How do doctors drain water on the knee?

Doctors drain water from the knee using a procedure known as knee arthrocentesis or needle aspiration. Here's a step-by-step explanation:

1. Preparation:

- The patient is comfortably positioned, usually lying down with the knee slightly bent.

- The knee area is cleaned and sterilized using antiseptic to minimize the risk of infection.

- A local anesthetic may be used around the puncture site to numb the area and minimize discomfort during the procedure.

2. Locating the Fluid Collection:

- The doctor uses ultrasound imaging to locate the area of fluid accumulation within the knee joint. This helps guide the needle placement and ensures accurate drainage.

3. Needle Insertion:

- A thin, hollow needle is inserted into the knee joint under ultrasound guidance. The needle is typically inserted through the side of the knee, just above or below the kneecap.

4. Fluid Drainage:

- A syringe is attached to the needle, and the doctor gently pulls the plunger to create suction. This allows the excess fluid to be drawn out of the knee joint. The synovial fluid, which is the fluid that lubricates the joint, is drained into the syringe.

5. Fluid Analysis:

- Some of the drained fluid may be sent to the laboratory for analysis. This can help identify any underlying conditions or infections that may be causing the knee effusion.

6. Completion and Bandaging:

- Once sufficient fluid has been drained, the needle is slowly removed, and the puncture site is covered with a bandage. The patient may be advised to keep the knee elevated for a period of time to minimize swelling.

Knee arthrocentesis is a simple and relatively quick procedure, usually taking less than 30 minutes. It provides relief from knee pain and swelling caused by fluid buildup and allows doctors to examine the joint fluid for further diagnosis.