University of Bath

Exploring the biomechanics of cartilage

Cartilage is a soft tissue that allows smooth articulation of bones. It has a complex internal structure that when damaged cannot be easily repaired.

Strain field on cartilage samples
Strain field in articular cartilage visualised with digital image correlation

Articular cartilage distributes the joint loads during daily activities. It provides smooth and almost frictionless motion of the bones with very low wear rates. These remarkable properties are a direct result of cartilage’s complex internal structure. When this structure is disrupted, for example by injury, the wear processes start leading to painful joints. More often, it leads to the development of osteoarthritis. The biggest problem with damaged cartilage is that there is no cure. There are some cases when the tissue auto repairs, but generally once the cartilage is damaged, the joint degenerates over time. This results in painful joint motion during daily activities.

To understand the mechanical behaviour of cartilage, Kinga Czerbak, PhD student and Mechanical Engineering graduate says: ‘My project aims to better understand the complex nature and structure of cartilage, how it can withstand large forces for such long periods of time, and how we can apply this knowledge to better understand how osteoarthritis develops and progresses.'

This involves designing a series of experiments that observe and measure the strain through the thickness of the cartilage as it swells. These experiments allow us to see in real time how the tissue stretches and shrinks when submerged in salty water. This shows us how it transports liquids in and out of its surface. This is interesting as cartilage doesn’t have any blood vessels within its structure. Cells are supplied with nutrients through the articular surface from the joint capsule.

The project also aims to create computational models of the tissue that will be validated through these experiments, to replicate cartilage natural behaviour. These models will allow for analysis of how changes in different material parameters of the tissue will affect its mechanical properties and response to load.