Professional mixed martial arts competition is a full-contact sport that has risen rapidly in popularity in recent years, setting numerous attendance and viewing records.1 2 Combining various combat techniques, a fighter seeks to win by knockout, referee stoppage, submission, or outscoring an opponent based upon the judges’ decision. Permissible fighting techniques may be broadly categorised as striking (including blows delivered by hands, feet, elbows or knees) and grappling (involving throws, take-downs, choke holds or submissions). The term “mixed martial arts” (MMA), is derived from proficiency at a wide set of skills adapted from different martial arts disciplines achieved through cross-training.

The earliest tournament style events held in the USA, in 1993, featured combatants trained in diverse martial arts styles who fought with virtually no protective gear, weight classes, time limits, or other regulatory standards.3 4 Although no deaths or permanently disabling injuries associated with this type of competition have been reported or are known to have occurred in the USA during this era, significant criticism was voiced over the perceived lack of attention to fighter safety, leading to highly publicised calls to ban such events.2

However, under new leadership, a concerted effort to earn public acceptance was launched by establishing specific rules and regulations that promote combat fighter safety. Working with state athletic commissions, MMA events were first sanctioned in the state of New Jersey in 2000, followed by Nevada in 2001.1 5 Strict adherence to established rules and regulatory standards has enabled MMA to establish a strong foothold in mainstream sports culture. Since its inception, Nevada has hosted the greatest number and most visible professional MMA competitions in the USA. The Nevada State Athletic Commission upholds the health and safety of fighters as one of its highest priorities, and formal recommendations have been made by its advisory committee to further investigate medical issues that affect the safety of the sport.6

Although a handful of studies have sought to characterise injuries sustained in no-holds barred fighting from the past, only one previous study has explored the incidence of injuries in professional MMA competition after sanctioning by an athletic regulatory commission.7^–9 With the marked increase in number of professional events taking place, these issues have gained heightened attention.

This study examined MMA injury patterns during a 5 year period after sanctioning in Nevada from 2002 to 2007.

METHODS

Institutional review board exemption was granted. A retrospective cohort study was conducted to examine MMA injury patterns during a 5 year period after sanctioning. Data from all regulated MMA competitions in the state of Nevada during the study period, from March 2002 to September 2007 (n = 635 matches), was obtained. All data are in the public domain and accessible on the website of the Nevada State Athletic Commission.10 Data obtained included the date and location of the matches, rounds scheduled, rounds fought, time ended, name of referee, competitors’ date of birth, weight, match outcome (win, loss or draw), how the matches ended (submission/tapout, technical knockout (TKO), knockout (KO), unanimous or split decision, physician stoppage, no decision or disqualification), and all officially reported injuries occurring during the match as documented by ringside physicians. Injuries were classified by the study team as lacerations, ocular injuries, facial injuries (including probable or suspected fracture), upper limb injuries (including probable or suspected fracture), lower limb injuries (including probable or suspected fracture), severe concussion, spine injuries (including suspected fracture), and all other injuries (eg torso and rib injuries, or otherwise unclassified).

Injury and outcome data for all sanctioned MMA matches were analysed according to two separate methods. First, a pair-matched case–control design examined injury patterns using conditional logistic regression based on match outcome, age, weight and fight experience. Cases were defined as fighters who sustained an injury during the matches, and controls were defined as fighters who were not injured. Second, a multiple logistic regression analysis explored factors including match outcome, age, fight experience, weight, combat minutes, and scheduled rounds that were potentially associated with increased likelihood of injury.

Data was analysed using Stata software V. 9.0. All tests were two-tailed, with significance set at p<0.05 and 95% CI. The ORs of injury after controlling for other covariates were evaluated by conditional logistic regression and multiple logistic regression.

RESULTS

In total, 635 MMA matches or 1270 fight exposures involving 636 separate competitors took place between March 2002 and September 2007 in Nevada. There were 629 winners, 629 losers, and 12 competitors whose matches ended in a draw (table 1).

With each round scheduled to last 5 minutes, 34 matches were planned for two rounds, 533 matches for three rounds, and 68 championship matches for five rounds. In total, 474 of the 635 (74.7%) matches ended early, representing 1185 of 2007 scheduled rounds of competition fought, or 4623 of 10 035 scheduled minutes. In descending order of frequency, 225 (35.4%) matches ended with submission, 214 (33.7%) matches ended by TKO, 155 (24.4%) matches ended with decision, 21 (3.3%) matches ended with KO, 10 (1.6%) matches ended by physician stoppage, 5 (0.8%) by disqualification, and 6 (0.9%) with a draw or no decision.

During the matches, 300 (23.6%) of the 1270 fighters sustained documented injuries. The injury rate was thus 23.6 per 100 fight participations or 64.9 per 1000 combat minutes. Of the injured fighters, 252 (84.0%) had one injury, 40 (13.3%) fighters had two injuries and 8 (2.7%) fighters had three injuries, resulting in 356 recorded injuries (table 2).

In our conditional logistic regression using a pair-matched, case–control design (232 pair-matched), a losing fighter was 2.53 times more likely to be injured than a winning fighter (OR = 2.53, 95% CI 1.88 to 3.42, p<0.01) after controlling for age, weight, and fight experience (table 3). Age, weight and fight experience did not statistically increase the likelihood of injuries after controlling for other covariates.

In our multivariate logistic regression of the entire cohort (n = 1270), a loser was 2.40 times more likely than a winner to be injured after controlling for age, weight, fight experience, and time of match termination (OR = 2.40, 95% CI 1.84 to 3.13, p<0.01). After controlling for other covariates, each minute increased the likelihood of injury by 4.2% (OR = 1.04, 95% CI 1.01 to 1.07, p<0.01). A three-round regular match was 4.46 times more likely to result in an injury than a two-round reality showcase match. Notably, age, weight, fight experience (based on previous fight number), and 5-round championship matches did not significantly increase the likelihood of injury after controlling for other covariates (table 4).

DISCUSSION

Professional MMA competition has experienced a surge in popularity in recent years, with increasing numbers of events held both in the USA and worldwide. However, few studies have explored the injury risks associated with this sport. Excluding work previously published by our group, a literature search of the term, “mixed martial arts injuries” yielded only two other articles. One study included only publicly available video-broadcast matches, and incorporated aggregate data from both sanctioned and unsanctioned MMA competition.4 7 A separate biomechanical study modelled the calculated force of various manoeuvres by analysing two subjects in a controlled research environment.8 Thus, understanding of the nature of MMA injuries, related factors and potential implications for fighter safety remains rather limited. To our knowledge, this study is the most comprehensive analysis of sanctioned professional MMA competition to date.

As expected, the results from both conditional and multiple logistic regression showed that a losing fighter was at considerably greater risk for sustaining injury, whereas other factors like greater age, increased weight or lesser fight experience were not found to be associated with injury. Actual time fought in minutes was associated with a slightly increased injury rate. Although there was no statistical difference in odds of injury between a regular three-round and five-round championship bout, those who fought in two-round reality showcase matches were less prone to sustaining injury, presumably due to its less competitive exhibition-style format.

A recent commentary from the British Medical Association illustrated some controversies that exist around MMA as a professional sport. In an earnest attempt to link MMA with boxing, the update asserted that “because of its ‘no holds barred’ nature, the [MMA] fighters are open to a myriad of injuries, including subdural haematoma, thought to be one of the most common causes of injuries in boxing.”11 12 The report further commented on the isolated death of a fighter in 1998. Of note, this fatality occurred in Ukraine, where an American fighter competed against medical advice outside the bounds and before implementation of MMA regulations by any official sanctioning organisation.4 13 Indeed, the current format of sanctioned MMA competition has undergone major changes from the original unregulated competitions. State licensing commissions have developed numerous rules and clear regulations with respect to weight classes, rounds, time limits and equipment, all geared toward improving fighter safety. In reality, modern professional MMA competition is not a “no holds barred” sport, but rather has been subject to strict rules since 2000, after sanctioning in New Jersey and Nevada.14 15 With increased numbers of regulated matches, the overall injury rate of 23.6 injuries per 100 fight participations is lower than previously reported.9 MMA invites comparison with boxing, which has seen rates ranging from 17.1 to 25 injuries per 100 fight participations;16 17 however, MMA and boxing are distinct sports with different equipment, rules and standards. Given the absence of direct comparative evidence, any implied association between patterns of MMA and boxing injuries deserves further investigation.

Moreover, it is essential to consider the distribution and severity of injuries sustained in MMA. For the purposes of discussion, a critical sports-related injury may include any persistent acquired brain injury, paralysis, permanent functional loss of limb or permanent blindness. Although some critics contend that MMA carries a major risk of severe injury, no deaths or critical sports-related injuries resulted from any of the regulated matches during the study period to our knowledge. In MMA competition, matches may end in a variety of ways other than knockout, such as by submission, referee stoppage or judges’ decision, all of which lower the odds of serious injury to the fighter. Nearly 60% of all matches we analysed ended by decision or submission, and 93.5% of all matches ended by decision, technical knockout or submission. Although fighters certainly can be injured during a technical knockout or submission, it is unusual to observe serious injury in these cases, due to referee intercession or voluntary tapout.

The most common reported injuries were lacerations and upper limb injuries, which appear to result mainly from striking. Loss of consciousness, despite its recognised limitations, has traditionally been used to grade the severity of concussive injury in sports.18^–21 Although loss of consciousness does not necessarily correspond with severity, there is no universally endorsed concussion grading scale.18 19 In this study, loss of consciousness resulting from a knockout was classified as severe concussion because it could be clearly and readily recognised.20 21 This translated into a severe concussion rate in regulated professional MMA competition of approximately 16.5 per 1000 athlete exposures, or 3.3% of all matches. In relative terms, this is comparable with the risk of concussion in world class international men’s tae kwon do competition.22 While not minimising the importance of other categories of reported injuries, cases involving severe concussion, a single reported case requiring exclusion of cervical fracture and two cases requiring exclusion of lumbar fractures deserve attention, as these injuries carry the greatest potential for critical sports-related injury.

A limitation of this study relates to the current availability of data regarding MMA injuries. Officially recorded injuries are based on physician reports at ringside. Given that the accuracy and exact nature of any reported injury in this study could not be directly confirmed by follow-up examination, neuropsychological testing, radiographic studies or other diagnostic methods, future studies to address this gap are needed. Steps to facilitate national or international sharing of appropriate de-identified MMA medical data for safety research purposes should be considered. Although the overall risk of critical sports-related injury may be overstated, formal diagnosis of acute traumatic brain injury and concussion requires assessment parameters that were not documented or not available. This may contribute to an underestimate of such injuries. Furthermore, although the absolute risk for chronic traumatic brain injury in combat sports such as modern-day boxing has been deemed by well-respected experts to be low, it is too early to determine whether such findings can be extrapolated to MMA.23

Although injury rates in regulated professional MMA competition are similar to other combat sports, the overall risk of critical sports-related injury appears low. Most sanctioned bouts end via decision or submission. Measures such as physician teams at ringside, and the ability of referees to intercede or for fighters to voluntarily concede may be important in minimising risk of serious injury. Additional study is warranted to achieve a better understanding of injury trends and ways to further lower injury risk in MMA.