Analysis of Season-Ending Knee Injuries in the National Football League 2006-2008
Abstract
Investigation of season-ending knee injuries in the National Football League (NFL) from 2006-2008. Researcher chose to expand my search to include any knee injury that required a player to be placed on Injured Reserve as this information is widely available to collect for the last three years. With these adjusted parameters, it was possible to perform more detailed analysis.
A summary of findings: The rate of season-ending knee injuries is inversely proportional to the number of team wins and the position of running back has the highest season-ending knee injury rate per player. The studies of the injury rate vs. team, division, and month did not produce results with statistical significance.
Introduction
Knee injuries are pervasive in the National Football League; the risk of particular knee injuries may be up to 10 times higher in football than in other sports (Bradley 2001). Because of this fact and, a matter of personal interest to the researcher, and also the desire to analyze data that has not been exhausted by prior studies, the topic of season-ending injuries in the NFL was chosen to study.
Definitions
The following definitions and graphics were collected from Football 101: Knees and Cartilage by Mark Lawrence.
Anterior Cruciate Ligament (ACL): This is the most important ligament in the knee, holding the entire joint together (see Fig. 1). The knee becomes unstable if this ligament is severed and the injury will require invasive surgery to repair. The player will miss several months of playing time.
Medial Collateral Ligament (MCL): This is the ligament that resides on the inside of the knee, preventing it from collapsing inwards (see Fig. 1). It can be injured by a hit to the outside of the knee, pushing it inwards. This is a moderately common injury in football, but since the MCL is not critical to knee stability an athlete may be able to continue playing by wearing a brace.
Lateral Collateral Ligament (LCL): This is a ligament that resides on the outside of the knee, preventing it from collapsing outwards. It is rarely damaged in football.
Posterior Cruciate Ligament (PCL): This is the ligament that prevents the knee from hyper-extending. Serious injuries to this ligament are not common in football. Minor injuries the PCL caused by hyperextensions can be treated with time, a brace, and anti-inflammatory medication.
Kneecap/Patella: This is a bone that allows the patellar tendon to slide easily over the front of the knee and increases leverage (its presence increases the force provided by the quadriceps by 30%).
Patellar Tendon: This is the tendon that attaches the muscles to bones in the knee. If it becomes irritated, it can become a chronic condition and also increase the risk that the tendon can rupture. Tendon rupture is a very serious injury requiring months of rehabilitation.
Cartilage & Meniscus: These white, solid substances create the lubrication system for the knee (see Fig. 2 & 3). Only a small part is alive and able to grow where it has worn away. If the live section is injured, the body will replace it with calcium as a sub-par substitute causing knee pain. If the meniscus has a minor tear, it will require “scoping” treatment where tubes are inserted into the knee to find the rough edge of the meniscus and smooth it over. Rehabilitation normally takes a few weeks. A complete tear of the meniscus requires more invasive surgery and longer recovery time.
Osteoarthritis: This is a condition where the cartilage and meniscus have been damaged to the point that there is bone-to-bone contact in the knee which is extremely painful. No specific treatment exists to halt cartilage degeneration causing this condition.
Methods
Research methods included data mining on major websites such as NFL.com, ESPN.com and Yahoo! Sports and data analysis techniques. The NFL Transactions List provided the most detailed information by listing the players placed on Injured Reserve, team, date, and type of injury. Researcher was able to build a detailed database in MS Excel (see Appendix A for raw data) of season-ending knee injuries from this data and run various data analysis on this list. Various correlation tests were performed on variables selected based on a the small amount of information found in various data collected. The R2 for the correlations were tested that showed some interesting and significant findings. This information can be found in the Discussion section below.
Discussion
The first correlation tested was the comparison of season-ending knee injury rates versus time (See Fig. 5). This plot was generally uninteresting as one would expect the injury rates to be low during the off-season and high during the regular season months. One note would be the large spike between November and December 2007 (13 season-ending knee injuries reported in November and 32 the following month). This could be due to something real or the data may be skewed if players who were injured in November were not placed on IR until December.
The second test was to compare the season-ending knee injury rate by NFL team (see Fig. 6). This analysis was generally uninteresting, except to note that the Dallas Cowboys had only one qualifying injury in the three year reporting period. This may be something to investigate further as to whether the reporting was lax on the part of the Cowboys or NFL administration or if the Cowboys actually have very few serious knee injuries afflicting their players. If that was found to be the case, a study of the Cowboys’ training conditions etc. would be useful for attempting to lower the knee injury rate for other teams.
The third test was to see the correlation between season-ending knee injury rate and the NFL Divisions (See Fig. 7). Not surprisingly, the NFC East had the lowest number of these injuries as the Dallas Cowboys are a member of that division. Therefore, this comparison provided no new information beyond that provided by the comparison by NFL team.
Upon finding in the above comparisons that the Detroit Lions, Oakland Raiders, and Cleveland Browns (all teams with low winning percentage in the last three years) had some of the highest rates of season-ending knee injuries, the researcher decided to run a comparison of the injury rate against cumulative wins 2006-2008 (See Fig. 8). The R2 values for the below curves were .92.
This was quite possibly the most interesting finding: a clear inverse relationship between cumulative team wins and season-ending knee injury rate. The researcher found this particularly interesting because there were no studies or articles found to even suggesting this relationship. Unfortunately this is just a correlation; it cannot prove a causal relationship, but further study should be considered. It is possible that 1) a high season-ending knee injury rate causes teams to lose by taking out key players and bringing a steady stream of backups into the first string, 2) a low winning percentage causes players to be injured due to incompetence on the field, or 3) an entirely different factor causes both effects such as bad management, training, morale, or coaching.
Finally, the last comparison that was investigated was the season-ending knee injury rate versus position (See Fig. 9).
Fig. 9 depicts the highest number of season-ending knee injuries afflicting offensive and defensive linemen. This is expected because the offensive and defensive line positions have the highest average weight of all positions in professional football. The knee is particularly susceptible to injury in the presence of excess weight.
Although useful information is obtained from the raw numbers of injuries depicted in Fig. 9; it must be considered that there are not as many quarterbacks and kickers on the team as wide receivers and linemen. In order to correct for this, the researcher estimated the average number of each position on an NFL roster of 53 and normalized the injury numbers by dividing by those averages. This data can be found in Appendix B and a plot of the normalized injury numbers by position is below:
The normalized data tells a different story than the raw data. After the normalization, it appears as though running backs following by cornerbacks incur the highest number of season-ending knee injuries. This makes sense due to the excessive wear-and-tear to these athletes. Running backs and cornerbacks perform more cutbacks and changes of direction while running than do other players. This causes more stress on the knee joint, therefore the risk of serious injury is higher.
Conclusion
The results from the knee injury by position (regular and normalized) comparisons agree with the following statement from Anterior Cruciate Ligament Injuries in the National Football League: Epidemiology and Current Treatment Trends Among Team Physicians by James P. Bradley: “Offensive and defensive linemen had the most ACL injuries. However, the risk of ACL injury was greatest for running backs.” Bradley’s article is specific to ACL injuries while the researcher analyzed all types of season-ending knee injuries, yet the results are the same. This makes sense because ACL injuries are common in the NFL and the most serious type of knee injury. More research should be conducted in this area to gather more data and expand on these findings. The researcher also suggests running comparisons for knee injury rate versus age, race, and Body Mass Index. The injury rate by position suggested that differences in physiology such as body weight could be a factor in the rate of season-ending knee injuries.
Appendix A: Raw Data
49ers 11-Aug-08 Damane Duckett T KNEE
49ers 16-Oct-08 Shawntae Spencer CB KNEE
Bears 26-Aug-08 T.J. Rushing CB KNEE
Bengals 31-Aug-08 Jonathan Lewis DT KNEE
Bengals 3-Sep-08 Jeremi Johnson RB KNEE
Bengals 27-Oct-08 Corey Lynch S KNEE
Bills 26-Aug-08 Osi Umenyiora DE KNEE
Bills 4-Sep-08 Angelo Crowell LB KNEE
Bills 22-Oct-08 John DiGiorgio LB KNEE
Broncos 26-Jul-08 Edell Shepherd WR KNEE/LEG
Broncos 23-Sep-08 Tom Nalen C KNEE
Broncos 22-Oct-08 Boss Bailey LB KNEE
Broncos 10-Nov-08 Ryan Torain RB KNEE
Browns 22-May-08 Daven Holly CB KNEE
Browns 4-Sep-08 Antwan Peek LB KNEE
Browns 2-Nov-08 Ryan Tucker G KNEE
Buccaneers 29-Jul-08 Torrie Cox CB KNEE
Buccaneers 15-Oct-08 Byron Storer RB ACL
Buccaneers 19-Nov-08 Geno Hayes LB KNEE
Cardinals 8-Aug-08 Scott Peters C KNEE
Cardinals 6-Sep-08 Al Johnson C KNEE
Cardinals 4-Nov-08 Ali Highsmith LB KNEE
Chargers 11-Sep-08 Shawne Merriman LB KNEE
Chiefs 22-Oct-08 Brodie Croyle QB KNEE
Chiefs 29-Oct-08 Jean-Philippe Darche C KNEE
Chiefs 4-Nov-08 Kolby Smith RB KNEE
Colts 12-Aug-08 Michael Coe CB KNEE
Colts 26-Aug-08 Zac Herold TE KNEE
Colts 31-Aug-08 Ryan Lilja G KNEE
Colts 15-Oct-08 Mike Hart RB KNEE
Colts 30-Oct-08 Marlin Jackson CB KNEE
Colts 19-Nov-08 Nick Graham CB KNEE
Dolphins 15-Nov-08 Matt McChesney T KNEE
Eagles 31-Aug-08 Lennie Friedman G KNEE
Giants 31-Aug-08 Digger Bujnoch C KNEE
Jaguars 9-Sep-08 Vince Manuwai G KNEE
Jaguars 25-Sep-08 Scott Starks CB KNEE
Jets 9-Aug-08 Brad Kassell LB KNEE
Jets 29-Oct-08 Jesse Chatman RB KNEE
Lions 29-Jul-08 Reggie Ball WR KNEE
Packers 31-Aug-08 Junius Coston G KNEE
Panthers 25-Aug-08 Jason Carter WR KNEE
Panthers 23-Sep-08 Dan Connor LB KNEE
Panthers 8-Oct-08 Ryne Robinson WR KNEE
Patriots 2-Aug-08 Anthony Clement T KNEE
Patriots 9-Aug-08 Tank Williams S KNEE
Patriots 8-Sep-08 Tom Brady QB ACL
Raiders 25-Aug-08 Oren O’Neal RB KNEE
Raiders 25-Aug-08 John Bowie CB KNEE
Raiders 25-Aug-08 Drew Carter WR KNEE
Raiders 31-Aug-08 Arman Shields WR KNEE
Raiders 10-Sep-08 Paul McQuistan G KNEE
Raiders 6-Oct-08 Seth Wand T KNEE
Raiders 28-Oct-08 Justin Griffith RB KNEE
Ravens 8-Aug-08 Quinn Sypniewski TE KNEE
Ravens 8-Oct-08 Kelly Gregg DT KNEE
Ravens 14-Oct-08 Marshal Yanda G KNEE
Ravens 11-Nov-08 Chris McAlister CB KNEE
Redskins 22-Jul-08 Phillip Daniels DE ACL
Saints 31-Aug-08 Greg Fassitt CB KNEE
Saints 19-Oct-08 Montavious Stanley DT KNEE
Saints 10-Nov-08 Mike McKenzie CB KNEE CAP
Saints 15-Nov-08 Brian Young DT KNEE
Seahawks 9-May-08 Wale Dada CB KNEE
Seahawks 31-Aug-08 Chris Cooper DE KNEE
Seahawks 8-Sep-08 Nate Burelson WR KNEE
Seahawks 17-Sep-08 Logan Payne WR KNEE
Steelers 2-Jan-08 Max Starks T KNEE
Steelers 30-Jul-08 Daniel Sepulveda P ACL
Steelers 28-Oct-08 Greg Warren C KNEE
Texans 4-Aug-08 Jimmy Williams CB KNEE
Vikings 11-Aug-08 Jayme Mitchell DE KNEE
Vikings 11-Aug-08 Heath Farwell LB KNEE
49ers 2-Sep-07 Joe Cohen DT KNEE
49ers 3-Sep-07 C.J. Brewer WR KNEE
49ers 21-Sep-07 Manny Lawson LB KNEE
49ers 18-Dec-07 Dominique Zeigler WR KNEE
Bears 13-Jun-07 J.D. Runnels RB KNEE
Bears 2-Sep-07 Daniel Bazuin DE KNEE
Bears 10-Sep-07 Mike Brown S ACL
Bears 10-Sep-07 Dusty Dvoracek DT ACL
Bears 24-Dec-07 Mark Anderson DE KNEE
Bengals 10-Aug-07 Kenny Irons RB KNEE
Bengals 16-Oct-07 Ethan Kilmer S KNEE
Bengals 27-Nov-07 Herana-Daze Jones S KNEE
Bills 11-Oct-07 Kevin Harrison LB KNEE
Bills 28-Dec-07 Copeland Bryan DE KNEE
Broncos 17-Aug-07 Carlos Hall DE KNEE
Broncos 18-Dec-07 Nick Ferguson S KNEE
Browns 2-Sep-07 Mason Unck LB KNEE
Browns 23-Oct-07 Gary Baxter CB PATELLAR TENDON
Browns 31-Oct-07 Ted Washington DT KNEE
Browns 5-Dec-07 Kris Griffin LB KNEE
Browns 24-Dec-07 Ethan Kelley DT KNEE
Browns 24-Dec-07 Mike Adams S KNEE
Buccaneers 26-Jul-07 Charles Bennett DE KNEE
Buccaneers 20-Aug-07 Antoine Cash LB KNEE
Buccaneers 1-Oct-07 Luke Pettigout T KNEE
Buccaneers 1-Oct-07 Carnell Williams RB KNEE
Buccaneers 24-Oct-07 Mark Jones WR KNEE
Buccaneers 31-Oct-07 Torrie Cox CB KNEE
Chargers 27-Aug-07 Tyronne Gross RB KNEE
Chiefs 30-Oct-07 Johnny Baldwin LB KNEE
Chiefs 5-Dec-07 Rudy Niswanger C KNEE
Chiefs 6-Dec-07 Tyler Thigpen QB KNEE
Chiefs 14-Dec-07 Pat Thomas LB KNEE
Chiefs 26-Dec-07 Tyron Brackenridge CB KNEE
Colts 4-Aug-07 Mike Seidman TE KNEE
Colts 9-Aug-07 Anthony McFarland DT PATELLAR TENDON
Colts 4-Oct-07 Rob Morris LB KNEE
Dolphins 24-Oct-07 Renaldo Hill S KNEE
Dolphins 24-Oct-07 Ronnie Brown RB KNEE
Dolphins 7-Nov-07 Abraham Wright LB KNEE
Dolphins 14-Nov-07 Travares Tillman S KNEE
Dolphins 4-Dec-07 Cameron Worrell S KNEE
Dolphins 22-Dec-07 Channing Crowder LB KNEE
Dolphins 26-Dec-07 Andre Goodman CB KNEE
Eagles 2-Sep-07 Ian Scott DT KNEE
Falcons 26-Jul-07 Brian Finneran WR KNEE
Falcons 21-Aug-07 D.J. Shockley QB KNEE
Falcons 23-Aug-07 Jamin Elliott WR KNEE
Falcons 28-Aug-07 Omare Lowe S KNEE
Falcons 9-Oct-07 Wayne Gandy T KNEE
Falcons 23-Oct-07 Reardo Foster G KNEE
Falcons 20-Nov-07 Trey Lewis DT KNEE
Falcons 29-Nov-07 Todd Weiner T KNEE
Falcons 26-Dec-07 Terrance Pennington T KNEE
Giants 15-Aug-07 Darcy Johnson TE ACL
Giants 27-Aug-07 Marcus Bell DT KNEE
Giants 18-Sep-07 Adrian Awasom DE KNEE
Giants 2-Oct-07 Robert Douglas RB KNEE
Giants 31-Dec-07 Craig Dahl S ACL
Jaguars 2-Aug-07 Chris Roberson CB KNEE
Jaguars 2-Sep-07 Mike Walker WR KNEE
Jaguars 26-Nov-07 George Wrightster TE KNEE
Jets 12-Sep-07 Chansi Stuckey WR KNEE
Jets 18-Sep-07 Justin Miller CB KNEE
Jets 27-Oct-07 Jonathan Vilma LB KNEE
Jets 20-Nov-07 Stacy Tutt RB KNEE
Lions 3-Aug-07 Drew Stanton QB KNEE
Lions 17-Aug-07 Alan Ricard RB KNEE
Lions 17-Aug-07 Etric Pruitt S KNEE
Lions 28-Aug-07 Ike Charlton CB KNEE
Lions 28-Aug-07 Daniel Bullocks S KNEE
Lions 2-Sep-07 Frank Davis G KNEE
Lions 4-Oct-07 rian Calhoun RB KNEE
Lions 19-Nov-07 Idrees Bashir S KNEE
Lions 28-Nov-07 Stanley Wilson CB KNEE
Lions 19-Dec-07 Roy Williams WR KNEE
Packers 1-Sep-07 Abdul Hodge LB KNEE
Packers 2-Sep-07 Noah Herron RB KNEE
Packers 15-Sep-07 Carlyle Holiday WR KNEE
Panthers 7-Aug-07 Terrence Melton LB KNEE
Panthers 2-Sep-07 Stephen Williams DT KNEE
Panthers 19-Sep-07 Nate Salley S KNEE
Panthers 30-Oct-07 Curtis Deloatch CB KNEE
Panthers 21-Dec-07 Keary Colbert WR KNEE
Panthers 24-Dec-07 Justin Hartwig C MCL
Panthers 26-Dec-07 Julius Peppers DE KNEE
Patriots 30-Jul-07 Chad Scott QB KNEE
Patriots 2-Sep-07 Oscar Lua LB KNEE
Raiders 6-Aug-07 Isaiah Kacyvenski LB KNEE
Raiders 8-Aug-07 Fred Wakefield TE KNEE
Raiders 31-Oct-07 Tommy Kelly DT KNEE
Raiders 15-Dec-07 Jarrod Cooper S KNEE
Raiders 19-Dec-07 Jake Grove C KNEE
Raiders 26-Dec-07 Justin Fargas RB KNEE
Rams 26-Sep-07 Mark Setterstrom G KNEE
Rams 6-Oct-07 Adam Goldberg T MCL
Rams 17-Oct-07 Raonall Smith LB KNEE
Rams 14-Nov-07 Richie Incognito G KNEE
Rams 27-Nov-07 Pisa Tinoisamoa LB KNEE
Ravens 27-Aug-07 Steve Edwards T KNEE
Ravens 12-Sep-07 B.J. Sams CB KNEE
Ravens 12-Dec-07 Chris McAlister CB KNEE
Redskins 8-May-07 Steven Harris WR KNEE
Redskins 15-May-07 Nehemiah Broughton RB KNEE
Redskins 21-Aug-07 Mike Espy WR KNEE
Redskins 30-Oct-07 Carlos Rogers CB KNEE
Redskins 19-Dec-07 Rocky McIntosh LB KNEE
Saints 26-Jul-07 Steve Gleason S KNEE
Saints 1-Aug-07 Lance Legree DT KNEE
Saints 26-Sep-07 Deuce McAllister RB KNEE
Saints 13-Dec-07 McKinley Boykin DT KNEE
Saints 24-Dec-07 Mike McKenzie CB KNEE
Saints 26-Dec-07 Dante Ridgeway WR KNEE
Seahawks 2-Jan-07 Jimmy Williams CB KNEE
Seahawks 1-Sep-07 Marcus Tubbs DT KNEE
Seahawks 3-Oct-07 Alvin Pearman RB KNEE
Seahawks 17-Oct-07 Chuck Darby DT PATELLAR TENDON
Seahawks 4-Dec-07 C.J. Wallace S KNEE
Steelers 29-Nov-07 Dante Kreider RB KNEE
Texans 2-Aug-07 Chris Taylor RB KNEE
Texans 2-Aug-07 Roc Alexander CB KNEE
Texans 11-Sep-07 Jason Simmons S KNEE
Texans 25-Sep-07 Steve McKinney C KNEE
Texans 8-Nov-07 Dunta Robinson CB KNEE
Texans 4-Dec-07 Chris White C KNEE
Texans 9-Dec-07 Ahman Green RB KNEE
Titans 6-Aug-07 Antonio Johnson DT KNEE
Titans 1-Sep-07 Rien Long DT KNEE
Titans 30-Oct-07 Ken Amato LB KNEE
Vikings 12-Aug-07 Rufus Alexander LB KNEE
Vikings 9-Dec-07 Erasmus James DE KNEE
49ers 18-Dec-06 Jay Foreman LB MCL
49ers 12-Dec-06 Donald Strickland CB KNEE
49ers 23-Aug-06 Jeremy Newberry C KNEE
Bengals 29-Dec-06 Rich Braham C KNEE
Bengals 7-Nov-06 Adam Keift TE KNEE
Bengals 7-Nov-06 Breg Brooks CB KNEE
Bengals 2-Sep-06 Bennie Brazell WR KNEE
Bengals 21-Aug-06 Rashad Bauman CB PATELLAR TENDON
Bills 16-Oct-06 Josh Stamer LB KNEE
Broncos 21-Nov-06 Nick Ferguson S KNEE
Broncos 7-Nov-06 Sam Brandon S KNEE
Broncos 23-Oct-06 Matt Lepsis TE ACL
Broncos 12-Oct-06 Courtney Brown DE KNEE
Broncos 6-Jun-06 Landon Trusty TE ACL
Browns 19-Dec-06 Jason Wright RB KNEE
Browns 11-Dec-06 Orpheus Roye DT KNEE
Browns 29-Nov-06 Ethan Kelley DT KNEE
Browns 24-Oct-06 Gary Baxter CB KNEE
Browns 18-Oct-06 William Green RB KNEE
Browns 19-Sep-06 Daylon McCutcheon CB KNEE
Browns 30-Sep-06 William Green RB KNEE
Browns 30-Aug-06 DeMario Minter CB KNEE
Browns 31-Jul-06 LeCharles Bentley C KNEE
Buccaneers 5-Dec-06 Michael Clayton WR KNEE
Buccaneers 27-Nov-06 Dan Buenning G KNEE
Buccaneers 12-Oct-06 Andrew Economos C KNEE
Buccaneers 5-Oct-06 Kenyatta Walker T KNEE
Buccaneers 2-Sep-06 Torrin Tucker T KNEE
Cardinals 19-Dec-06 Adam Bergen TE KNEE
Chargers 29-Aug-06 Phil Archer LB KNEE
Chiefs 29-Oct-06 Will Svitek TE KNEE
Chiefs 18-Oct-06 Ronnie Cruz RB KNEE
Chiefs 2-Sep-06 Alphonso Hodge CB ?
Colts 24-Oct-06 Mike Doss S KNEE
Cowboys 12-Oct-06 Ryan Hannam TE KNEE
Dolphins 30-Dec-06 Keith Traylor DT KNEE
Dolphins 27-Dec-06 Eddie Jackson CB KNEE
Dolphins 19-Dec-06 Jeno James G KNEE
Dolphins 12-Dec-06 Daunte Culpepper QB KNEE
Dolphins 3-Sep-06 Joe Toledo T MCL
Eagles 21-Nov-06 Donovan McNabb QB ACL
Eagles 19-Sep-06 Jevon Kearse DE KNEE
Eagles 2-Sep-06 Stefan Rodgers T KNEE
Falcons 31-Jul-06 Brian Finneran WR KNEE
Giants 26-Dec-06 Chad Morton RB ACL
Giants 11-Nov-06 Amani Toomer WR KNEE
Jaguars 29-Aug-06 Greg Jones RB ACL
Jaguars 29-Aug-06 Brian Jones TE KNEE
Jets 12-Aug-06 Sione Pouha DT KNEE
Lions 6-Dec-06 Shaun Rogers DT KNEE
Lions 30-Nov-06 Rex Tucker G KNEE
Lions 9-Nov-06 Brian Calhoun RB KNEE
Lions 17-Oct-06 Shawn Bryson RB KNEE
Lions 4-Sep-06 Tyrone Hopson G KNEE
Lions 29-Aug-06 Bill Swancutt III DE MCL
Packers 16-Dec-08 Mike Montgomery DE KNEE
Packers 3-Sep-06 Mike Hawkins CB KNEE
Panthers 20-Dec-06 Mike Rucker DE KNEE
Panthers 5-Oct-06 Mike Seidman TE KNEE
Panthers 12-Sep-06 Travelle Wharton T KNEE
Patriots 19-Dec-06 Ken Walter P KNEE
Patriots 9-Dec-06 Donald Davis LB KNEE
Raiders 29-Dec-06 LaMont Jordan RB KNEE
Raiders 14-Dec-06 Lance Johnstone DE KNEE
Raiders 29-Nov-06 Adam Treu C KNEE
Raiders 29-Aug-06 DeJuan Green RB KNEE
Rams 7-Nov-06 Tony Fisher RB KNEE
Rams 16-Sep-06 Andy McCollum C ACL
Ravens 20-Dec-06 Dan Cody LB KNEE
Ravens 5-Dec-06 Justin Green RB KNEE
Redskins 23-Dec-06 Marcus Washington LB KNEE
Redskins 13-Sep-06 Pierson Prioleau S KNEE
Saints 29-Nov-06 Ernie Conwell TE KNEE
Saints 12-Oct-06 Roman Harper S KNEE
Saints 30-Sep-06 Rob Ninkovich DE ACL
Saints 13-Sep-06 Keith Joseph RB KNEE
Saints 3-Sep-06 Jermane Mayberry G KNEE
Seahawks 12-Dec-06 Craig Terrill DT KNEE
Seahawks 11-Nov-06 Marcus Tubbs DT KNEE
Seahawks 2-Sep-06 Kemp Rasmussen DE KNEE
Steelers 20-Dec-06 Chad Brown LB KNEE
Steelers 1-Nov-06 Verron Haynes RB KNEE
Steelers 1-Nov-06 Arnold Harrison LB KNEE
Steelers 28-Aug-06 Ulish Booker T KNEE
Texans 16-Dec-06 Jameel Cook RB KNEE
Texans 14-Nov-06 Zach Wiegert G KNEE
Texans 17-Oct-06 Seth Payne DT KNEE
Texans 12-Sep-06 Roc Alexander CB KNEE
Texans 2-Sep-06 Domanick Williams RB KNEE
Titans 13-Dec-06 Antwan Odom DE KNEE
Titans 15-Nov-06 David Givens WR KNEE
Titans 13-Oct-06 Erron Kinney TE KNEE
Vikings 19-Dec-06 Spencer Johnson DT KNEE
Vikings 14-Nov-06 Jason Glenn LB KNEE
Vikings 19-Sep-06 Erasmus James DE ACL
Vikings 17-Aug-06 Chad Greenway LB KNEE
Vikings 7-Aug-06 Tank Williams S KNEE CAP
Vikings 3-Jun-06 Joey Goodspeed RB KNEE
Raw Num = Total Number of Season Ending Knee Injuries 2006-2008 per position
Avg # on Roster = Average Number of Players of that Position on a Team’s Roster
Norm Num = Raw Num/Avg # on Roster to normalize the data
References
AOL Sports. Retrieved 24 November 2008 from http://sports.aol.com/search/.
Bradley, James P; et al (2002). Anterior Cruciate Ligament Injuries in the National Football League: Epidemiology and Current Treatment Trends Among Team Physicians. In Arthroscopy. Vol. 18. No. 5. Pp. 502-509.
Lawrence, Mark. Football 101: Knees and Cartilage. Retrieved 20 November 2008 from http://football.calsci.com/Knees.html.
NFL Transactions List. Retrieved 23 November 2008 from http://www.nfl.com/transactions
Richard Stockton College Athletic Training. Retrieved 22 November 2008 from http://www.stockton.edu/ospreys/ACL/NflAcl.htm.
Bradley, Sekiya, Kaplan (2001). A Summary of ACL Injuries in the NFL. In Pro Football Athletic Trainer; 19(2): 2001, 4-5.