What is a slipping knee? I read on-line that my favorite football player has this type of injury.
Slipping knee most likely refers to an unstable knee from injury of important ligaments or other soft tissues. For example, without the anterior cruciate ligament (ACL) to hold the lower leg stable, the tibia (lower leg bone) slips forward underneath the femur (thigh bone).
If it's a severe enough injury, the person may feel a definite clunk as the bone shifts (subluxes). This type of injury is actually diagnosed by using clinical tests that reproduce this clunk. The two most commonly used tests are the Lachman test and the pivot-shift test.
The orthopedic surgeon or sports medicine specialist is able to grade the severity of the injury using these tests. That directs treatment. With athletes, the ability to jump, stop quickly, change direction (pivot and shift) is critical and must be restored.
Moderate-to-severe injuries (higher grades) may require surgery to reconstruct the knee. Milder injuries (lower grade) may respond to conservative (nonoperative care) with rest, activity modification, and antiinflammatory medications. Physical therapy to restore normal motion and strength is an important part of the return-to-sport equation.
Clayton G. Lane, MD, et al. The Pivot Shift. In Journal of the American Academy of Orthopaedic Surgeons. December 2008. Vol. 16. No. 12. Pp. 679-688.