Patellar tendon injury

Last night while attempting to cover first base, Angels pitcher Garrett Richards planted his left leg and then went down in a great deal of pain.  The video of the injury can be seen here, around the 1:20 mark.  If you watch closely, you will notice that when he plants his left leg, his knee is in an extreme amount of flexion (when the knee bends).  The increased amount of range of motion likely led to the significant tear or rupture of his patellar tendon.

The patellar tendon is located on the anterior (front) side of the knee.  It runs from the patella down to the tibial tuberosity, which is the bump on the anterior side of the tibia.  It's transmits force from the quadriceps to the tibia, causing the knee to extend (straighten).  Most muscle/tendon injuries occur when the structure is placed under a great deal of tension, which occurs when the muscle/tendon is being lengthened and loaded. Imagine taking a rubber band and stretching it.  As you stretch it more and more, it starts to develop small tears, and if you keep stretching it, it will eventually rupture.  Muscles and tendons behave very similarly when loaded under tension (stretching).  As the knee moves further and further into flexion, the patellar tendon continues to lengthen, and it some level of stress (or load), the tendon will start to tear and eventually rupture.  The amount of tension the patellar tendon can sustain is different for every person, but if you watch the video, you can see that his knee goes into an extreme amount of flexion in a very short period of time, which indicates a very high rate of loading.  If the patellar tendon is completely torn, it will have to be repaired surgically, and the recovery/rehab time is close to a year.  It's a devastating injury for one of the best pitcher's for the team that currently has the best record in baseball.

Paul George Injury

Paul George, while playing in an exhibition game for Team USA last Friday, suffered a fracture of both his tibia and fibula.  I'm not going to post a picture of the injury or the video, because it was a horrific injury, but you can find it on the internet.  George has been playing basketball his whole life, landed thousands of times, and never had anything like this happen.  In fact, almost all basketball players jump and land thousands of times throughout their careers and never sustain an injury like this.  Many players do sprain their ankles when landing, and occasionally tear an ACL (see Derrick Rose), but this type of injury is very rare.  Kevin Ware from Louisville suffered a similar injury during last season's NCAA tournament.  So what went wrong this time for George?

As you can see in the picture above, George lands with his right leg at approximately a 45 degree angle in relationship to the ground.  He actually hits the base of the goal with his foot before hitting the ground.  Newton's 3rd law of motion tells us that for every action there is an equal and opposite reaction.  Most of the time when basketball players jump, they land with their feet directly under their center of mass, and the force from the ground (ground reaction force) is transmitted straight up the leg without much of a problem. In George's case, because he is landing at this angle and his foot is a large distance from his center of mass, the ground reaction force creates a bending moment around the middle section of both the tibia and fibula, causing them to fracture.  Many times when these fractures occur, it's not because of the magnitude of the force, but more about the angle of force application and its relationship to the person's center of mass. George has a long road ahead but I am sure he was operated on by the best orthopedic surgeons and will receive the best therapy possible.