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About KNEE SURGERY

Over 200,000 patients in the USA undergo knee replacement surgery each year, and the prime reason is painful arthritis. The three main forms of arthritis causing knee pain are osteoarthritis, traumatic and rheumatoid arthritis. When severe pain, stiffness and swelling is no longer treatable with medication, the sufferer may need replacement of the knee with a metal prosthesis.

Anatomy and Physiology

• The knee is a complex mechanism formed by the joining of bones, ligaments, muscles and protective cartilage (Figure 1)
• Bones

Femur. The femur or thighbone extends from the hip to the knee and forms the upper aspect of the knee

Tibia. The tibia is the major bone in the lower leg, sometimes called the shinbone. The tibial plateau is the portion of the tibia that forms the lower aspect of the knee

Fibula. The fibula is a slightly shorter bone that runs parallel and along the outside of the tibia Patella. The small bone in front of the knee: the kneecap

Major ligaments

Medial collateral ligament---limits inward bending of the knee. This ligament extends from the lower end of the femur on the medial side (inside) of the knee to the tibia

Lateral collateral ligament---limits outward bending of the knee. This ligament extends from the lower end of the femur on the lateral side (outside) of the knee to the fibula

Anterior cruciate ligament--- This is a rope like ligament that runs from the center of the femur to the anterior aspect (front) of the tibia. It is a major stabilizer of the knee that prevents the femur from rotating and sliding back on the tibia (Figure 2)

Posterior cruciate ligament--- This is a rope like ligament that runs from the center of the femur to the to the posterior aspect (back ) of the tibia. It works to stabilize the knee by preventing the femur from rotating and sliding forward on the tibia

Muscles

The quadriceps muscle ends in the patellar tendon that covers the patella

The hamstring muscles strengthen the back of the knee

Cartilage

Smooth white cartilages cushion the knee, line the surface of the femur, tibia and patella within the joint

Menisci are C-shaped cartilages sandwiched between the femur and tibia, one on the inside (medial meniscus) and one on the outside side of the knee (lateral meniscus)

Synovium is a special tissue that lines all motion joints and produces a lubricating fluid

Knee function

The knee is not just a simple hinged joint that bends backward (flexion) It also has a rotary motion that locks the femoral condyles into the tibial plateau on straightening (extension) the leg

On extension of the knee, the ligaments become tight and convert the knee into a rigid locked structure The knee unlocks on flexion allowing the increased range of motion seen as the lower leg swings backward