A novel Autologous Cytokine-Rich Serum (SARC) to treat knee osteoarthritis patients¿ refractory to a previous glucocorticoid intra-articular injection. A pilot study Cristóbal Orellana; Silvia Garcia Cirera; Albert Rodrigo Parés; Laia Uriel Brotons; Àlex Arqué Corredor; Cristina Aymerich; Rafael Gómez; Anna Carreras; Antoni Berenguer-Llergo; Joan Calvet;