The knee consists of a fluid called synovial fluid, which reduces friction between the bones of the knee joint while you move your leg. Sometimes this fluid is produced in excess, resulting in its accumulation in the back of your knee. A Baker's cyst or popliteal cyst is a fluid-filled swelling that develops into a lump behind the knee. This causes stiffness, tightness and pain behind your knee. It is commonly seen in women and people aged over 40 (although it can develop at any age).
Baker's cyst, in some cases, does not cause any pain and may go unnoticed. However, you may experience symptoms such as swelling behind your knee and legs, stiffness behind the knees, slight pain in the knee towards the upper calf (especially when you bend your knee or straighten it completely). Pain can become severe when you flex your knee and when you are active. Sometimes the cyst can tear open and the fluid can drain into the tissues of the lower leg, causing swelling and redness.
Baker's cyst is caused by underlying conditions such as rheumatoid arthritis, osteoarthritis and gout, an injury to the knee, or inflammation of the knee joint.
When you present with the above symptoms, your doctor will review your medical history and perform a thorough physical examination of your knee. Further tests such as ultrasound scan and MRI may be recommended in order confirm the diagnosis of Baker's cyst.
Most often, Baker's cyst does not require treatment and may disappear on its own. However, if the cyst is large and causes a lot of pain, the following treatments may be performed:
- Medications: Your doctor injects corticosteroid medications into your knee to reduce pain. However, this doesn't always prevent the reoccurrence of the cyst.
- Fluid drainage: Fluid from your knee is drained using a needle that is guided by ultrasound. Steroid injections sometimes follow fluid drainage to reduce inflammation and pain.
- Physical therapy: Your doctor may suggest the application of ice and a compression wrap or crutches to help reduce the pain and swelling. He/she may also include strengthening and range-of-motion exercises for the muscles around the knee.
- Surgery: Your doctor may treat the underlying cause rather than the condition itself. If a cartilage tear is causing the over production of synovial fluid, surgery may be determined to repair the cartilage.
Depending on your condition, your doctor will determine the best treatment that will help alleviate your symptoms of Baker's cyst.