The knee is a complex pivotal hinge joint that connects the bones in the upper and lower leg, comprised of muscle, ligaments, tendons, and the meeting of four bones: the femur, tibia, fibula, and patella. It is the largest joint in the body.  Read More
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In Depth: Knee

The knee is a complex joint that flexes, extends, and twists slightly from side to side. 

The knee is the meeting point of the femur (thigh bone) in the upper leg and the tibia (shinbone) in the lower leg. The fibula (calf bone), the other bone in the lower leg, is connected to the joint but is not directly affected by the hinge joint action. Another bone, the patella (kneecap), is at the center of the knee.

Two concave pads of cartilage (strong, flexible tissue) called menisci minimize the friction created at the meeting of the ends of the tibia and femur.

There are also several key ligaments, a type of fibrous connective tissue, that connect these bones. The four key ligaments of the knee are:

  • Anterior cruciate ligament (ACL)
  • Medial collateral ligament (MCL)
  • Lateral collateral ligament (LCL)
  • Posterior cruciate ligament (PCL)

Damage to the ACL, such as a tear, is a common knee injury among athletes. Severe injuries to this important ligament typically involve reconstructive surgery

Another common sporting injury is pulling or straining the hamstring tendons, two groups of string-like connective tissues at the back of the knee and thigh that connect some of the major muscles of the knee.

A dislocated kneecap is yet another common knee condition. The kneecap slides along a groove in the femur as the knee bends. It is held in place by a ligament at the bottom and a tendon on top. Those connect to the femur and tibia. Sometimes, due to numerous complications, the kneecap comes out of its groove and becomes dislocated. The proper term for this condition is patellar subluxation. It is most often treated with bracing and physical therapy.

Knee problems and knee pain are common as the knee is a frequent point of contact during traumatic accidents and is as prone to wear and tear due to its weight-bearing nature. It is also a common site for arthritis pain.

Other knee problems include:

  • Fractured kneecap
  • Torn meniscus
  • Torn ligament
  • Torn hamstring muscle
  • Gout (a form of arthritis)

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