3D Scanning and 3D Printing Reveal the Evolutionary Roots of Joint Pain

Evolution is a jerk sometimes. Sure, humans have come a long way and done amazing things, and it’s incredible to think that we are the descendants of four-footed creatures. However, the millennia-long process of transforming into the species we are today hasn’t been perfect, and some University of Oxford researchers are studying how evolution may be responsible for some painful and aggravating conditions many of us currently face, especially as we get older.

The Oxford Orthopaedic Evolutionary Group was formed by Clinical Lecturer Dr. Paul Monk, Zoology Professor Fritz Vollrath, and Professor of Orthopaedic Surgery and Musculoskeletal Science Dr. Jonathan Rees. The group’s research studies the evolutionary origins of human bones, how they turned into the skeletal structure we have now, and the ways in which they may be responsible for orthopaedic problems today.

I know very few adults who don’t experience some sort of recurring or chronic joint pain that seems to come from nowhere. Back problems and knee issues are everywhere, afflicting people seemingly without regard to size, diet or level of physical activity. The reason for this, according to the Oxford researchers, may go all the way back to when humans began walking on two legs – apparently our bodies didn’t adapt to it as well as they should have.

Dr. Paul Monk

“We see certain things very commonly in hospital clinics – pain in the shoulder with reaching overhead, pain in the front of the knee, arthritis of the hip, and in younger people we see some joints that have a tendency to pop out,” said Dr. Monk. “We wondered how on earth we have ended up with this bizarre arrangement of bones and joints that allows people to have these problems. And it struck us that the way to answer that is to look backwards through evolution.”

Looking backwards involved taking CT scans of 224 ancient bone specimens located at the University of Oxford, London’s Natural History Museum, and the Smithsonian Institution in Washington, D.C. Those scans, which were taken not only from humans and hominids but primates, dinosaurs and other animals, were used to create a library of 3D models, which the researchers studied and compared to track the changes in the shapes and structures of single bones over the course of millions of years.

One thing that they discovered was that the “neck” of the human thigh bone appears to have started growing thicker around the time humans started standing on two legs, which makes sense as the thigh bones would need to adapt to support the extra weight. Unfortunately, the thicker the femoral neck bone, the likelier it is that arthritis will develop – a good explanation for why so many adults suffer from hip pain.

Femoral neck bone of homo erectus (L) and homo sapiens

Even more unfortunately, if the human body continues to evolve in the same trajectory as it has for millions of years, the femoral neck bone will continue to get thicker, leading to more cases of arthritis. The researchers used the 3D models to 3D print the “skeleton of the future,” using a mathematical algorithm to predict how human bones will continue to change shape, and if their predictions are correct, it’s not just the hips that will develop worsening problems. The study also found that a gap in the shoulder, which allows tendons and blood vessels to pass through, has been growing narrower over time, which would account for the pain that some people have when they lift their arms over their heads.

“These models will enable us to identify the root causes of many modern joint conditions, as well as enabling us to anticipate future problems that are likely to begin to appear based on lifestyle and genetic changes,” said Dr. Monk. “Current trends reveal that the modern shapes of joint replacements won’t work in the future, meaning that we will need to re-think our approach for many common surgeries. We also wanted to see what we’re all going to look like in the future, and to answer questions such as ‘are we evolving to be taller and faster or weaker’, and ‘might we be evolving to need hip replacements earlier in the future?'”

Unlike the fossilized specimens of the past, future changes aren’t set in stone – there are a lot of unknown factors that could influence the way humans change and adapt in the future. The Oxford study, however, can give us an idea of what our descendants may look like, and the problems that they may face. You can see the interactive 3D models here. Discuss in the Evolution forum at 3DPB.com.