Knee Osteoarthritis in the Fighting Arts and Combat Sports

Among athletes, knee injury is a predisposing factor towards the development of knee osteoarthritis (OA). (Molloy & Molloy, 2011). Other joints may be at risk for overuse injuries and OA, but it is the knees in particular that seem to occupy a special place in the realm of chronic injuries.  Recognizing the risks of an activity allows for the development of injury-prevention programs specific to it’s demands and conditions. Although many martial artists don’t identify themselves as athletes, the demands of training are inherently athletic and the effects of training on the body are no different from those of athletic training.

Fighting arts and sports pose inherent risks to joint health, particularly acute or chronic injuries associated with the knees. A case by case analysis of the training activities and priorities of the various combat sports and so-called martial arts  would be necessary to discuss the risk of a certain format or style, but several mechanisms of injury are common to many:

  • rapid and asymmetrical loading and unloading of joints during throws, tackles, sweeps, etc.
  • bounding, cutting and darting movements, often under external load or force
  • impact trauma from falls, kicks, sweeps
  • compressive, shearing, tension and torsional trauma from joint manipulations

As reported by Zetaruk & colleagues (Zetaruk, Violan, Zurakowski & Micheli, 2004) lower limb injuries make up a considerable percentage of self-reported injuries amongst surveyed regular (3 h/wk) practitioners of various martial arts. Lower limb injuries (unspecified) constituted 85 out of 263 injuries sustained by students of karate, Aikido, kung fu, tae kwon do & tai chi. Although the data is drawn from sample groups ranging in size from 14 to 114 respondents per style, lower limb injuries are consistent across all groups. Arts that place a higher priority on kicking techniques showed a higher incidence of knee injury (Zetaruk, et al., 2004), which indicates that the practice of those techniques in itself (open chain/in the air or on targets) may account for the injuries more than actually receiving a blow.

Repetitive, open-chain repetitions of kicks as “basics” is common in many so-called traditional martial arts, and in itself can contribute to chronic knee injury and performance deficits. The most obvous mechanism is of compression in the joint as the bony articular surfaces lock in extension, and the cruciate ligaments are alternately loaded. Less obvious is alterations in joint stability. As the prime movers around the joint (the muscles that perform the bulk of the actions in question) become fatigued, the nervous system responds by “turning down” the amount of force they produce. Other muscles take over and the joint begins to move in a different pattern, which places all structures at increased risk for acute or chronic injury. If an inflated priority is not placed on high reps of such techniques, this mechanism of injury can be mitigated. Consider for a moment practices such as “fatigue the muscles until the technique is pure” or “let’s do a few hundred of these as a warm up.” These may seem like good, tough training methods for improving a student’s performance, but in actuality they reduce the amount of control, precision, and power that he or she might be capable of developing.

Grappling sports and arts may not involve strikes to the lower extremity, but the nature of many throws can expose the receiver’s knees to significant rotational force. In a study of the relationship of Judo techniques to injury rates (Barsottini, Guimaraeas, Renato de Morais, 2006), knee injuries were specifically reported. Among 53 male and 25 female judoka surveyed, knee injuries comprised 23% of 78 injuries. A throw known as tai otoshi (“body drop,” in which the thrower pulls the receiver in close and rapidly turns 180 degrees while extending a leg in the path of the receiver’s legs and disrupting the COG by extending the hips into the receiver’s) had the highest incidence of knee injuries on the part of the receiver. One reason for this association is that the knee of the receiver proximal to the thrower’s tripping leg can remain planted and trapped as the combined weight of both individuals rotates around it. Given that this is a basic and frequently used throw in practice and competition, the average practitioner has a high chance of being on the receiving end of the technique.

Interestingly, professional mixed martial arts (MMA) competitors (Bledsoe, Hsu, Grabowski, Brill & Li, 2006) show a significantly lower rate of knee injury. Given that MMA competition typically permits a wider range of techniques and targets, that grappling and striking techniques are employed, and that Muay-Thai style low kicks to the thighs are common, one might expect a higher rate of knee injuries. Out of 100 injuries reported in 171 MMA matches in the state of Nevada during one year, only 3 were knee injuries. The limitations of this study are obvious however, and a wider sample size would provide more conclusive information. Bledsoe & colleagues’ (Bledsoe et al., 2006) findings might be an indication that the higher priority on conditioning for fight athletes pays off in terms of injury prevention, or it may be an artifact of the competitive format. Recreational martial artists generally do not place a priority on the same quality of conditioning and programming as fight athletes, but the evidence strongly suggests that well-programmed injury prevention programs may be more efficacious in preventing such injuries than simply participating in the fighting art alone.

With an awareness of the knee (and general joint) risks posed by specific techniques, training methods and competitive formats, injury prevention strategies such as conditioning programs and safety guidelines can be created. The second part of this discussion will explore options for some of the examples given above. Monitor yourself and your students for signs and symptoms of osteoarthritis and adjust programming and training accordingly- respect the need for recovery and the long term results will be far better than simply pushing through more of the same.  Injury is not a sign of weakness, and admitting the causes of an injury is the first step in improving it and getting back to the business of training.

If you have questions about including OA prevention in your training or adjusting training to reduce the stress on an affected joint, contact us for consultation.


Barosottini, D., Guimaraes, A.E., & Renato de Morais, P. (2006). Relationships between techniques and injuries among judo practitioners. Revista Brasileirade Medicinado Esporte, 12 (1), 48-51.

Bledsoe, G.H., Hsu, E.B., Grabowski, J.G., Brill, J.D. & Li. G. (2006). Incidence of injury in professional mixed martial arts competitions. Journal of Sports Science and Medicine, CSSI, 136-142.

Molloy, M.G. & Molloy, C.B. (2011). Contact sports and osteoarthritis. British Journal of Sports Medicine, 45, 275-277

Zetaruk, M.N., Violan, M.A., Zurakowski, D., &Micheli, L.J. (2004). Injuries in martial arts: A comparison of five styles. British Journal of Sports Medicine, 39, 29-33.


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