Comments: This study looks specifically at prophylactic knee braces, as widely used for college football and other collision-type team sports. These brace are typically primitive hinged-strut (either just one hinged-strip-of-sheet-metal strut, or perhaps one on each side of the knee, but typically no actual frame) off-the-shelf braces specifically intended to prevent injury via sideways forcing or hyperextension (which are generally referred to as contact-type injuries). However, keep in mind that functional knee braces also provide this same protection, and so functional braces are very often used prophylactically as well. But functional braces (which typically have shells which surround the leg as well as struts and hinges on both sides of the knee, and thus are structurally and mechanically far superior to both single-upright and two-hinged-strut-but-no-actual-frame prophylactic braces) are designed to fit the knee more closely than prophylactic ones, and even a base-model off-the-shelf functional brace can be expected to fit more comfortably than a prophylactic brace. (Granted, a custom-made functional brace, the most expensive option, can be expected to be the most comfortable, as well as the most lightweight and most protective of all.) The reader should keep in mind that designs of all types of knee braces vary greatly. The prophylatic category, in particular, has recently seen the arrival of a number of shell-type prophylactic braces which are structurally quite similar to full-fledged off-the-shelf functional knee braces (and which are being marketed for motocross use); however, such high-end prophylactic braces are not really covered by the studies Najibi and Albright looked at. (The study by Greene included two off-the-shelf functional braces that are often used prophylactically: the DonJoy Legend and the Breg Tradition. The inclusion of the Greene study in this review raises some confusion because Najibi and Albright are therefore using "prophylatic" to designate both low-end protective devices and used-prophylactically off-the-shelf functional braces. Overall, however, the studies reviewed by Najibi and Albright were focused almost entirely on low-end, economy-grade prophylactic braces such as the McDavid Knee Guard, the DonJoy Protective Knee Guard, and the Anderson Knee Stabilizer. It should be noted that one aspect which adds to the confusion of bracing is that of identification. In the reviews of a number of studies, very vague descriptors such as "DonJoy brace" are used. DonJoy, like many brace manufacturers, carries many products ranging from simple neoprene sleeves to high-end custom-fabricated braces. The obvious confusion caused by inadequate descriptions of the braces can seriously affect the meaning of such prophylactic-bracing studies as well as subsequent studies which make reference to them.) Readers of this study should also keep in mind that it is possible (and common) to use a custom-made functional brace in a prophylactic capacity. Using such high-end functional bracing in this context would address the problems Najibi et al. noted with designed-for-economy prophylactic bracing.

Najibi and Albright, in reviewing a number of studies done by others, found that even the most basic prophylactic braces provide some protection against inwards forcing; however, many of these tests did not adequately simulate the high kinetic energy (remember that kinetic energy increases not only with mass, but with the square of speed) of contact-sport collisions. They also note that because a tightly-strapped-on brace can decrease blood flow, earlier onset of fatigue and discomfort might occur; this is especially a concern with single-upright prophylactic braces, because such braces depend heavily on very tight strapping to protect against the aforementioned forcing. (In contrast, a shell-type functional brace uses rigidity of the frame to provide such protection, and so there is no need to overtighten the strapping.) The authors additionally note that slippage, hence migration, of prophylactic braces is a serious concern. (Functional braces, if well-designed, well-fitted, and especially if custom-made, tend not to have this problem. With a well-designed and correctly fitted functional brace, only the strap immediately below and behind the knee must be tight, in order to ensure reliable anchorage of the brace on the leg. With such a brace, it is feasible to have the upper-shell straps only moderately tight. In contrast, with a low-cost prophylactic brace, the need to have all the straps very tight results in the entire brace being forced down the leg, given the cone-like shape of the thigh.) Keep in mind that noncontact knee injuries (generally taken to denote plant-and-twist injuries) are something which no prophylactic nor functional brace can protect against (unless the brace is attached to some device which encases the ankle, a situation which is seems impractical for all sports except alpine skiing).

It seems safe to say that a non-knee-injured competitive athlete desiring protection against sideways forcing and injurious hyperextension might wish to eschew a cheap prophylactic brace and instead consider a good-quality, well-designed, dual-upright frame-type off-the-shelf functional brace (or even a custom-made functional brace) -- together with, of course, an exercise program (set up and supervised with input from a physiotherapist) which focuses on honing both leg-musculature strength and endurance, along with specific knee-injury-prevention training exercises (such as those from programs originally marketed as being for female-athlete knee-injury prevention; these exercise programs, for example Cincinnati Sportmetrics, are now recognized as being valuable for male athletes as well).

As a final note, players and coaches should understand that using a knee brace is not a license to be reckless. Nor is a brace a license to plant and twist with impunity. Nor is it a substitute for well-maintained leg musculature. The use of any type of knee bracing in a blanket-type (e.g. all or many of the players on a given football team) prophylactic capacity could conceivably engender the "revenge effect", whereby braced players take greater risks than they normally would. (This same phenomenon was observed some time ago, when the old-style thin leather football helmets were replaced by the modern thickly-padded hard-plastic ones. The players unwisely began using their heads as battering rams, thus engendering a number of horrific cases of instant quadriplegia. Numerous other examples of the revenge effect can be drawn from a wide variety of activities. As the helmet example shows, the revenge effect can easily result from equipment which does not directly enhance performance. All what is necessary for the revenge effect to occur is for the person to feel safer, and therefore become willing to take risks which he/she would have considered unsafe before. In other words, if giving someone any type of protection-conferring equipment results in a marked change in said person's behaviour and attitude towards risk, then this sets the stage for the revenge effect.) Given the large number of factors to take into account, and given the sizeable logistical problems inherent in designing a study to take into account these factors, it is to be expected that the outcomes of prophylactic-knee-bracing studies vary considerably: some find such bracing to be beneficial, while others find no reduction in injury rates.