These appearances are typical of rupture of the long head of biceps. The swelling appears when the patient flexes the elbow against resistance and disappears at rest. The rupture may be quite painless and the swelling mistaken for a malignancy. There may be an underlying collagen disorder, eg rheumatoid, but normally occurs in the elderly. Usually no surgical treatment is undertaken as the results are poor and loss of muscle power and mobility is surprisingly minimal.