The Anterior Cruciate Ligament (ACL) is one of two crossing ligaments, along with the Posterior Cruciate Ligament (PCL) , found inside the knee which connect the femur (thighbone) and the tibia (shinbone) . These cruciate ligaments control back and forth movement of the lower leg and act to hold the bones together as well as stabilise the whole knee. Ligament injuries are considered "sprains" and can be graded by severity; grade 1 sprains - the ligament has been slightly stretched and becomes mildly damaged but can still keep the knee joint stable, grade 2 sprains (sometimes referred to as a partial tear) - the ligament is stretched until it becomes loose, and grade 3 sprains (often referred to as a complete tear ) - the ligament has been stretched until it splits into two pieces. The ACL can be injured in multiple ways, usually through sudden powerful movements which put too much stress on the knee. These include changing direction rapidly, stopping suddenly, slowing down while running, landing from a jump incorrectly, and direct contact or collision on the knee which can overextend the lower leg . These injuries can be prevented by strengthening of the leg muscles which support the load of the ligaments, strengthening of the core muscles, and training for correct technique in movements that place stress on the knee. Before treatment is discussed, a physical exam is used to assess for swelling and tenderness as well as the range of motion and overall function of the knee. Further techniques such as X-rays, to check for a bone fracture, and MRI or Ultrasound scans, to check for signs of damage in the tissues of the knee, are used to clarify the severity and location of the damage. Treatment for ACL injuries depends on the severity . Slight sprains or partial tears can be treated conservatively with rest, ice application, compression, and elevation (as known as the RICE steps ) as well as potentially a brace and physiotherapy to strengthen the supporting leg and core muscles. Complete tear treatment depends on the patient; if they are elderly or have a very low activity level then surgery may not be needed and the previous treatments can be used. However, if the patient wants to return to sports or activities that involve movements particularly stressful to the knee, such as basketball, football or rugby, then surgery is the only option remaining .
