From Can knee braces cause breaks of the femur in the upper leg, the biggest bone in the body? We know knee braces more than halve the risk of common knee injuries. But some riders claim a knee brace will protect the knee but transfers the force to the femur in major accidents. While the femur is a very strong bone, these riders believe that a knee injury is preferable to a fractured femur in these major impacts. Unfortunately, there is almost no research and just anecdotal evidence that suggests braces could be involved in femur fractures for motocross riders.

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Do knee braces make a difference? Yes. The same study found that knee braces at least halved knee injuries for dirt riders, and suggested they have an even greater effect on the MCL which is injured by twisting motions. But what about femur fractures? There is good news from the biggest knee brace study to date. With over three thousand riders clocking up 40000 hours of riding. The incidence of motocross injuries: a 12-year investigation says all injuries most common from cornering when knee used as a pivot, at least in mx. next is from jumps. ACL from hyperextending landing from a jump, or losing balance on jump and putting leg out when landing, or foot slipping off the peg onto the ground. The same study of more than 2000 dirt riders found that 43% knee injuries were the ACL, the ligament that joins your upper and lower leg bones. 20% involved the meniscus, the cartilage that absorbs impacts to the joint, and 15% to the MCL, a ligament that prevents sideways movement of the knee joint. It would be good to see more studies done in this area, but to me, this strongly suggests there is very little risk of a femure fracture from knee braces for the average dirt rider. The anecdotal evidence suggests femur fractures for riders with knee braces appear to be more likely for the fast riders and those getting a lot of air on the big jumps. Fractures occur at the expected spot, where the top of the brace would push against the upper leg. So if riders aren’t racing or doing masive jumps then knee braces would seem to be a very sensible choice for all those minor to moderate impacts. What about motocross riders? A quarter of the riders in this study were in motocross, so this study does suggest the risk of a femur fracture would appear to be low, but ideally we need more research on this so riders can make informed decisions. There is a small but potentially deadly chance a broken femur can cut the femoral artery. If it’s a compound fracture, there is a risk of infection that can be life-threatening.
While a lot of fractures just mean six weeks in plaster, a femur fracture can take a long time to knit and involve surgery that has a small but significant chance of dangeous post-operative infections.

Any long bone fracture in the lower extremity is worse than a knee ligament injury. I think that having a knee joint, which is a naturally occurring break in the lower extemity, is a natural defense against long bone fractures which would be fatal in a caveman. Most of the MXers I have treated and/or advised on these websites were wearing knee braces when the fractured their femurs… While a knee injury is painful and takes a lot of rehabilitation, specialists believe in most cases theycan achieve a full, or nearly full recovery of knee function… Most of the femur fractures I have personally cared for and most of those that I have encountered while advising on this and other websites have curiously occurred at the upper junction of the brace and femur… My experience as a rider and as an orthopedic surgeon has led me to conclude that the best protection for the knee, and other parts too, is a high level of cardiovascular fitness, and riding skills. Over 30% of my practice comes from off-road motorcycle injuries. The typical mid-shaft femur fracture looks awful at the track but I’d rather treat it than a blown out knee. I can put a rod in the femur,
have the rider walking in two weeks, riding in six weeks and racing in twelve weeks! While I’ve heard people say that knee braces can cause femur fractures I know of no data that supports the claim. We have not found any statistically significant link between knee braces and fractures. I have certainly seen fractures in both cases.