Participants were randomly allocated ( 1:1 ) to an intra-articular 1-mL injection of the knee with methylprednisolone acetate ( Depo-Medrol ) , 40 mg/mL , dissolved in 4 mL of lidocaine hydrochloride ( 10 mg/mL ) ( corticosteroid group ) or a 1-mL isotonic saline injection mixed with 4 mL of lidocaine hydrochloride ( 10 mg/mL ) ( placebo group ) .