Knee Sprain

Presentation

After twisting the knee during a fall or sports injury, the patient complains of knee pain, possible swelling, and variable ability to bear weight. There may be a joint effusion or spasm of the quadriceps, forcing the patient to hold the knee at 10 to 20 degrees of flexion. See Fig. 113.1 for normal anatomy.

With an anterior cruciate ligament (ACL) tear, there will most likely be a noncontact injury involving a sudden deceleration (landing from a jump, cutting, or sidestepping), hyperextension, or twisting, as is common in basketball, football, and soccer. This may be accompanied by the sensation of a “pop,” immediately followed by significant nonlocalizing pain and rapid development of swelling and effusion. Significant injuries will have a positive Lachman test on examination.

The medial collateral ligament (MCL) is another frequently injured knee ligament. This may be torn with a direct blow to the lateral aspect of a partially flexed knee, such as being tackled from the side in football, or by an external rotational force on the tibia, which can occur in snow skiing when the tip of the skin is forced out laterally. There may also be an awareness of a “pop” during the injury, but unlike the ACL tear, it is localized to the medial knee, along with more focal pain and swelling. Significant injuries cause laxity of the MCL with valgus stress testing at 30 degrees of flexion.

The medial or lateral meniscus can be torn acutely with a sudden twisting injury of the knee while the knee is partially flexed, such as may occur when a runner suddenly changes direction or when the foot is firmly planted, the tibia is rotated, and the knee is forcefully extended, as when a football lineman turns and springs up at the beginning of a play. Pain along the joint line is felt immediately, and there is often a mild effusion with tenderness to palpation along the corresponding medial or lateral joint line. There may be a positive McMurray test.

Posterior cruciate ligament (PCL) injuries occur with forced hyperflexion, as can occur in high-contact sports, such as football and rugby. Tears of the PCL can also occur with a posterior blow to the proximal tibia of a flexed knee, as occurs with dashboard injuries to the knee during motor vehicle collisions. Hyperextension, most often with an associated varus or valgus force, can also cause PCL injury. There is no report of a tear or pop, only vague symptoms, such as unsteadiness or discomfort. There is commonly a mild to moderate knee effusion, and a significant injury will have a positive posterior drawer test, and a posterior sag sign will be present ( Fig. 113.2 ).

Injury of the lateral collateral ligament (LCL) is much less common than injury of the MCL. This usually results from varus stress to the knee, as occurs when a runner plants the foot and then turns toward the ipsilateral knee or when there is a direct blow to the anteromedial knee. The patient reports acute onset of lateral knee pain that requires prompt cessation of activity.