Interstitial fluid flow
Also called: fluid shear flow, lacunar-canalicular fluid flow
What it means
Interstitial fluid flow is the movement of fluid through tiny channels in bone that happens when bone bends, creating a signal that bone cells use to sense loading.
This fluid flow is thought to be the key way your bone cells detect loading, which is part of how your bones respond to the forces placed on them.
Interstitial fluid flow is the movement of fluid through the tiny channels in bone called canaliculi, which are only 0.1 to 0.5 micrometers wide. When bone bends under load, this fluid gets pushed through those channels, creating a shear force that brushes against the osteocytes living inside them.
This fluid movement is considered the main way osteocytes actually sense that bone is being loaded. The osteocytes have tiny arm-like dendrites floating in this fluid, and the shear stress from the flow is what triggers them to respond. Generally speaking, the faster and harder bone is loaded, the stronger the fluid flow and the stronger the signal sent to the osteocytes.
In simple terms, this is part of how your bones 'feel' the forces you put on them during movement, and how that physical signal gets translated into a biological one inside the bone.
How sure is this?
Graded Established Science: Supported by broad scientific consensus and decades of research. Read each study with its grade in mind. One study is a piece of the picture, not the whole of it.
Where the Academy teaches it
This page is the short version. The lessons teach it in full, with the context around it and a quiz to lock it in.
Questions people ask about this
When you push on bone, it actually bends very slightly — far too little to see, but enough at the microscopic level to squeeze fluid through tiny channels inside the bone. That fluid movement is what your bone cells sense, and it's the very first step in a chain of signals that tells your bone "you're using me."
Read the full answer →Related words
Osteocytes are the most common bone cells. They used to be bone-builders but got trapped inside bone tissue, where…
The lacunar-canalicular system is a network of tiny spaces and channels in bone where fluid moves when bone is…
Canaliculi are microscopic channels in bone that connect bone cells together and let fluid flow past them, helping…
Mechanotransduction is how bone cells sense physical force and turn it into chemical signals that tell bone to adapt.
Strain rate is how quickly a force is applied to bone, not just how much force there is — and faster loading tends…
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