The Knee Joint
The knee joint is a modified hinge joint in that, as well as flexion and extension, a small amount of internal and external rotation can occur. There also exists the gliding joint at the patella-femoral joint anteriorly.
The two condyles of the femur articulate with the corresponding condyles of the tibia. The underside of the patella glides in the femoral groove on the anterior aspect of the lower part of the femur.
A tough strong tissue surrounds the joint, but is absent at the front. It is lined by synovial membrane which produce synovial fluid.
Ligaments (Fig 1)
The knee is strengthened by a number of ligaments.
- Medial Collateral Ligament – this is wide and strap like and extends from the medial condyle of the femur about four fingers breadths below the joint line to the medial surface of the tibia.Its deeper fibres attach to the medial meniscus.
- Lateral Collateral Ligament – this is short and cord like. Can be felt on the lateral side of the knee. Extends from the lateral condyle of the femur to the head of the fibula.
- Cruciate Ligaments – the two cruciate ligaments lie inside the capsule and are named according to their attachment to the tibial plateau. The Anterior Cruciate Ligament (ACL) attaches to the anterior part of the superior surface of the tibia, fromhere it runs upwards, backwards and laterally to the lateral condyle of the femur. The Posterior Cruciate Ligament (PCL) attaches to the most posterior part of the superior surface on the tibial plateau and runs upward, forward,s and medially to attach to the medial condyle of the femur. These ligaments are very strong. They help prevent forward and backward displacement of the tibia on the femur respectively.
- Patellar Ligaments – Lies on the anterior aspect of the knee attaching the apex of the patella to the tibial tuberosity. It acts as a tendon for the quadriceps muscle group.
- Coronary Ligament – This attaches to the outer part of the cartilage (meniscus) to tibial plateaus.
Menisci (Cartilages) (Fig 3)
These are ‘C’ shaped pieces of fibro cartilage which sit on top of their corresponding condyles of the tibia. The upper surface of the meniscus is smooth and concave and in contact with the condyles of the femur. They are wedged shaped being thicker on the outer part than the inner part.
The medial meniscus is attached to the medial collateral ligament. The functions of the menisci are:
a) Shock absorption and weight bearing
b) Aids in rotation of the joint
The largest sesamoid bone in the body, it’s underside articulates with the patella groove of the femur to form the Patella Femoral Joint.
The patella has two functions:
a) Improve the mechanical efficiency of the quadriceps muscle in the final degrees of extention.
b) Offers some protection to the anterior aspect of the knee joint.
Added by :Eddie Jackman
Acupuncturist,Physical Therapist and Sports Therapist based in Waterford
For treatments or appointments please call 087 6701166