The Arizona Cardinals appear to have suffered a significant blow in their preseason game Friday night against the Green Bay Packers. Rookie running back Ryan Williams was taken off the field in the third quarter of the Cardinals 28-20 loss to the Green Bay Packers.

Williams, a second-round draft pick in this year’s NFL draft, was set to be the Cardinals’ backup at running back behind Beanie Wells. He was reportedly taken off the field after one of the Packers players landed on Williams’ leg. Much of the team was seen consoling the former Virginia Tech star after the injury. Head coach Ken Whisenhunt told the media after the game that the team suspects Williams ruptured his patellar tendon.

If the presumed diagnosis turns out to be true, it would be a big loss. The patellar tendon is the tendon that connects the patella (kneecap) to the tibia (shin bone) below it. It is part of the extensor mechanism that helps to extend the knee. If it is ruptured, an athlete cannot extend his knee or lift it up on his or her own. A torn patellar tendon does not typically heal, and therefore sports medicine physicians almost always repair these injuries surgically.

The team likely will ask the team doctors to obtain an MRI on Williams’ knee, although it is usually a diagnosis that can be made by physical exam. Usually doctors can feel a defect where the patellar tendon should be attached, and the player will be unable to lift his leg. The MRI would just confirm the diagnosis and check for other injured structures.

If torn, surgery to repair the patellar tendon would take place in the next few days. Surgery involves making a small incision and reattaching it through drill holes in the patella. Surgery is a short outpatient procedure, but the rehab is a long process. The surgeon has to slowly allow the athlete to regain knee motion in a way that doesn’t risk disrupting the repair. Once Williams has full knee motion, he will work on regaining full strength and then functional activities. In all, it will likely be 3-4 months before Williams is allowed to do much athletic activity, so his season almost certainly would be over. Fortunately, if surgery goes well and he regains full motion and strength, he likely will have complete recovery and a great chance to get back to football.