Modeling and analysis of knee and hip joints

Biomechanics as an independent branch of science has gained considerable

importance over the last seven decades especially owing to its valuable medical

applications. Replacement of hip joint and knee components due to wear, injury or

even breakage caused by accidents or due to senility. Consequently, considerable

research has been intensively choosing suitable synthetic materials, conducting

experiments on musculoskeletal models and carrying out an appropriate finite

element analysis. However researchers have not concentrated on the detailed

analysis of various forces in the bones and muscles connected to the knee and hip

joints. Attention of researchers in recent past has been leaning more towards the

biological and medical fields than on the mechanical computations. The present

work aims at developing a representation of all the forces by the free body diagrams

of the hip and knee joints. To know the force or stress distribution in the hip and

knee joints of human being, one has to understand hip and knee anatomy.

Knee joint is a complicated assembly; force analysis of knee is carried out by

using principles of classical mechanics. Axial compressive and Muscle forces are the

two forces which acts on the knee joint, is determined for three different postures of

human being (standing, staircase accent and staircase decent). Hip joint is also

another intricate assembly; here force analysis of hip is also carried out by using

principles of classical mechanics. Axial compressive and ligament forces are the two

forces which acts on the hip joint, is determined for standing and bending postures

for various body weights of human being.

The two major bones involved in both knee and hip joints are Tibia and Femur.

In order to create 3D geometric models of these bones, image processing software is

used. The input source for image processing software is CT Scan slices (DICOM

images). The sequence of the slices is selected, by using scan image processing tools

like segmentation, volume rendering and various filters, three dimensional models

are created. Finally, fine mesh is generated to these bone models, these files are

saved as .stl format and imported to ANSYS 15.0. By providing the boundary

conditions to the 3D models of bones in ANSYS software, the Von-Mises stresses,

normal stresses and total deformations are evaluated for both the bones, Tibia and

Femur.