Cross your knees

There are two cruciate ligaments in the knee. They are both attached to the tibia (shin bone) and femur (thigh bone) and criss-cross in the knee; they are named from the point at which they attach to the tibia (anterior cruciate on the front part, posterior cruciate on the back part). The anterior ligament keeps the tibia from sliding too far forward on the femur. The posterior ligament keeps the tibia from sliding too far back on the femur. The posterior cruciate ligament is actually a stronger ligament than the ACL.

Injuries to the posterior cruciate ligament (PCL) are more common in sports than appreciated. They may constitute 20% of all knee ligament injuries but are often not diagnosed. A surprising number of high-level athletes compete even with a complete PCL tear. Although injuries to the anterior cruciate ligament (ACL) are more commonly diagnosed and usually require surgical treatment, PCL injuries are equally important to diagnose because they often respond to conservative treatment. If not properly managed, long-term consequences are knee instability or arthritis.

The usual mechanism of injury is a force delivered to the front of the shin, driving the shin backwards, and overloading and tearing the ligament. In sports, blows or falls onto the flexed knee are the common mechanism. It is obvious derby is a sport where falls onto the knee are frequent and forceful. This force may be increased by a knee pad that has slipped down. Sometimes, forceful hyper-extension of the knee with the foot planted causes the injury.

The symptoms are similar to that of an ACL injury but more subtle in many cases. In fact, many people have old PCL tears that don’t cause enough symptoms to be easily noticed. Sudden onset of pain, more often in the back of the knee, with swelling and decreased range of motion of the knee are common. During the injury, an audible or palpable “pop” may be heard, although this is not as common as in ACL injuries. The knee will feel unstable but not as much so as with ACL tear or a PCL tear combined with other ligament injuries. More often, the knee described as “not reliable” or feels “unsteady.”

There are three grades of injury. Grade I is a partial tear. Grade II is a complete tear of the PCL only. Grade III is a complete tear of the PCL with other associated ligament or knee structure injuries.

The diagnosis starts with an exam by your medical team since the physical exam can often confirm the PCL tear and give clues to other ligament injuries. An x-ray may be needed to rule out a fracture. If there are other suspected injuries or the diagnosis is not clear, MRI will help.

In grades I - II, treatment will generally be conservative (i.e., no surgery). After initial RICE and immobilization to relieve pain, the goal will be to support the injured ligament by strengthening the quads and core muscles and with a knee brace. Many athletes can return to their sport with this kind of treatment in 6 - 8 weeks. If you don't have an athletic trainer to advise you, here are several sources for core and quads muscles exercises:

http://orthoinfo.aaos.org/topic.cfm?topic=A00564
http://physicaltherapy.about.com/od/strengtheningexercises/ss/QuadStrength.htm
http://www.mayoclinic.com/health/core-strength/SM00047.

With some grade II injuries (associated with a fracture or very unstable knee) and grade III injuries, surgery is likely required to repair the ligament. It is a difficult surgery so it should be done by a well-trained orthopedic surgeon.

The best method of prevention is to avoid direct falls onto the knee - not easy in derby - but if you can fall slightly to the side and slide, it may help. Wearing well-fitted knee pads is also recommended. There has been discussion about using a knee pad that extends down the shin or using shin guards and knee pads, but there is no evidence to confirm the value at this time.

Save your knees, you need them to bounce children on!