Tendons and ligaments

Question 1

Describe, compare and contrast the structure of tendons and ligaments

Answer 1

Both tendons and ligaments are made up of fibrils. In tendons the fibrils are arranged longitudinally in parallel to maximize resistance to tensile forces. In ligaments the fibrils are aligned in parallel with some oblique or spiral arrangements to accommodate for forces in multiple directions.

Question 2

Describe, compare and contrast the stress-strain relationships observed in tendons and ligaments

Answer 2

The stress-strain relationship of tendons and ligaments is split into 3 parts. They are the toe region, linear region, and failure region. The toe region is when the fibers are straightened and stretched from their resting zig zag position. This is only up until 3% strain, at which point the linear region begins. This region is representative of the elastic capability of the tissue. In this region any strain that happens will not permanently deform the tissue. This goes up to 6%-10% of strain after which is the failure region, or the region where the strain is so high that the tissue will not be able to return to its initial form, undergoing plastic changes and an increased resting length.

Question 3

Describe the creep response in cartilage

Answer 3

Creep happens after a certain amount of deformation occurs causing a lasting change in length due to damage in the structure. For cartilage it is compressed and some of the fluid is excavated. After the load is removed the cartilage cannot return to its original shape as the fluid has decreased so when it is distributed it take up less volume.

Question 4

Describe “stress relaxation” response that can occur collectively in cartilage, tendons and ligaments due to their viscoelasticity.

Answer 4

When the structure is put under a load the deformation that occurs causes fluid to leave the structure. The remaining fluid is not evenly distributed at this point but will begin to evenly distribute throughout the structure until it is even. This is shown in the stress relaxation curve where the force gradually decreases until evening out. It comes to a new equilibrium due to the even distribution of fluid providing better support for the structure and decreasing the force on it.