Posterior bursitis of the Achilles tendon presents as a painful red lump on the upper back of the heel. The following are the differential diagnosis of posterior Achilles tendon bursitis. 1.Acute bursitis Acute bursitis is characterized by pain, limited tenderness and limited activity. If the superficial bursa is involved (prepatellar and hawksbill), the localization is often red and swollen, chemical or bacterial bursitis have severe pain, the attack can last for days to weeks, and recur many times. 2.Chronic bursitis Chronic bursitis develops after multiple episodes of acute bursitis or repeated trauma. Due to the proliferation of the synovial membrane, the wall of the bursa becomes thickened and the bursa eventually adheres. Due to pain, swelling and tenderness, it can lead to muscle atrophy and activity limitation. 3.Subacromial bursitis Subacromial bursitis manifests as limited pain and tenderness in the shoulder. Especially when abduction is 50°~130°, it is more obvious. Injurious bursitis Injurious bursitis is more common and is chronic. Injurious bursitis is more common and chronic. It is often caused by prolonged and repeated friction and compression in the prominent part of bone structure, and it is often caused by a sudden burst on the basis of chronic bursitis, which can be accompanied by bloody synovial exudation when the force of injury is large. 5.Infectious bursitis Infectious bursitis can cause purulent bursitis due to pathogenic bacteria brought by infected foci, and can cause cellulitis in the surrounding tissues, and the sinus tracts often remain after the rupture. 6, gouty bursitis gouty bursitis is likely to occur in the eagle’s beak and prepatellar bursa, the bursa wall can be chronic inflammatory changes, and there are lime-like sediment deposits. Patients tend to have a history of chronic injury and occupational history associated with the causation of the disease. The bony prominences near the joints are characterized by round or oval shaped lumps of varying size with clear margins. Pain and tenderness are obvious in acute cases, but less so in chronic cases, and the affected limbs may have different degrees of impaired mobility. If secondary infection, there may be redness, swelling, heat and pain.