Characteristics of the spreads of platelet-rich plasma (PRP) are not widely known despite commonly use. This study aims to evaluate whether PRP stays within the injected area by using ultrasonography, to improve understanding of the spreads of intratendinous injected PRP. Thirty-nine patients (15 males, 24 females; mean age, 49.3 years), who had symptoms on their elbows (> 6 months) and diagnos...