Complications

Complications of a swollen knee can include:

• Muscle loss. Fluid in the knee can harm the working of your muscles and cause thigh muscles to weaken and atrophy.
• Fluid-filled sac (Baker's cyst). The buildup of fluid in your knee can lead to the formation of a Baker's cyst in the back of your knee. A swollen Baker's cyst can be painful, but usually improves with icing and compression. If the swelling is severe, you might need to have fluid removed (cyst aspiration).