Knee

• ACL – prevents the tibia from moving forward
• PCL – prevents the tibia from moving backward
• MCL – resists a knock-knee force
• LCL/PLC – resists a bow-legged and external rotation (turning outward) force

All the ligaments also prevent different and varying degrees of rotation through the knee.

The most common ligament injured is the ACL, followed closely by the MCL. These are usually injured during sporting activities, and usually occur after contact or a twisting/pivoting motion without contact. PCL and LCL/PLC injuries usually occur after higher energy injuries such as high-speed collisions or motor vehicle accidents. These ligaments can also be sprained (partially torn), and treatment will depend on the degree of instability symptoms experienced by the patient.

The most common symptom upon injury is the feeling of a pop in the knee; you or others around can sometimes hear this. The knee will often (but not always) swell on the day of injury and be quite painful to move. The swelling usually decreases over the first week as your motion improves, and most people are able to go on with day-to-day activities at this time. You may note the sensation of instability in the knee and occasional (or frequent) “giving out” during simple movements like sitting and standing, walking, or turning. Knees with multiple structures injured will usually have significantly more instability symptoms. In severe cases the knee can dislocate upon injury – this is an emergency and should be evaluated immediately by emergency medical personell.

This depends on what ligaments are torn and the timing of surgery. Injuries to the ACL and PCL require reconstruction – replacement of the torn tendon with a new tendon or ligament graft. This graft can come from the patient (autograft) or from a tissue bank (allograft). The ACL and PCL make up the “central pivot;” these two ligaments are on the inside of the joint and centered between the femur and tibia. Because of the central location within the joint, ACL and PCL injuries are usually reconstructed arthroscopically through a few small incisions. MCL injuries very rarely need surgical treatment; most will heal over the course of 6-12 weeks with protection in a knee brace, depending on the severity of the tear. Injuries to the LCL/PLC complex usually occur in addition to ACL or PCL tears. We typically try to repair these ligaments within 2-3 weeks of injury. If the injury is older than this, we often recommend reconstruction of the ligaments with tendon allograft.

Recovery after an ACL reconstruction is generally a 6-9 month recovery before beginning sporting activities. You are able to walk on the limb with crutches beginning the day of surgery, and therapy to regain motion begins immediately. Strengthening starts by 6 weeks, and light jogging and regaining power begins at 12 weeks. If additional ligaments require treatment, or if you have a meniscus repair, the recovery period slows down depending on exactly what was repaired and reconstructed.

In addition to the symptoms mentioned above, a physical examination by a medical professional comfortable with evaluating and diagnosing knee injuries is extremely important. Plain xrays of both knees, as well as an MRI assist in completing the diagnosis and identifying any associated injuries.

Not everyone with an ACL tear needs a reconstruction. There are many patients who are able to regain their motion and strength in the limb and don’t have significant symptoms of functional instability. Patients that we suggest have their ACL reconstructed regardless of instability symptoms are pediatric patients and young adults. The reason for this is to try and prevent repeated and more severe instability episodes that can lead to cartilage and meniscus injuries. If you have torn your ACL (or another ligament in your knee) and have repeated episodes of instability and looseness of the knee that prevent normal daily activity and maintenance of an active lifestyle, you will likely benefit from a reconstructive procedure.