A schematic of the new view of bone. University of Cambridge

There is “goo” in our bones.

According to new findings made by scientists at Cambridge University in the UK, the minerals that make bones contain a “goo” that is trapped between tiny crystals. The substance lubricates, allows for movement and allows for for flexibility to prevent them bones from breaking.

The latest study published March 24 in the journal Proceedings of the National Academy of Sciences describes how the “goo” which is a mixture of the chemical citrate and water. The two substances combined create a viscous fluid that is trapped between nano-sized crystals in bones. The fluid gives the crystals some wiggle room, acting as a shock absorber so the bones are flexible under pressure.

"This nano-scopic layering of citrate fluid and mineral crystals in bone means that the crystals stay in flat, plate-like shapes that have the facility to slide with respect to each other,” Dr. Melinda Duer, who led the study said in a statement. “Without citrate, all crystals in bone mineral would collapse together, become one big crystal and shatter.”

Duer and her colleagues came to their conclusion after using a combination of NMR spectroscopy, X-ray diffraction, imaging and high-level molecular modelling to reveal the citrate layers in bone.

The same way two panes of glass with water in the middle would be able to stick together and slide, Duer says the same goes for bones.

“You've got to have something that keeps the water there, stops it from drying out and stops the plates from either flying apart or sticking fast together. We now know that thing is citrate," Duer said.

Citrate is able to bond easily to calcium. Not only does this allow for the mineral crystals to be held together, but it also prevents them from fusing and gives them the ability to trap water. "Without citrate, water would just flow straight through these gaps," Duer said.

While citrate may have already been pinpointed as a key component in bone’s nanostructure, the latest study is one of the first to propose a new structure for bone mineral where citrate in hydrated layers creates a bridge for mineral platelets.

“It's this layered structure that's been missing from our knowledge, and we can now see that without it you're stuffed,” Duer said.