Burning pain behind the knee is a common symptom of a Baker's cyst, which is a build-up of fluid behind the knee, states Healthgrades. This fluid is present to lubricate joints and reduce friction. The build-up does not cause any long-term damage to the knee, and many patients experience symptoms coming and going over time. Symptoms may also include inflammation or stiffness.
A Baker's cyst is typically the result of an underlying problem with the knee, such as arthritis or a cartilage tear, explains Mayo Clinic. Treating the underlying cause normally relieves the symptoms. In rare cases, the Baker's cyst bursts and leaks the fluid down into the calf, causing swelling, redness, sharp pain or the sensation of liquid running down the calf. Since the symptoms of a burst are similar to that of a blood clot, it is important to seek medical attention. The doctor may use an X-ray, ultrasound or MRI to confirm the Baker's cyst and rule out other more serious issues.
Injection of a corticosteroid medication may relieve pain and inflammation but does not prevent a recurrence, according to Mayo Clinic. The doctor may also use needle aspiration to drain the fluid from the joint or may recommend physical therapy to strengthen the muscles supporting the knee.