Posterior Achilles tendon bursitis presents as a painful red mass over the posterior aspect of the heel. So how is an accurate clinical diagnosis made? Bursitis is defined as an acute or chronic inflammation of the bursa. Bursae are sac-like spaces in the connective tissue, closed sacs composed of endothelial cells, lined by synovial membrane with a little synovial fluid. A few are connected to the joints and are located between the bony prominences near the joints and the tendons or muscles and skin. Bursae can be present wherever friction or pressure is high. Many lesions of the joint can cause the disease. Patients often have a history of chronic injuries and occupational history related to the cause of the disease, and there are round or oval bumps with clear margins and varying sizes at the bony prominence near the joint. This can help to confirm the diagnosis.