KNEE JOINT
1. This is the largest and most complex joint.
2. It is a hinge joint formed by the condyles
of the femur, the condyles of the tibia and the posterior surface of the
patella.
3. The anterior part of the capsule is formed
by the tendon of the quadriceps femoris muscle, which also supports the
patella.
4. Intracapsular structures include two
cruciate ligaments that cross each other, extending from the intercondylar
notch of the femur to the intercondylar eminence of the tibia.
5. They help to stabilize the joint.
6. Semilunar cartilages or menisci are
incomplete discs of white fibrocartilage lying on top of the articular condyles
of the tibia.
7. They are wedge shaped, being thicker at
their outer edges, and provide stability.
8. They prevent lateral displacement of the
bones, and cushion the moving joint by shifting within the joint space
according to the relative positions of the articulating bones.
9. Bursae and pads of fat are numerous.
10. They prevent friction between a bone and a
ligament or tendon and between the skin and the patella. Synovial membrane
covers the cruciate ligaments and the pads of fat.
11. The menisci are not convered with synovial
membrane because they are weight bearing.
12. External ligaments of the joint provide
further support, making it a hard joint to dislocate.
13. The main ligaments are the patellar
ligament, an extension of the quadriceps tendon, the popliteal ligaments at the
back of the knee and the collateral ligaments to each side.
Muscles and movements
v
Possible
movements at this joint are flexion, extension and a rotator movement that
‘locks’ the joint when it is fully extended.
v
When the
joint is locked, it is possible to stand upright for long periods of time
without tiring the knee extensors.
v
The main
muscles extending the knee are the quadriceps femoris, and the principal
flexors are the gastrocnemius and hamstrings.
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