Randomization and blinding
INFILTRATION, INFILTRATING
A stratified randomization in blocks of four was performed by using a specific software developed by GlaxoSmithKline (C4 Study Design Pack). Each centre was considered as one stratum. Randomized numbers were generated and assigned to participants, which were subsequently allocated to one study group, PRGF or hyaluronic acid. Sealed envelopes were used to conceal treatment allocation until the moment before applying the treatment.Both participants and independent outcome assessors remained blinded to treatment assignment. Clinical researchers were not blinded due to relevant differences between both interventions in terms of appearance and viscosity. As for participants, peripheral blood was drawn from all patients regardless their assigned treatment and the infiltration area was hidden while the injection was given. Outcome assessors were not involved in infiltrating included participants.