Inside Slant: Knee injuries on rise overall

We've done our best to track the increase in ACL injuries this season, most recently noting that the majority have occurred on grass. Our friends at ESPN Stats & Information expanded the research this week to include all knee injuries -- tendons, other ligaments, knee caps, etc. -- that have resulted in a player being placed on injured reserve.

The study produced larger numbers, of course, but supported the same basic conclusion: Knee injuries have increased in 2013 relative to this point over the past two seasons. I don't know that we're any closer to understanding the reason -- the data doesn't reflect the popular opinion blaming rules that encourage low hits -- but we will continue tracking nonetheless.

The chart is updated through Monday night's game. Among other things, it shows that knee injuries have sent more players to the IR than all of the 2011 season, based on ESPN research. The NFL would exceed its 2012 mark if 12 more players suffer the same fate over the next three weeks' worth of games.

As we've pointed out a few times, there is no golden metric for injuries. IR accounts only for the most serious of injuries, and sometimes players are waived off IR once their injury settlements expire. After the season, the NFL's competition committee will compile a collection of data that includes IR numbers, missed starts, missed practice time and other metrics to form an overall picture of the league's health situation.

The issue is in the news this week, and has been for much of the season, because of several high-profile injuries caused by intentionally low hits. The most recent victim is New England Patriots tight end Rob Gronkowski, who tore two knee ligaments last Sunday because of a low hit from Cleveland Browns safety T.J. Ward.

Ward mirrored comments made in August by Houston Texans safety D.J. Swearinger, whose low hit on Miami Dolphins tight end Dustin Keller resulted in a traumatic knee injury. Both safeties said that stiff penalties and fines for hits to the head and neck area left them no choice but to tackle low.

Green Bay Packers receiver Randall Cobb was injured on a similar hit by Baltimore Ravens safety Matt Elam, but the resulting broken leg isn't part of this study. Regardless, a review of the full list provided by ESPN Stats & Information doesn't reveal many more instances.

Several alternative theories have floated this season. Commissioner Roger Goodell said at a fan forum in London that some players might be choosing shoes that emphasize speed but sacrifice stability and thus protection from knee injuries. Meanwhile, Dr. Mark Adickes -- a former NFL player who is now an orthopedic surgeon -- said last month that reduced football training time in the spring and summer could make players more susceptible to ACL injuries.

We'll monitor these numbers during the next three weeks and into the offseason.