Baker’s Cyst

The knee is a hinge-type joint comprised of 3 bones (femur, patella, and tibia) surrounded by a soft tissue capsule. Within the joint are two shock-absorbing structures, medial and lateral meniscus. To prevent wear and tear on these structures, small sacks of fluid called bursa are present in areas of pressure or friction. The knee joint is capable of movements of flexion and extension, internal and external rotation. The knee accounts for roughly 40% of all over-use, running-related injuries making it the most common location for such injuries.

What is a Baker’s cyst?
A Baker’s cyst is abnormal swelling of a bursa on the back of the knee. This bursa connects to the knee joint.

What causes Baker’s cysts?
There is no known specific cause for Baker’s cysts, but theories suggest trauma, injury, and arthritis play a role. When the knee produces too much fluid, it can increase the size of the bursa on the back of the knee and lead to a Baker’s cyst.

What are the symptoms of a Baker’s cyst?
Swelling, a stiff feeling behind the knee, and pain are the most common symptoms of a Baker’s cyst. In rare cases, tingling, numbness, or radiating pain down the leg may be present if the cyst is very large. If the cyst ruptures, then symptoms include a sudden onset of pain behind the knee and down the back of the leg.

How is it diagnosed?
A clinical examination of the knee will demonstrate a fullness and swelling behind the knee. X-rays are used to evaluate the knee for arthritis and MRI’s are used to evaluate for the presence of a Baker’s cyst and other knee injuries. An arthrogram, or x-ray after dye is injected into the knee, will demonstrate a pocket of swelling behind the knee – the Baker’s cyst.

How is it treated?
The discomfort of a Baker’s cyst can be treated with a compressive knee brace, anti-inflammatory medications. In some circumstances, the cyst can be drained of fluid. Sometimes cortisone injections are used to reduce inflammation in the knee. Rarely, but sometimes, surgery is needed to remove the cyst. However, surveillance of the cyst is typically safe as they typically do not lead to long-term complications if left alone.

Can I continue to run if I have a Baker’s cyst?
Yes, there are no general restrictions placed on runners who have Baker’s cysts. Let symptoms be the determining factor in running and exercise.

Can Baker’s cysts be prevented?
Because there is no specific cause of Baker’s cysts, there are no specific ways to prevent them from forming.

This information is not intended to diagnose, treat, or prevent any injury or disease. It is intended to serve as an overview of running-related injuries and should not be used as a substitute for sound medical advice from a doctor or therapist.