How long would it take to get back full range of motion after acl reconstructive surgery?

Can take weeks: Maintaining full knee extension is far more important after acl surgery. Flexion usually advances toward normal over the first 1-3 wks. Full flexion, however, may take more than a month as any residual significant swelling will make absolute full flexion difficult to regain until the swelling completely resolves. Concomitant meniscal repair may purposefully limit flexion to 90 degrees for 6 weeks.