30 patients with lateral epicondylitis (LE) persisting for a period of more than 6 months and no bilateral involvement were randomly assigned to receive treatment with an injection of either platelet-rich plasma (PRP) or methylprednisolone, a corticosteroid (CS). Both treatments were compared in terms of functional outcomes and ultrasonographic findings involving morphological and vascularization changes observed in the common extensor tendon, when assessed up to 6 months post treatment. The study found that, while both PRP and CS injection resulted in significant improvement in clinical and functional outcomes, at 6 months the PRP group had significantly increased scores for all outcomes except hand grip strength in comparison to the CS group. Additionally, results in the corticosteroid group tended to peak at 3 month,s and then decline at the 6 month evaluation. While the PRP group demonstrated decreased incidence of positive ultrasonographic findings at 6 months, cases of reduced thickness of the common extensor tendon and cortical erosion at the lateral epicondyle increased in the CS group in comparison to pretreatment.