Prolotherapy is still little known in Italy; is an acronym that derives from proliferation therapy (prolo-therapy), coined in the 1950s by G. Hackett, an American orthopedic surgeon. It is a well-established and widespread infiltrative therapy in the United States, especially in the medical-sports field, included in the evidence-based protocols for the treatment of connective tissue diseases (tendinopathies and non-surgical ligament injuries). Prolotherapy is an infiltrative method indicated for tendinopathies, in the forms characterized by tendinosis and is very effective when there are no sub-total or full-thickness ruptures for which the indication is obviously surgical. In cases of tendinosis of any district also associated with partial ruptures, very satisfactory results can be obtained (both from a functional point of view and on pain) and it is also a very valid treatment of instability due to first and second degree injuries of the ligaments.