Hyperextension is not how you would re-injure your ACL skiing - it would be twisting of the tibia in relation to the femur head. Braces theoretically could help stabilize this, but that effect is not seen in the real world (see discussion below).
To be fair, there is still some disagreement among PT/Orthopods. So here's the deal:
That review does include safety (=reinjury) as an endpoint. Here's another review that more explicitly states the point. (
http://sph.sagepub.com/content/7/3/239.long )
"Eleven studies in the initial review evaluated this question, and no study demonstrated a clinically significant or relevant improvement in safety, range of motion including extension, or other outcome measures [note: this includes re-injury]. Given these studies and the expense of postoperative bracing, we do not include bracing following ACL reconstruction as part of our protocol. This was reinforced by an additional 6 studies published since 2005. None of these demonstrated an advantage from bracing."
And a skier specific discussion can be found here -
http://www.jospt.org/doi/full/10.2519/jospt.2012.4024
"There appears to be overwhelming evidence in the current literature that does not support the use of functional knee braces when returning to sport.5,7,19,29,31,37 The current position of the US ski team is that the use of functional knee braces is physician dependent. We recommend using a brace for 1 year, after which the decision to continue bracing during skiing is left to the athlete. Although a systematic review of 12 randomized controlled trials performed in 2007 by Wright and Fetzer45 found no evidence that pain, range of motion, graft stability, and protection from subsequent injuries were affected by the use of braces, we refer to 2 specific ski studies for supporting evidence. Kocher et al24 found that nonbraced skiers were 6.4 times more likely to sustain a knee injury, such as a meniscal tear, chondral injury, or medial collateral ligament tear, than unbraced ACL-deficient knees. Sterett et al41 found that subsequent injuries on ACL-reconstructed knees in professional skiers were 2.74 times more likely to occur on unbraced knees."
Those last two studies are NOT randomized - meaning they just looked at who wears a brace vs who doesn't. Is someone who wears a brace more likely to ski more conservatively and/or rehab more cautiously than someone who doesn't? Definitely. So there is no way to isolate the effect of bracing from the effect of being the type of person that wears a brace. This is why non-randomized studies are not acceptable evidence for determining which treatment to use - they are only for generating hypotheses that should be later tested in an randomized trial. Trials have been run on braces and they indicated no benefit, but they have not specifically been done on skiers (primarily because randomized control trials are extremely expensive and nobody is going to make any money off of telling people to not brace their knees)
TLDR: you can either trust two inadequate studies specific to skiers supporting bracing, or a multitude of adequate studies across a variety of sports that do not support it.
Your doctor and physio recommend the brace because it is the "standard of care", meaning it is what other physicians commonly do and it is probably what they were taught when they went through school/residency - NOT because there is good evidence for it. This protects them from a lawsuit if you were to re-injure your knee and try to sue them for whatever reason. Not to shit on doctors - I'll be one in May (hence my interest in this type of thing)- but this is one example of where the data does not support common practice.
