Arnold (groin) was listed as a limited practice participant on Thursday's injury report.
Arnold was not listed on Wednesday's estimated walk-through practice, but a groin injury prevented the rookie first-round pick from participating in all team drills Thursday. Arnold would likely avoid an injury designation heading into Sunday's game against the Colts if he's able to practice in full Friday. Over the six regular-season games since the Lions' Week 5 bye, Arnold has tallied 22 tackles (15 solo), three pass defenses and one fumble recovery.