First, a few things you need to know about the lesser know posterior cruciate ligament. The PCL runs from back to front opposite the ACL which runs from front to back, as can be seen in the MRI representation below. The PCL is responsible for the stability of backward motion at the knee joint. A key feature regarding the PCL is it does not play a significant role in side to side stability or rotational stability. Now let's dive into our usual breakdown of the injury.
Mechanism of Injury
Typically occurs as a direct contact to the front of the lower leg, when the knee is in a 90 degree bent position. The classic non-sports scenario is when the knee strikes the dashboard in a car accident. However, sports-related injuries usually occur with a direct fall on the knee or a direct impact to the front of the lower leg. When a complete tear occurs, the athlete may also report a "pop" just as when an ACL is torn.
Exam & Evaluation
Athletes will typically have swelling and fluid over the entire knee, not just the inner aspect or outer aspect. The swelling can be described as "like a water balloon" or "like a grapefruit" and should be apparent within the first 24 hours of the injury. On examination, a Posterior Drawer Test can be performed to check the stability of the PCL ligament. Basically the lower leg is pushed backwards at the knee to see if there is laxity present (see below). One must be careful on examination, in that a torn ACL may give the appearance of a falsely positive posterior drawer test. Many times a PCL tear is associated with other injuries, such as a meniscus tear or lateral collateral ligament tear. Although the diagnosis can be suspected on physical exam, an MRI is generally accepted as the appropriate test to confirm the presence of an PCL tear. It is important to determine if other structures are damaged, which could impact the stability of the knee and the treatment course.
Posterior Drawer Test
Normal MRI Showing Intact ACL and PCL
Treatment Plan
In general, the recommendation for a partial or complete PCL tear is to non-surgical. However, in cases where a high level athlete has a complete tear with symptomatic instability surgery may be considered. Typically extensive physical therapy and rehabilitation will be needed with non-operative protocols returning 6 to 24 weeks depending upon the extent of tear. Of note, the athlete should limit bending of the knee to 90 degrees while activating their hamstring as this causes the highest stress to the PCL. Additionally, if the PCL is torn in conjunction with other structures leading to rotational instability surgical repair is typically recommended.
Return & Sports Considerations
The research shows that, in general, patients with isolated PCL tears can return to sport with good function. An example study is provided below showing that after 10 years patients remained active, have good strength and range of motion after non-operative treatment of an isolated PCL injury.An athlete should consider a functional assessment, testing such criteria as strength, agility and balance prior to return, even if they have met time criteria for return back to sports. Functional assessments can uncover muscle imbalance, weakness or improper movement patterns that can put an athlete at risk for re-injury.
