Page 53 - ASOP ROT Study Guide

4 . 3 Types of movement
Under the action of the muscles the knee joint is able to carry out the following movements:
♦ Flexion - the tibia moves posteriorly in the sagittal plane
♦ Extension - the tibia moves to a straight line (or slightly more) relative to the femur in the
sagittal plane
As we have seen, rotation is possible but the ligaments are more important than muscles in
producing it. There is very little adduction/abduction (motion about our axis two above) unless
injury has occurred.

4 . 4 Muscles
When we were studying the hip we saw that it was surrounded by the bodies of the muscles that
cross it. The knee is different, having mainly the tendons of its muscles around it. This means that
the joint edges are easy to feel but it also means the joint is quite exposed to injury. Most of the
important muscles of the knee are found around the thigh.

4 . 4 . 1 Extensors
The quadriceps muscle has been described in the previous section (the hip). Its insertion into the
tibia is via the patella. The patella is joined to the quadriceps by a very short tendon called the
quadriceps tendon. From the inferior border of the patella the very strong patellar tendon passes
to the front of the tibia and is attached at a "bump" on the bone known as the tibial tubercle.
The patella is a sesamoid bone. Sesamoid bones are bones set in tendons and they occur
elsewhere such as in the hand and foot. Their function is not always obvious and the numbers
present vary between individuals, suggesting that they are not always essential.
In the case of the knee the patella is important and always present. Its function is to increase the
efficiency of the quadriceps muscle in extending the knee.

4 . 4 . 2 Flexors
The hamstrings were described in section on the hip. As well as being extensors of the hip they
are also flexors of the knee. The gastrocnemius muscles (Figure 16) which act across the knee
joint, are secondary flexors. At the knee they are primarily muscles of posture and balance.

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