Infection of the knee joint

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It is a known fact that the knee is a complex structure comprised of cartilage, ligaments and other components that facilitate movement of two adjacent bones. The joint is lubricated by the synovial fluid which allows it to move. The fluid in the knee joint can become severely infected which is known as septic arthritis. Always remember that the knee is one of the common sites where joint infections occur.

What are the symptoms of infection of the knee joint?

The symptoms of septic arthritis include severe joint pain, high fever, warmth and redness of the skin covering the joint and diminished range of movement. In some cases, individuals can initially notice joint effusion which is commonly called as water on the knee. Children who have infection of the knee joint can appear irritable, sick and have poor appetite. If you suspect that an individual has any of the symptoms of septic arthritis, it is best to seek emergency care.

Knee joint infection
The symptoms of septic arthritis include severe joint pain, high fever, warmth and redness of the skin covering the joint and diminished range of movement.


There are various ways in which bacteria can spread into the joint space and cause an infection. The following are common causes of infection of the knee joint:

  • Direct piercing trauma to the knee
  • Spread of infection close to the knee
  • Bacterial infection via the bloodstream

Other risk factors for infection of the knee joint include diabetes, conditions that affect the joints such as rheumatoid arthritis and conditions that weaken the immune system.

Diagnosing infection of the knee joint

Assessment of the fluid in the knee is vital in order to determine a diagnosis of septic arthritis and to identify the causative bacteria. A needle is administered beneath the kneecap and the fluid is aspirated. The fluid aspirated is taken to the laboratory for analysis. Other tests that can be performed include MRI to detect if there is an accompanying bone infection. Blood culture can also be requested to determine the presence of bacteria in the bloodstream.

Treatment for infection of the knee joint

The treatment for septic arthritis typically involves draining the fluid in the joint space and administration of antibiotics. Once drainage is performed, it will help reduce the pressure in the joint and allows identification of the causative microorganism. Primarily, medical treatment is done with the help of broad-spectrum intravenous antibiotics that can get rid of a wide range of bacteria. Once the bacteria are identified, the treatment can be modified to oral antibiotics. In case there is no microbe recognized, an extended course of intravenous antibiotics might be required to completely eliminate the infection.

Important considerations to bear in mind

The early identification and timely treatment of knee infections is vital in order to prevent long-term complications. If an infection of the knee joint is not treated right away, septic arthritis can lead to chronic inflammation of the joint and deformity of the knee which can make walking a difficult task as well as limiting the normal movement of the leg.

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