The most common athletic injuries to the knees involve which part of the knees?

Many: The knee is commonly injured because it is a weight bearing, planting and pivoting joint subject to many forces. The most common is the leg planted and the knees goes inward stressing the inside of the knee. You can do anything from spraining the mcl, tearing the meniscus to tearing the acl. A "pop", pain and immediate swelling usually signifies a significant injury. Ice, wrap, elevate-see doctor.

Depends: Different injuries are more common depending the age and sex of the athlete and the sport one is participating. Generally speaking the most common athletic knee injuries occur to the ligaments and meniscal cartilages. Injuries to the articular cartilage, fractures, contusions and tendon injuries also occur.