, hot & cold treatments, Ultrasound and electrotherapy are proven methods to speed recovery. The later stages will involve physical therapy to strengthen the thigh muscles and restore full ROM and elasticity of the damaged tissues. In complete tears, the torn anterior cruciate ligament cannot be sewn back together and therefore the ligament must be reconstructed during surgery by taking ligaments or tendons from another part of the leg and connecting them to the tibia and femur. To provide stability an elastic bandage, or a brace, around the knee can keep the swelling from getting worse and provide additional stability and compression. An unstable knee may lead to injuries of the meniscus and arthritis.

When can one return to sport or activity? One may safely return to sport or activity when the knee and leg have regained normal strength, elasticity and ROM compared to the uninjured knee and leg, there is no pain, the effusion has gone.

How can ACL sprain be prevented? Unfortunately, most injuries to the ACL occur during accidents that are not preventable. However, one may be able to avoid these injuries by having strong thigh and hamstring muscles and maintaining a good leg stretching routine.