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Magnetic Resonance Imaging–Documented Chondral Injuries About the Knee in College Football Players: 3-Year National Football League Combine Data
Magnetic Resonance Imaging–Documented Chondral Injuries About the Knee in College Football Players: 3-Year National Football League Combine Data Kurt C. Hirshorn, M.D., M.P.H., Taylor Cates, M.D., and Scott Gillogly, M.D.
Purpose: To evaluate the incidence and risk factors for knee cartilage injury in elite college football players invited to attend the US National Football League (NFL) Scouting Combine over a 3-year period. Methods: All players entering the NFL Scouting Combine (National Invitational Camp) from 2005 through 2007 were evaluated. “At-risk” knees underwent magnetic resonance imaging (MRI), and the results were evaluated for chondral injuries. Results: During the 3-year period reviewed, a total of 980 players were available for analysis, and a total of 516 players’ knee MRI scans were obtained (53% of all players at the Combine). The total number of full-thickness chondral injuries evident on MRI was 197 (20.1%) among all players, or 38.2% of the players who had an MRI scan. Of the players, 30 (3.06% of all players at the Combine, or 5.8% of the players who had an MRI scan) had isolated medial compartment full-thickness chondral injuries, 41 (4.2%, or 7.9%) had isolated lateral compartment full-thickness chondral injuries, 48 (4.9%, or 9.3%) had patellofemoral compartment full-thickness chondral damage, and 78 (7.96%, or 15.1%) had full-thickness chondral injuries in more than 1 compartment. Conclusions: The epidemiologic and risk assessment data presented in this study offer a cross-section of a young and elite athletic population who were “prescreened” at the NFL Combine over a 3-year period and judged to have at-risk knees. The total number of full-thickness chondral injuries evident on MRI was 197 (20.1%) among all players, or 38.2% of the players who had an MRI scan: 30 players (3.06%, or 5.8%) had an isolated medial compartment full-thickness chondral injury, 41 players (4.2%, or 7.9%) had an isolated lateral compartment full-thickness chondral injury, 48 players (4.9%, or 9.3%) had isolated patellofemoral compartment full-thickness chondral damage, and 78 players (7.96%, or 15.1%) had full-thickness chondral injuries in more than 1 compartment. Level of Evidence: Level IV, diagnostic study.
E
ach year at the National Football League (NFL) Scouting Combine (National Invitational Camp), approximately 330 of the nation’s best collegiate football players are invited to display their skills and abilities with the hope of being drafted by an NFL team. The Combine is a central tryout for all the NFL teams. In addition to speed, strength, and agility testing, an integral
From the Atlanta Medical Center (K.C.H., T.C., S.G.) and Atlanta Sports Medicine (S.G.), Atlanta, Georgia, U.S.A. The authors report no conflict of interest. Received June 5, 2009; accepted January 27, 2010. Address correspondence and reprint requests to Kurt C. Hirshorn, M.D., M.P.H., Atlanta Medical Center, 1810 Burlington Pl, Atlanta, GA 30307, U.S.A. E-mail: [email protected] © 2010 by the Arthroscopy Association of North America 0749-8063/9334/$36.00 doi:10.1016/j.arthro.2010.01.025
component of the process is the medical evaluation. Injuries are a key factor in the ranking and draft status and, ultimately, the perceived value of the player. In this environment, magnetic resonance imaging (MRI) is used liberally to evaluate any concerning history or physical finding. The low threshold for ordering MRI is this select group of athletes offers an outstanding opportunity to examine chondral injury patterns. NFL prospects were chosen as the sample population for a number of reasons. From the 180-lb safety to the 300-lb lineman, the variation in body size and habitus provides an inclusive and diverse study population. Most players entering the NFL draft are less than 22 years of age and at the pinnacle of physical condition. However, many of the knees of these athletes have deteriorated to conditions well beyond their chronologic age.1-6 Chondral injuries in a young, competitive athlete are an extremely difficult problem.7-12
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 26, No 9 (September), 2010: pp 1237-1240
1237
1238
K. C. HIRSHORN ET AL.
FIGURE 1. MRI example of a 21-year-old tight end at the NFL Scouting Combine. The left knee shows 2 cm of full-thickness cartilage loss on the posterolateral aspect of the medial femoral condyle (arrow).
Prior studies have reported on general injury prevalence among college football players, including a recent review of injury patterns in the elite college Big Ten football conference13 and a general review of NFL Combine rankings and injuries.14 This study specifically analyzes MRI-documented chondral injuries about the knee in this very active, young population. By presenting this report, our hope is to help characterize the important orthopaedic problem of cartilage injury in the young elite athlete. Our hypotheses were that there would be a high incidence of chondral injury and that injury prevalence would be directly related to body mass index (BMI) and position. METHODS Before we initiated our retrospective chart review, institutional review board approval was obtained. From 2005 through 2007, all players invited to the annual NFL Combine were screened for knee injuries (N ⫽ 980). Height, weight, and BMI measurements were taken at the start of the Combine. All players were given extensive physical examinations by board-certified orthopaedic surgeons who were unaware of the study. Any player with a history of injury/surgery or abnormal knee examTABLE 1.
ination findings was further evaluated by MRI and plain radiographs that day. Examinations were performed on a 1.5-T MRI scanner by use of coronal proton density, coronal inversion recovery, oblique sagittal proton density, oblique sagittal T2, axial gradient echo, and axial T2 fat saturation sequences. In addition, T2-weighted oblique coronal and oblique sagittal sequences along the length of the anterior cruciate ligament (ACL) were obtained. An additional set of fat-suppressed intermediate density–weighted images was also obtained. Studies were read by fellowship-trained musculoskeletal radiologists who were also unaware of the study. MRI and plain film findings were recorded in a database along with position, height, weight, BMI, and surgical history (Fig 1). Statistical analysis with odds ratios, logistic regression with interaction, and classification trees was performed. RESULTS During the 3-year period reviewed, a total of 980 players were available for analysis, and a total of 516 players’ knee MRI scans was obtained (53% of all players at the Combine). The mean age of the players attending the Combine in this study is 22 years (range, 20 to 23
Location and Frequency of Full-Thickness Cartilage Injury of All Players at NFL Screening Combine Compared With Players Who Had Knee MRI Scans Location Chondral Injury
All patients (N ⫽ 980) Patients who had MRI (n ⫽ 516)
Isolated Medial (MFC) Isolated Lateral (LFC) Isolated Patellofemoral Multiple Chondral Chondral Lesion Chondral Lesion Chondral Lesion Lesions
197/980 (20.1%)
30/980 (3.06%)
41/980 (4.2%)
48/980 (4.9%)
78/980 (7.96%)
197/516 (38.2%)
30/516 (5.8%)
41/516 (7.9%)
48/516 (9.3%)
78/516 (15.1%)
Abbreviations: MFC, medial femoral condyle; LFC, lateral femoral condyle.
CHONDRAL INJURIES AT NFL COMBINE TABLE 2.
Knee Chondral Injury and Weight
TABLE 3.
1239
Knee Chondral Injury and BMI
Weight
No. of Players
% With Chondral Injury
BMI
No. of Players
% With Chondral Injury
⬍222.5 lb ⬎222.5 lb
381 599
14 24
⬍30.5 ⬎30.5
462 518
15 25
years). The total number of full-thickness chondral injuries evident on MRI was 197 (20.1%) among all players, or 38.2% of the players who had an MRI scan. Of the players, 30 (3.06% of all players, or 5.8% of players with MRI scans) had an isolated medial compartment fullthickness chondral injury, 41 (4.2%, or 7.9%) had an isolated lateral compartment full-thickness chondral injury, 48 (4.9%, or 9.3%) had isolated patellofemoral compartment full-thickness chondral damage, and 78 (7.96%, or 15.1%) had full-thickness chondral injuries in more than 1 compartment (Table 1). We used a classification-tree model to look at what values of weight, BMI, and height gave players the highest risk of a chondral injury. An increased BMI was definitively shown to be associated with chondral injury in this population, specifically in quarterbacks, offensive tackles, and defensive backs. The cutoff value at which BMI increased the risk of chondral injury was 30.5. Increased weight above 222.5 lb was also shown to be significant for chondral injury. Only 14% of the 381 players who weighed less than 222.5 lb had a chondral injury, whereas 24% of the 599 players who weighed more than 222.5 lb had a chondral injury. Only 15% of the 462 players with a BMI less than 30.5 had a chondral injury, whereas 25% of the 518 players with a BMI greater than 30.5 had a chondral injury. Height was not shown to be a significant risk factor for chondral injury.
The results concerning weight and BMI of all players are summarized in Tables 2 and 3, respectively. In the evaluation of positional relation, we found that linebackers had the greatest prevalence of chondral injury (32.2%). Conversely, defensive backs were found to have the lowest prevalence of chondral injury (12.9%). These results were statistically significant when compared with various other positions (Fig 2). DISCUSSION This study highlights the high prevalence (20.1%) of chondral injuries in the NFL recruitment classes of the past 3 years. The purpose of the study was to evaluate epidemiologic characteristics to identify risk factors for chondral injury to the knee in this specialized population. By studying the injury patterns in young and elite athletes, our study offers a cross-section into the cartilage health of some of the highest-demand knees in the world. In the analysis of risk factors for chondral injury, BMI and weight were strongly associated with knee cartilage damage. Although it is known that obesity plays a role in the typical degeneration of elderly knees, this study showed that both BMI greater than 30.5 and weight greater than 222.5 are risk factors for cartilage damage in this young athletic population. A higher BMI had a statistically increased risk of chon-
FIGURE 2. Chondral injury breakdown by position. (DE, defensive end; NT, nose tackle; OC/ OG, offensive center/guard; WR, wide receiver; OT/WT, tackles; DB, defensive back; TB, tailback/running back; LB, linebacker; TE/FB, tight end/fullback; QB, quarterback; K, kicker.)
Proportion with Chondral injury
0.40
0.30
0.20
0.10
0.00 DE
NT
OC/OG
WR
OT/WT
DB
position
TB
LB
TE/FB
QB
K
1240
K. C. HIRSHORN ET AL.
dral injuries in quarterbacks, offensive tackles, and defensive ends. NFL physicians and trainers, as well as health personnel from other arenas, should be aware that optimizing weight offers a method by which cartilage injury can be minimized. Players can be informed that longevity may be enhanced by remaining as lean as possible. Alternatively, excessive weight risks damage to the knee joint and may place performance in jeopardy. These findings are likely explained by the dramatic amplification of force that is absorbed by the knee joint with even a moderate increase in body mass. In the analysis of position, linebackers were found to be at greatest risk for cartilage lesions. Our data suggest that the linebacker position is a stronger independent risk for knee cartilage damage than BMI. Under constant assault by offensive linemen and fullbacks and exposed to the rapid shear forces of a skill player, linebackers seem to be a “watershed” position. The mean BMI of the linebackers evaluated at the Combine over the 3-year period was 31.9. This combination of a high BMI and the position’s unique demands may explain the extremely high incidence of cartilage injury among players in the linebacker position. The weaknesses of this study include the very nature of the study—a retrospective review of preselected prospectively collected data. This study also has a selection bias: it included only the players being actively considered for drafting by the NFL and only those in whom knee injury was suspected based on history and examination findings. Moreover, we did not have MRI data on the asymptomatic players who may in fact have had subclinical cartilage damage. The data were preselected because only “suspect” players had MRI scans; this left an unaccounted 47% of the players without MRI data. MRI data, by nature, are limited in detecting all fullthickness chondral defects. The very nature of the Combine as a tryout would encourage the players to downplay positive history and examination findings. Regardless of these limitations, this study offers, at the very least, an underestimation of the true incidence of knee articular cartilage damage at the NFL Combine. The purpose of the NFL Combine, given the high stakes at risk, is to acquire as much information as possible and to give as accurate an estimate of a player’s risk as possible—with a bias, if anything, toward being more conservative. Weaknesses of this study also include failure to include information on chondral lesion size, acuity of the chondral injury, or mechanical alignment of the knee. These 3 variables are critical in terms of both management and prognosis.
CONCLUSIONS The epidemiologic and risk assessment data presented in this study offer a cross-section of a young and elite athletic population who were “prescreened” at the NFL Combine over a 3-year period and judged to have at-risk knees. The total number of full-thickness chondral injuries evident on MRI was 197 (20.1%) among all players, or 38.2% of the players who had an MRI scan: 30 players (3.06%, or 5.8%) had an isolated medial compartment full-thickness chondral injury, 41 players (4.2%, or 7.9%) had an isolated lateral compartment full-thickness chondral injury, 48 players (4.9%, or 9.3%) had isolated patellofemoral compartment fullthickness chondral damage, and 78 players (7.96%, or 15.1%) had full-thickness chondral injuries in more than 1 compartment. REFERENCES 1. Alford JW, Cole BJ. Cartilage restoration, part 1: Basic science, historical perspective, patient evaluation, and treatment options. Am J Sports Med 2005;33:295-306. 2. Blevins FT, Steadman JR, Rodrigo JJ, Silliman J. Treatment of articular cartilage defects in athletes: An analysis of functional outcome and lesion appearance. Orthopedics 1998;21:761-768. 3. Curl WW, Krome J, Gordon ES. Cartilage injuries: A review of 31,516 knee arthroscopies. Arthroscopy 1997;13:456-460. 4. Widuchowski W, Widuchowski J, Koczy B, Szyluk K. Untreated asymptomatic deep cartilage lesions associated with anterior cruciate ligament injury: Results at 10- and 15-year follow-up. Am J Sports Med 2009;37:688-692. 5. Widuchowski W, Lukasik P, Kwiatkowski G, et al. Isolated full thickness chondral injuries. Prevalance and outcome of treatment. A retrospective study of 5233 knee arthroscopies. Acta Chir Orthop Traumatol Cech 2008;75:382-386. 6. Sekiya JK, Ellingson CI. Meniscal allograft transplantation. J Am Acad Orthop Surg 2006;14:164-174. 7. Messner K, Maletius W. The long-term prognosis for severe damage to weight-bearing cartilage in the knee: A 14-year clinical and radiographic follow-up in 28 young athletes. Acta Orthop Scand 1996;67:165-168. 8. Shelbourne KD, Jari S, Gray T. Outcome of untreated traumatic articular cartilage defects of the knee: A natural history study. J Bone Joint Surg Am 2003;85:8-16. 9. Von Porat A, Roos EM, Roos H. High prevalence of osteoarthritis 14 years after an anterior cruciate ligament tear in male soccer players: A study of radiographic and patient relevant outcomes. Ann Rheum Dis 2004;63:269-273. 10. Zamber RW, Teitz CC, McGuire DA, Frost JD, Hermanson BK. Articular cartilage lesions of the knee. Arthroscopy 1989;5:258268. 11. Herbenick MA, King JS, Altobelli G, Nguyen B, Podesta L. Injury patterns in professional arena football. Am J Sports Med 2008;36:91-98. 12. Larsen E. Long-term outcome of knee and ankle injuries in elite football. Scand J Med Sci Sports 1999;9:285-289. 13. Albright JP, Powell J, Crowley E, et al. Injury patterns in big ten conference football. Am J Sports Med 2004;32:1394-1404. 14. Feeley BT, Kennelly S, Barnes RP, et al. Epidemiology of National Football League training camp injuries from 1998 to 2007. Am J Sports Med 2008;36:1597-1603.
Purpose: To evaluate the incidence and risk factors for knee cartilage injury in elite college football players invited to attend the US National Football League (NFL) Scouting Combine over a 3-year period. Methods: All players entering the NFL Scouting Combine (National Invitational Camp) from 2005 through 2007 were evaluated. “At-risk” knees underwent magnetic resonance imaging (MRI), and the results were evaluated for chondral injuries. Results: During the 3-year period reviewed, a total of 980 players were available for analysis, and a total of 516 players’ knee MRI scans were obtained (53% of all players at the Combine). The total number of full-thickness chondral injuries evident on MRI was 197 (20.1%) among all players, or 38.2% of the players who had an MRI scan. Of the players, 30 (3.06% of all players at the Combine, or 5.8% of the players who had an MRI scan) had isolated medial compartment full-thickness chondral injuries, 41 (4.2%, or 7.9%) had isolated lateral compartment full-thickness chondral injuries, 48 (4.9%, or 9.3%) had patellofemoral compartment full-thickness chondral damage, and 78 (7.96%, or 15.1%) had full-thickness chondral injuries in more than 1 compartment. Conclusions: The epidemiologic and risk assessment data presented in this study offer a cross-section of a young and elite athletic population who were “prescreened” at the NFL Combine over a 3-year period and judged to have at-risk knees. The total number of full-thickness chondral injuries evident on MRI was 197 (20.1%) among all players, or 38.2% of the players who had an MRI scan: 30 players (3.06%, or 5.8%) had an isolated medial compartment full-thickness chondral injury, 41 players (4.2%, or 7.9%) had an isolated lateral compartment full-thickness chondral injury, 48 players (4.9%, or 9.3%) had isolated patellofemoral compartment full-thickness chondral damage, and 78 players (7.96%, or 15.1%) had full-thickness chondral injuries in more than 1 compartment. Level of Evidence: Level IV, diagnostic study.
E
ach year at the National Football League (NFL) Scouting Combine (National Invitational Camp), approximately 330 of the nation’s best collegiate football players are invited to display their skills and abilities with the hope of being drafted by an NFL team. The Combine is a central tryout for all the NFL teams. In addition to speed, strength, and agility testing, an integral
From the Atlanta Medical Center (K.C.H., T.C., S.G.) and Atlanta Sports Medicine (S.G.), Atlanta, Georgia, U.S.A. The authors report no conflict of interest. Received June 5, 2009; accepted January 27, 2010. Address correspondence and reprint requests to Kurt C. Hirshorn, M.D., M.P.H., Atlanta Medical Center, 1810 Burlington Pl, Atlanta, GA 30307, U.S.A. E-mail: [email protected] © 2010 by the Arthroscopy Association of North America 0749-8063/9334/$36.00 doi:10.1016/j.arthro.2010.01.025
component of the process is the medical evaluation. Injuries are a key factor in the ranking and draft status and, ultimately, the perceived value of the player. In this environment, magnetic resonance imaging (MRI) is used liberally to evaluate any concerning history or physical finding. The low threshold for ordering MRI is this select group of athletes offers an outstanding opportunity to examine chondral injury patterns. NFL prospects were chosen as the sample population for a number of reasons. From the 180-lb safety to the 300-lb lineman, the variation in body size and habitus provides an inclusive and diverse study population. Most players entering the NFL draft are less than 22 years of age and at the pinnacle of physical condition. However, many of the knees of these athletes have deteriorated to conditions well beyond their chronologic age.1-6 Chondral injuries in a young, competitive athlete are an extremely difficult problem.7-12
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 26, No 9 (September), 2010: pp 1237-1240
1237
1238
K. C. HIRSHORN ET AL.
FIGURE 1. MRI example of a 21-year-old tight end at the NFL Scouting Combine. The left knee shows 2 cm of full-thickness cartilage loss on the posterolateral aspect of the medial femoral condyle (arrow).
Prior studies have reported on general injury prevalence among college football players, including a recent review of injury patterns in the elite college Big Ten football conference13 and a general review of NFL Combine rankings and injuries.14 This study specifically analyzes MRI-documented chondral injuries about the knee in this very active, young population. By presenting this report, our hope is to help characterize the important orthopaedic problem of cartilage injury in the young elite athlete. Our hypotheses were that there would be a high incidence of chondral injury and that injury prevalence would be directly related to body mass index (BMI) and position. METHODS Before we initiated our retrospective chart review, institutional review board approval was obtained. From 2005 through 2007, all players invited to the annual NFL Combine were screened for knee injuries (N ⫽ 980). Height, weight, and BMI measurements were taken at the start of the Combine. All players were given extensive physical examinations by board-certified orthopaedic surgeons who were unaware of the study. Any player with a history of injury/surgery or abnormal knee examTABLE 1.
ination findings was further evaluated by MRI and plain radiographs that day. Examinations were performed on a 1.5-T MRI scanner by use of coronal proton density, coronal inversion recovery, oblique sagittal proton density, oblique sagittal T2, axial gradient echo, and axial T2 fat saturation sequences. In addition, T2-weighted oblique coronal and oblique sagittal sequences along the length of the anterior cruciate ligament (ACL) were obtained. An additional set of fat-suppressed intermediate density–weighted images was also obtained. Studies were read by fellowship-trained musculoskeletal radiologists who were also unaware of the study. MRI and plain film findings were recorded in a database along with position, height, weight, BMI, and surgical history (Fig 1). Statistical analysis with odds ratios, logistic regression with interaction, and classification trees was performed. RESULTS During the 3-year period reviewed, a total of 980 players were available for analysis, and a total of 516 players’ knee MRI scans was obtained (53% of all players at the Combine). The mean age of the players attending the Combine in this study is 22 years (range, 20 to 23
Location and Frequency of Full-Thickness Cartilage Injury of All Players at NFL Screening Combine Compared With Players Who Had Knee MRI Scans Location Chondral Injury
All patients (N ⫽ 980) Patients who had MRI (n ⫽ 516)
Isolated Medial (MFC) Isolated Lateral (LFC) Isolated Patellofemoral Multiple Chondral Chondral Lesion Chondral Lesion Chondral Lesion Lesions
197/980 (20.1%)
30/980 (3.06%)
41/980 (4.2%)
48/980 (4.9%)
78/980 (7.96%)
197/516 (38.2%)
30/516 (5.8%)
41/516 (7.9%)
48/516 (9.3%)
78/516 (15.1%)
Abbreviations: MFC, medial femoral condyle; LFC, lateral femoral condyle.
CHONDRAL INJURIES AT NFL COMBINE TABLE 2.
Knee Chondral Injury and Weight
TABLE 3.
1239
Knee Chondral Injury and BMI
Weight
No. of Players
% With Chondral Injury
BMI
No. of Players
% With Chondral Injury
⬍222.5 lb ⬎222.5 lb
381 599
14 24
⬍30.5 ⬎30.5
462 518
15 25
years). The total number of full-thickness chondral injuries evident on MRI was 197 (20.1%) among all players, or 38.2% of the players who had an MRI scan. Of the players, 30 (3.06% of all players, or 5.8% of players with MRI scans) had an isolated medial compartment fullthickness chondral injury, 41 (4.2%, or 7.9%) had an isolated lateral compartment full-thickness chondral injury, 48 (4.9%, or 9.3%) had isolated patellofemoral compartment full-thickness chondral damage, and 78 (7.96%, or 15.1%) had full-thickness chondral injuries in more than 1 compartment (Table 1). We used a classification-tree model to look at what values of weight, BMI, and height gave players the highest risk of a chondral injury. An increased BMI was definitively shown to be associated with chondral injury in this population, specifically in quarterbacks, offensive tackles, and defensive backs. The cutoff value at which BMI increased the risk of chondral injury was 30.5. Increased weight above 222.5 lb was also shown to be significant for chondral injury. Only 14% of the 381 players who weighed less than 222.5 lb had a chondral injury, whereas 24% of the 599 players who weighed more than 222.5 lb had a chondral injury. Only 15% of the 462 players with a BMI less than 30.5 had a chondral injury, whereas 25% of the 518 players with a BMI greater than 30.5 had a chondral injury. Height was not shown to be a significant risk factor for chondral injury.
The results concerning weight and BMI of all players are summarized in Tables 2 and 3, respectively. In the evaluation of positional relation, we found that linebackers had the greatest prevalence of chondral injury (32.2%). Conversely, defensive backs were found to have the lowest prevalence of chondral injury (12.9%). These results were statistically significant when compared with various other positions (Fig 2). DISCUSSION This study highlights the high prevalence (20.1%) of chondral injuries in the NFL recruitment classes of the past 3 years. The purpose of the study was to evaluate epidemiologic characteristics to identify risk factors for chondral injury to the knee in this specialized population. By studying the injury patterns in young and elite athletes, our study offers a cross-section into the cartilage health of some of the highest-demand knees in the world. In the analysis of risk factors for chondral injury, BMI and weight were strongly associated with knee cartilage damage. Although it is known that obesity plays a role in the typical degeneration of elderly knees, this study showed that both BMI greater than 30.5 and weight greater than 222.5 are risk factors for cartilage damage in this young athletic population. A higher BMI had a statistically increased risk of chon-
FIGURE 2. Chondral injury breakdown by position. (DE, defensive end; NT, nose tackle; OC/ OG, offensive center/guard; WR, wide receiver; OT/WT, tackles; DB, defensive back; TB, tailback/running back; LB, linebacker; TE/FB, tight end/fullback; QB, quarterback; K, kicker.)
Proportion with Chondral injury
0.40
0.30
0.20
0.10
0.00 DE
NT
OC/OG
WR
OT/WT
DB
position
TB
LB
TE/FB
QB
K
1240
K. C. HIRSHORN ET AL.
dral injuries in quarterbacks, offensive tackles, and defensive ends. NFL physicians and trainers, as well as health personnel from other arenas, should be aware that optimizing weight offers a method by which cartilage injury can be minimized. Players can be informed that longevity may be enhanced by remaining as lean as possible. Alternatively, excessive weight risks damage to the knee joint and may place performance in jeopardy. These findings are likely explained by the dramatic amplification of force that is absorbed by the knee joint with even a moderate increase in body mass. In the analysis of position, linebackers were found to be at greatest risk for cartilage lesions. Our data suggest that the linebacker position is a stronger independent risk for knee cartilage damage than BMI. Under constant assault by offensive linemen and fullbacks and exposed to the rapid shear forces of a skill player, linebackers seem to be a “watershed” position. The mean BMI of the linebackers evaluated at the Combine over the 3-year period was 31.9. This combination of a high BMI and the position’s unique demands may explain the extremely high incidence of cartilage injury among players in the linebacker position. The weaknesses of this study include the very nature of the study—a retrospective review of preselected prospectively collected data. This study also has a selection bias: it included only the players being actively considered for drafting by the NFL and only those in whom knee injury was suspected based on history and examination findings. Moreover, we did not have MRI data on the asymptomatic players who may in fact have had subclinical cartilage damage. The data were preselected because only “suspect” players had MRI scans; this left an unaccounted 47% of the players without MRI data. MRI data, by nature, are limited in detecting all fullthickness chondral defects. The very nature of the Combine as a tryout would encourage the players to downplay positive history and examination findings. Regardless of these limitations, this study offers, at the very least, an underestimation of the true incidence of knee articular cartilage damage at the NFL Combine. The purpose of the NFL Combine, given the high stakes at risk, is to acquire as much information as possible and to give as accurate an estimate of a player’s risk as possible—with a bias, if anything, toward being more conservative. Weaknesses of this study also include failure to include information on chondral lesion size, acuity of the chondral injury, or mechanical alignment of the knee. These 3 variables are critical in terms of both management and prognosis.
CONCLUSIONS The epidemiologic and risk assessment data presented in this study offer a cross-section of a young and elite athletic population who were “prescreened” at the NFL Combine over a 3-year period and judged to have at-risk knees. The total number of full-thickness chondral injuries evident on MRI was 197 (20.1%) among all players, or 38.2% of the players who had an MRI scan: 30 players (3.06%, or 5.8%) had an isolated medial compartment full-thickness chondral injury, 41 players (4.2%, or 7.9%) had an isolated lateral compartment full-thickness chondral injury, 48 players (4.9%, or 9.3%) had isolated patellofemoral compartment fullthickness chondral damage, and 78 players (7.96%, or 15.1%) had full-thickness chondral injuries in more than 1 compartment. REFERENCES 1. Alford JW, Cole BJ. Cartilage restoration, part 1: Basic science, historical perspective, patient evaluation, and treatment options. Am J Sports Med 2005;33:295-306. 2. Blevins FT, Steadman JR, Rodrigo JJ, Silliman J. Treatment of articular cartilage defects in athletes: An analysis of functional outcome and lesion appearance. Orthopedics 1998;21:761-768. 3. Curl WW, Krome J, Gordon ES. Cartilage injuries: A review of 31,516 knee arthroscopies. Arthroscopy 1997;13:456-460. 4. Widuchowski W, Widuchowski J, Koczy B, Szyluk K. Untreated asymptomatic deep cartilage lesions associated with anterior cruciate ligament injury: Results at 10- and 15-year follow-up. Am J Sports Med 2009;37:688-692. 5. Widuchowski W, Lukasik P, Kwiatkowski G, et al. Isolated full thickness chondral injuries. Prevalance and outcome of treatment. A retrospective study of 5233 knee arthroscopies. Acta Chir Orthop Traumatol Cech 2008;75:382-386. 6. Sekiya JK, Ellingson CI. Meniscal allograft transplantation. J Am Acad Orthop Surg 2006;14:164-174. 7. Messner K, Maletius W. The long-term prognosis for severe damage to weight-bearing cartilage in the knee: A 14-year clinical and radiographic follow-up in 28 young athletes. Acta Orthop Scand 1996;67:165-168. 8. Shelbourne KD, Jari S, Gray T. Outcome of untreated traumatic articular cartilage defects of the knee: A natural history study. J Bone Joint Surg Am 2003;85:8-16. 9. Von Porat A, Roos EM, Roos H. High prevalence of osteoarthritis 14 years after an anterior cruciate ligament tear in male soccer players: A study of radiographic and patient relevant outcomes. Ann Rheum Dis 2004;63:269-273. 10. Zamber RW, Teitz CC, McGuire DA, Frost JD, Hermanson BK. Articular cartilage lesions of the knee. Arthroscopy 1989;5:258268. 11. Herbenick MA, King JS, Altobelli G, Nguyen B, Podesta L. Injury patterns in professional arena football. Am J Sports Med 2008;36:91-98. 12. Larsen E. Long-term outcome of knee and ankle injuries in elite football. Scand J Med Sci Sports 1999;9:285-289. 13. Albright JP, Powell J, Crowley E, et al. Injury patterns in big ten conference football. Am J Sports Med 2004;32:1394-1404. 14. Feeley BT, Kennelly S, Barnes RP, et al. Epidemiology of National Football League training camp injuries from 1998 to 2007. Am J Sports Med 2008;36:1597-1603.