A valgus knee injury is a common football injury. It occurs when the knee is forcibly bent inward.
Injuries can be as mild as an MCL sprain. (stretching or partial tearing of the inner ligament of the knee) If strong enough, the inside meniscus can tear as well as they are firmly attached to each other.
If the force is even stronger, it can crack the outside shin bone resulting in a tibial plateau fracture like in the case of Saints coach, Sean Payton.