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Knee anatomy

The knee joint is surrounded by a thick bag (capsule) and filled with synovial fluid, which keeps it lubricated. It lies between the thigh bone (femur) and the shin bone (tibia).

 

X-ray of Normal Lateral Knee

Normal Lateral Knee X-Ray

The knee is often discussed as a single joint, but it is actually comprised of two joints. The part of the knee formed between the end of the femur and the top of the tibia is called the tibio-femoral joint. The patello-femoral joint lies between the end of the femur and the kneecap (patella).

 

The bones of the knee joint are covered by a layer of smooth joint surface cartilage. This white, shiny lining of the knee allows smooth gliding of the joint surfaces. This lining is so smooth that the surfaces move without friction, like two ice cubes gliding on one another. This joint surface cartilage is also referred to as articular cartilage. If the joint surface cartilage is damaged either through injury or repeated wear and tear, arthritis develops. This form of arthritis is called osteoarthritis.

 

The other type of cartilage that we find in the knee is the meniscal or shock-absorbing cartilage ( "footballers cartilage" ). There are two meniscal cartilages in the knee, one on the inner (medial) side of the knee and the other on the inner (lateral) side. They sit between the curved lower part of the femur (femoral condyle) and the flat upper part of the tibia (tibial plateau). Their function is to share the load from the thigh bone to the shin bone (when walking) and to provide stability to the knee. Whenever the shock absorbers are damaged, their shock absorbing function is compromised. This in turn exposes the underlying articular cartilage to wear and tear and damage.

Important knee structures - view from the front
Knee Anatomy - view from the front



Important knee structures - view from the back
Knee Anatomy - view from the back

 

The knee is stabilised by 4 key ligaments. Sitting in the centre of the knee are the 2 cruciate or crossing ligaments. The front ( anterior ) cruciate ligament is called the Anterior Cruciate Ligament or ACL. This stops excessive forward movement of the shin on the thigh and more importantly controls rotation. The back or posterior cruciate ligament ( PCL ) prevents excessive backward movement of the shin on the thigh. Sitting either side of the knee are the collateral ligaments. On the inner or medial side is the Medial Collateral Ligament or MCL. On the outer or lateral side of the knee is the Lateral Collateral ligament. Further stability to the knee is provided by the back 'corners' of the knee, namely the postero-lateral and postero-medial corners of the knee, which may also be damaged at the time of injury.

 

The key muscles for knee flexion (bending) are the hamstrings, which are found at the back of the thigh. Conversely the muscles that straighten or extend the knee are the quadriceps, which sit at the front of the thigh. The quadriceps attach to the upper part of the kneecap (patella) via the quadriceps tendon. The lower part of the patella attaches to the tibia via the patellar tendon. An injury to any part of the “extensor mechanism” will prevent a patient from being able to straighten their leg and make walking very difficult.

 

Mr Wilson during a knee consultation

Mr Wilson during a knee consultation

Mr Wilson examining a patient's knee

Key-hole  knee surgery

Key-hole knee surgery

Surgical team during knee arthroscopy

Anaesthetist - Dr Nick J looking over the drapes

Anaesthetist - Dr Nick J looking over the drapes

Orthopaedic consultation

Orthopaedic consultation

Anterior cruciate ligament reconstruction

Anterior cruciate ligament reconstruction

Anterior cruciate ligament reconstruction

Anterior cruciate ligament reconstruction

Knee injection with PRP

Knee injection with PRP

Mr Wilson in surgery

Mr Wilson in surgery

Arthroscopic knee surgery

Arthroscopic knee surgery

Mr Wilson examining a patient's knee

Mr Wilson examining a patient's knee