BIO-MECHANICS OF KNEE JOINT

Lecture-1

At the end of this lecture the student should be able to:

Describe basic characteristics of the knee joint

Identify structural adaptation of the knee joint

Enumerate basic anatomy of the proximal articular surface of the knee joint

OBJECTIVES

Introduction

The knee complex is one of the most often injured joints in the human body.

This anatomic complexity is necessary to allow for the elaborate interplay between the joint’s mobility and stability roles.

The knee joint works in conjunction with the hip joint and ankle to support the body’s weight during static erect posture.

Dynamically, the knee complex is responsible for moving and supporting the body during a variety of both routine and difficult activities.

The fact that the knee must fulfill major stability as well as major mobility roles is reflected in its structure and function.

The knee complex is composed of two distinct articulations located within a single joint capsule: the tibiofemoral joint and the patellofemoral joint.

The tibiofemoral joint is the articulation between the distal femur and the proximal tibia.

The patellofemoral joint is the articulation between the posterior patella and the femur.

Although the patella enhances the tibiofemoral mechanism, the characteristics, responses, and problems of the patellofemoral joint are distinct enough from the tibiofemoral joint to warrant separate attention.

The superior tibiofibular joint is not considered to be a part of the knee complex because it is not contained within the knee joint capsule and is functionally related to the ankle joint.

The double condyloid knee joint is defined by its medial and lateral articular surfaces, also referred to as the medial and lateral compartments of the knee.

Structure of the Tibiofemoral JointThe tibiofemoral, or knee, joint is a double

condyloid joint with three degrees of freedom of angular (rotatory) motion.

Flexion and extension occur in the sagittal plane around a coronal axis through the epicondyles of the distal femur,

medial/lateral (internal/external) rotation occur in the transverse plane about a longitudinal axis through the lateral side of the medial tibial condyle, and

abduction and adduction can occur in the frontal plane around an anteroposterior axis.

FemurThe proximal articular surface of the knee joint is

composed of the large medial and lateral condyles of the distal femur.

Because of the obliquity of the shaft of the femur, the femoral condyles do not lie immediately below the femoral head but are slightly medial to it

As a result, the lateral condyle lies more directly in line with the shaft than does the medial condyle.

The medial condyle therefore must extend further distally, so that, despite the angulation of the femur’s shaft, the distal end of the femur remains essentially horizontal.

The lateral femoral condyle is shifted anteriorly in relation to the medial femoral condyle.

In addition, the articular surface of the lateral condyle is shorter than the articular surface of the medial condyle.

When the femur is examined through an inferior view the lateral condyle appears at first glance to be longer.

However, when the patellofemoral surface is excluded, it can be seen that the lateral tibial surface ends before the medial condyle.

FEMUR:The two condyles are separated inferiorly by

the intercondylar notch through most of their length but are joined anteriorly by an asymmetrical, shallow groove called the patellar groove or surface that engages the patella during early flexion.

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