In 1864, Osborn commanded the 1st Brigade, 1st Division of the XXIV Corps of the Army of the James. Osborn was badly wounded at the Battle of Drewry's Bluff on May 14, 1864, when a musket ball shattered his right elbow and lodged in his arm. He stayed in the hospital until September before being released for duty. In December, he had recovered enough to report for duty. However, he suffered from ankylosis of the injured elbow for the rest of his life.