Why do you get water on the knee after a replacement?

Fluid accumulation around the knee, also known as knee effusion or water on the knee, is a common occurrence following total knee arthroplasty (TKA), or knee replacement surgery. It is a normal part of the body's healing process and usually resolves over time. Here are a few reasons why water may accumulate on the knee after a knee replacement:

1. Post-Surgical Swelling: During and after surgery, the knee joint experiences trauma, and the surrounding tissues undergo inflammation. This inflammation causes increased fluid production and swelling, leading to the accumulation of fluid around the knee.

2. Lymphatic Drainage Impairment: The lymphatic system is responsible for draining excess fluid from tissues. After knee replacement surgery, the surgical intervention can disrupt the lymphatic vessels and impair lymphatic drainage, leading to fluid retention.

3. Blood Vessel Leakage: Small blood vessels in the knee joint can become damaged during surgery, causing leakage of blood and plasma into the joint space. This extra fluid can contribute to knee effusion.

4. Implant Reaction: Some patients may experience a reaction to the implant materials used in knee replacement surgery. This reaction can cause inflammation and fluid buildup around the joint.

5. Underlying Medical Conditions: Certain medical conditions, such as heart failure, kidney problems, or liver disorders, can also contribute to fluid retention and swelling in the body, including the knee.

6. Infection: In rare cases, infection after knee replacement surgery can cause inflammation and fluid accumulation in the knee joint.

In most cases, water on the knee after a knee replacement is a temporary condition that resolves as the healing process progresses. Physical therapy, elevation of the leg, and ice therapy can help reduce swelling and promote lymphatic drainage. If the fluid buildup is excessive or persistent, the healthcare provider may need to drain the excess fluid or investigate further to rule out any underlying issues.