Fallon Fox, the 37 year old transgender female fighter, has been at the center of controversy for the last few days. The question of the safety of her opponents has been on everyone's mind, and many a debate has been sparked over whether she should be allowed to fight professionally.

Yesterday, I wrote a post that featured a Q&A portion and quotes from interviews I conducted with two of the world's leading gender reassignment surgeons. The overall tone from the physicians' comments was that there was a strong probability that Fox might not carry much of a physical advantage into her fights with biologically born women.

This post will feature quotes from an interview I did with Dr. Johnny Benjamin, a leading, board certified orthopedic surgeon. Since many of the questions revolved around skeletal structure and bone density, I felt Dr. Benjamin was very qualified to give expert opinion on the subject. Here's what he had to say:

The whole transgender issue in female sports, is that people can't look at it rationally. It always becomes a huge social issue. 'Oh, you don't like transgender people.' I don't even know if I actually know any transgender people, but I certainly don't have hangups with people. Who you love, who you date ... I couldn't care less. I don't pick who you love, you don't pick who I love. That's a rule I live my life by. What a grown person does is there own business.

The issue here is if it's safe or not. That's the only thing I care about. Do we know enough about it to say if it's safe or not? The problem with the transgender issue, specifically male to female, is that there is not enough scientific information out there to say if it's safe enough to allow this to go on. If you don't know if it's safe, we have to err on the side of safety, which says until we get more information, we cannot go forward with this.

One of the things that's very interesting, is everyone says, 'Well there's been a few studies that say after two years this, that and the other...' That's not true. There's no studies for this. I've done the literature search. Then they come back with, 'The IOC knows.' The IOC knows what? The IOC caved to political and social pressure. The IOC didn't say, 'Because of firm scientific and medical evidence, that if you've had this SRS and you've taken hormones for two years, that's the magic number that all this is going to become safe.' That's not true at all.

There is no firm scientific basis to support that conclusion. They made an arbitrary determination in the face of social pressure. OK, I understand that, too. Who wanted to fight the fight? The IOC didn't want to, so they said. 'If you get the surgery and take the hormones for two years, that's good enough for us.' That doesn't mean it was made on a sound medical basis, because the sound medical basis doesn't exist. Those studies have not been done.

The surgeons that spoke towards bone density decreasing and so on and so forth - that doesn't say the person doesn't still have superior physiological abilities. The real question is, what was the sex at time of puberty? As we all know, boys and girls aren't that much different until they go through puberty.

Gender reassignment happens after puberty. One of the things that happens during puberty, is that boys grow 15-20 cm taller than girls. The average height of men is greater than the average height of women. In addition to bone density, there is also the issue of longer bones in men. Longer bones lead to some mechanical advantages that shorter bones don't have.

The argument is that "They've become a woman because they've had the surgery and taken the hormones.' The hormones will certainly make your phenotype. The different hormone therapies are very good at changing that, but they don't change those things that happen to you during puberty. The length of your bones don't change. The mean muscle surface area doesn't change a great deal.

When people say, 'That person has turned into a woman', I'm fine with that, but where is the hard scientific data that says their athletic performance capacity has now changed to that of a woman? That scientific research has not been done.

People might think I'm against transgender people. I'm not against anybody. That's a social issue. What I'm saying is that we don't know enough, and if you don't have that knowledge, if you don't have that scientific information, you have to err on the side of safety. Until we know for sure, I can't support it. We simply don't know what the safety issues are.

The rest of this interview covered other safety issues, namely head trauma and TRT in combat sports, and will be published in two additional pieces over the next couple days, so keep a look out for those.

You can follow Dr. Benjamin via his Twitter, @DrJCBenjamin