Curriculum · Musculoskeletal / Orthopedic / Rheumatology
Knee ligament injury
What it is
The knee is held by two cruciate ligaments, and either can tear when the joint is injured. An anterior cruciate ligament (ACL) tear happens when the feet stay planted and the upper torso rotates, as when another player collides with a leg that cannot turn with the body. A posterior cruciate ligament (PCL) tear follows a hyperextension injury of the knee. Getting the diagnosis right matters: accurate testing can lead to appropriate referral and treatment for ACL tears, and early detection can lead to better outcomes. The collateral ligaments sit beside the cruciates. The medial collateral is the most commonly injured knee ligament and the lateral collateral the least commonly injured; the tear is seen after a direct blow to the lateral knee, and commonly an ACL or PCL injury goes with it. The posterior cruciate tear is also seen during falls on a flexed knee and in dashboard injuries in motor vehicle accidents.
How it presents
Pain is immediate and severe enough that the injured player is unable to continue the game. Swelling follows, and examination may show a mild knee effusion with painful end ROM. On a knee that has lost one of its cruciate ligaments, the tests below become positive. The anterior cruciate tear presents with a pop in the knee, and the patient may also complain of knee instability or giving way.