ACL - ANTERIOR CRUCIATE LIGAMENT 

source: Steadman-Hawkins

 Overview

• Origin: top surface of the tibia
• Insertion: The large notch at the end of the femur.

• Function: Prevents the tibia from sliding too far forward underneath the femur. It also helps prevent over-straightening and over-rotation of the femur on the tibia.

An ACL injury usually occurs when the knee is sharply twisted or extended beyond its normal range of motion. 

• Grade I - Sprain - Relatively minor. Fibers are stretched.
• Grade II - Partial Tear - More severe. Fibers are torn.
• Grade III - Complete Tear - Most severe. Fibers completely torn.

• Basketball, Skiing and Football require movements that cause the femur to pivot on the tibia.
• Skiing: Ski length adds more force to the twisting motion. Stiffness and height of the ski boot cause the forces to be transferred up the leg to the vulnerable knee joint.
• In Contact Sports the ACL can be damaged along with the medial collateral ligament (MCL) when the knee is struck from the outside. Also, a hit that results in the tibia being driven forward, the femur being driven backward, or the knee joint being severely hyperextended may result in damage to the ACL.

Competitive female soccer and basketball players have 3-5 times higher risk of ACL injury than their male counterparts. Why?

• Size & strength: The ACL and the notch on the femur that it sits in are smaller in women. The male's lower of body fat and greater muscle mass give the male an advantage in protecting the ACL.
• Mechanics: a woman's pelvis creates a larger angle from hip to knee (Q-angle), may make the knee more prone to injury.
• Neuromuscular: differences in the timing of muscle activation and how women perform risky movements may increase the female's vulnerability to ACL injury. Women tend to change direction and land from jumps in a more erect stance, and this can put the ACL under strain.
• Hormonal differences: focus on estrogen in the female body and its effect on ligament laxity and knee looseness. Although these theories have not been proven, agility training and muscle strengthening seem to be appropriate measures women can take to help prevent injury.

• "Pop" - Many patients, but not all, will hear or feel a "pop" when the ACL tears.
• Immediate onset of swelling - An indication that there is bleeding from the injured ligament.
• Pain - Most patients experience quite a bit of pain with an ACL injury.
• Instability - Patients often describe a buckling or unstable sensation in the knee.

• The Lachman Test, Anterior Drawer Test, and Pivot Shift Test are exams the doctor may use to see how much the tibia moves in relation to the femur. Pain, swelling, and muscle spasms in the early stages of an injury may make it difficult for the doctor to diagnose the degree of instability with manual tests.
• An arthrometer, a machine that measures joint looseness in the knee, may be used.
• X-rays can reveal signs of bone fractures, chips, or arthritis.
• Since X-rays can only show bone, a Magnetic Resonance Image (MRI) may be ordered to assess damage to soft tissue such as ligaments, tendons, and cartilage. 
• If further testing is needed to clearly evaluate the problem, an arthroscopy may be recommended. During an arthroscopy, a tiny fiberoptic scope is inserted into the joint. The doctor uses this scope to visually assess the damage. In most cases, a diagnosis can be made without using this surgical procedure.

• Strength - The muscles surrounding the knee, particularly the hamstring muscles, must be strengthened. These muscles can then take on some of the ACL's job of stabilizing the knee joint.

• Proprioception - Proprioceptive nerves in the ligament send info to the brain about where the body is in space. The brain then sends the info to the muscles to tell them how to move the joint. Damaged nerves in the ligament must be retrained so that the muscles move the joint properly.

• An ACL brace will usually be prescribed to stabilize the knee and to prevent re-injury. Most braces have a rigid frame. A trained specialist will fit the patient with the brace since a good fit is essential. 

• A continuous passive motion (CPM) machine is used in the recovery room and the first night. This machine gently and steadily bends and straightens the patient's knee.

• Crutches are used for the first 7 -10 days after surgery for comfort. 

• Bike without resistance and pool exercises to increase motion begin at 2 weeks post-surgery.

• A sports cord (an elastic resistance strengthening tool) and the treadmill are initially used.

• Stair-stepper or elliptical trainer is added at about 8 weeks.

• Strengthening using weights is allowed at 8 - 12 weeks

• Running is allowed at 3 months
• Pivoting and twisting activities can begin at 4 to 5 months.

• This phase usually occurs approximately 6 months after reconstructive surgery.

 Operative Recovery

Knee Braces

• Surgeons may use braces only during the rehab phase or recommend that patients always use a brace.
• A post-operative brace is often immediately after surgery. This is a sturdy, adjustable brace that limits motion and gives protection from a fall or twist.
• A lighter brace is often used during later stages of rehab and during sport activity.

• Exams show that 90 to 95% of patients with ACL reconstructions have good to excellent results. 

• Motion and Stability / Symptoms such as pain or swelling

• How well the knee functions in daily living and whether the patient has returned to sports

• Failure of the graft, re-injury to the ACL, or injury to other structures in the knee are possible, and can cause instability.
• Blood clots and infection in the joint are very rare occurrences.

• Some knee ligaments, such as the medial collateral ligament (MCL), heal reliably without surgery.
• Some partially torn ACLs, particularly in children and adolescents, may also heal without surgery.
• However, a complete tear of the ACL rarely heals. This is probably due to the amount of energy involved in the injury, the lack of blood supply, and the interior location of the ACL. The torn ACL may scar back to the intact PCL within the knee, but this rarely returns stability to the knee. In fact, even when the ends of a torn ligament are sutured together (called a primary or direct repair), the ligament does not reliably heal. Therefore, surgery for a complete ACL tear (an ACL reconstruction) involves replacing the ACL with other tissue (a graft).

• Surgery is not required for all ACL injuries.
• Partial tears, in which a physical examination shows a relatively stable knee, may be treated with bracing and rehabilitation.
• Even some patients with complete ACL tears do not need reconstruction.These "copers" are typically older patients with lower physical activity, who do not participate in pivoting and cutting activities.

• One reason to reconstruct the ACL is to provide knee stability that allows for return to activities and sports.
• Another reason is to provide knee stability in order to prevent more injury, such as a meniscal tear, which may eventually lead to degenerative joint disease.

• An MRI is not always required to diagnose an ACL tear.
• An ACL tear can be accurately diagnosed with a physical examination.
• However, when the knee is very swollen and painful, an accurate examination can be difficult.
• Also, an MRI can be useful to reveal other associated injuries.

• There are advantages and disadvantages to the many technical aspects of an ACL reconstruction including the type of graft, methods of securing the graft, and rehabilitation protocols.
• There is no clear consensus as to which graft is best. In the end, the surgeon's experience with the chosen technique and the patient's commitment to the rehabilitation program are probably more important factors in a functional outcome.

• Rehabilitation programs after ACL reconstruction are constantly evolving, shortening the return to sports.
• Most patients can start to return to their sports about 6 months after reconstruction.