Comments: The title of this study indicates that it sets out to examine the "effects of protective knee bracing on speed and agility", and it does indeed provide a lot of very useful insight. However, the major concern is that this study blurs the distinction between off-the-shelf functional (DonJoy Legend, Breg Tradition) knee braces and low-end protective-only devices (e.g. McDavid Knee Guard). This is not an apples-to-apples comparison. This same blurring of distinction extends to the authors' review of previous studies.

While an off-the-shelf or custom-made functional brace can of course be used to prevent injury (and in fact, such braces are far superior to low-end protective-only devices), keep in mind that a good-quality functional brace also requires the additional step of being properly fitted to the person's leg. Even off-the-shelf functional braces often require some fitting. (In this study, no customization of any brace to any person's leg was done. Granted, the braces were applied and adjusted by a certified orthotist/prosthetist, in accordance with manufacturer's directions, but this alone is not enough to ensure proper fit. In many cases, modifications to off-the-shelf braces, for example careful bending of frames, are appropriate; obviously, once such changes have been made to a certain brace, the entire brace would not be usable by anyone else after that. The braces provided for this study were provided free of charge, and thus it follows that no changes were made in order to preserve resale value of these products. Note that some people's leg shapes are such that no off-the-shelf device would fit properly. Such people should be provided with custom-made bracing...but no provision was made for that in this study.) Note that low-end protective-only device can cost as little as $50, whereas off-the-shelf functional braces can cost about $500. Custom-made functional braces can cost about $1000.

It should be kept in mind that because none of the braces in this study were custom-made, the general conclusions of this study should not be applied blindly towards custom-made bracing. However, the findings do apply to off-the-shelf braces (at least, the off-the-shelf braces tested). The finding that the Breg Tradition (now X2K) seriously impinged on agility (as measured by the four-cone drill) is not surprising, given that this off-the-shelf stamped-aluminum brace stands out as being heavy and rather cumbersome (especially when compared to carbon-fibre-composite off-the-shelf functional braces that are price-wise very similar). The only other functional-type brace in this study, the DonJoy Legend, is also made of aluminum, but it tends to be lighter than the Breg Tradition/X2K.

The authors point out that low-end soft neoprene-sleeve-with-struts prophylatic braces provide no more than 20% to 30% greater resistance to a lateral blow than in the non-braced condition. In contrast, a dual-hinged (i.e. one hinged strut, also known as an upright, on each side of the knee) hardshell functional brace (which can be off-the-shelf or custom-made) provides far better protection against such forcing, and ensures that the only way to force the knee sideways is to destroy the brace itself. The strength advantages of having a rigid frame with dual-upright design are clear from the viewpoint of structural engineering. It is physically impossible for a single-upright brace to be as strong as a dual-upright brace of the same mass. The dual-upright design will always be much stronger. (Please note: Even if an economy prophylactic brace consists of a neoprene sleeve with one hinged sheet-metal strut on each side of the knee, this is still nowhere near as good as a proper functional brace that incorporates a rigid frame that surrounds the knee and that has dual uprights.)

Functional bracing also provides reliable protection against injurious hyperextension (and, if so equipped, against hyperflexion as well). Here, again, a dual-upright construction is key to providing reliable protection against such forcing. Clearly, in cases where dependable protection against sideways forcing and injurious hyperextension is required, functional bracing should be specified. (Because the leg bones are surrounded by easily sheared soft tissues, it is inappropriate to expect a used-in-isolation functional brace to protect against twisting-type injuries. Athletes should understand this fundamental physical limitation of bracing, and should recognize that no brace is a license to be reckless.)

Note that the realm of off-the-shelf bracing includes all versions of the Breg Tradition (now sold as the X2K), given that any of Breg's models sold as custom-made are in fact bent-to-shape off-the-shelf units. The Omni AKS 101W and McDavid Knee Guard, both low-end prophylactic-only braces, are basically upper and lower cuffs made of neoprene, with a single lateral hinged metal strut. Because they use a single-upright design, they are clearly are structurally very different from the aforementioned functional knee braces.

The second paragraph under the Introduction section of this article gives background information on how knee bracing can affect joint functioning. However, it is important to note that the influence of a brace on knee function depends not only on brace design and fit, but also on how it is worn. It is safest to anchor the lower shell of the brace firmly to the leg (with the strap just below the knee being tightest), and then have the upper-shell straps only moderately tight (albeit for functional braces the strap immediately above the knee can be tightened if anterior-drawer-counteraction forcing [described elsewhere] in desired, for an ACL-compromised knee). Having all straps gorilla-tight is counterproductive, given that it is physically impossible for the brace hinge to exactly match the complex multiplanar roll-and-glide motion of the knee (and also, each person's knee motion is slightly different anyway). If the topmost strap of the brace is left only moderately tight, then the thigh has a bit of room to move normally, and the brace's injury-protective capabilities (which depend on overall brace design, as noted earlier) are unaffected. Furthermore, avoiding overtightening the topmost strap ensures that the brace is not forced down the leg due to the cone-shaped thigh.