Knee Effusion

Knee effusion, also known as water on the knee, is a condition characterized by an abnormal accumulation of fluid within the knee joint.

Causes

• Trauma or injury to the knee, such as a blow to the knee or a sudden twisting motion
• Arthritis, including osteoarthritis, rheumatoid arthritis, and gout
• Infection, such as septic arthritis
• Bleeding disorders, such as hemophilia
• Tumors or cysts within the knee joint
• Overuse or repetitive strain on the knee joint

Symptoms

• Swelling of the knee, which may be accompanied by redness and warmth
• Pain or stiffness in the knee, especially with movement or weight-bearing activities
• Limited range of motion or difficulty bending or straightening the knee
• A feeling of tightness or fullness within the knee joint
• Difficulty walking or bearing weight on the affected leg

Diagnosis

Diagnosis of knee effusion typically involves a combination of physical examination, medical history, and imaging studies. The following tests may be used to diagnose knee effusion:

• Physical examination: A healthcare provider will examine the knee for signs of swelling, redness, and warmth, and assess range of motion and joint stability.
• X-rays: To rule out fractures or other bone-related problems.
• Magnetic resonance imaging (MRI): To evaluate soft tissue structures, such as ligaments, tendons, and cartilage.
• Ultrasound: To confirm the presence of fluid within the knee joint.
• Arthrocentesis: A procedure in which a needle is inserted into the knee joint to withdraw fluid for analysis.

Treatment

Treatment for knee effusion depends on the underlying cause and may involve a combination of the following:

• Rest, ice, compression, and elevation (RICE) to reduce pain and swelling
• Pain management with medications such as acetaminophen or ibuprofen
• Physical therapy to improve range of motion and strengthen surrounding muscles
• Arthrocentesis to drain excess fluid from the knee joint
• Surgery, in some cases, to address underlying conditions such as torn ligaments or cartilage damage

Complications

If left untreated, knee effusion can lead to complications such as:

• Persistent pain and stiffness
• Limited mobility and decreased function
• Infection or sepsis if the underlying cause is a bacterial infection
• Chronic joint damage or degeneration