Im trying to do the alteration ritual quest. I am told to go to High Gate Ruins to retrieve Kavozheins fang. Unfortunately I had previously cleared High Gate ruins. When I get to Vokuns throne room the gates on both sides are closed with no way to open them. WHat I need is one the other side of those gates near the word wall.

Its basically the most frustrating thing I have encountered in Skyrim. Just because I cleared out a dungeon already its breaks a quest later? Gates that won't open? WHY?!!

Bump. So No one knows or has encountered this issue? Gates are locked with no way (that I know of) to open them. Kavozheins fang is on the other side of the locked gate. Its ridiculous!

There may be a workaround to get back in there, if you have a follower and whirlwind sprint shout.

Look at thehttp://www.uesp.net/wiki/Skyrim:High_Gate_Ruinshttp://www.uesp.net/wiki/Skyrim_talk:High_Gate_Ruinshttp://www.uesp.net/wiki/Skyrim:High_Gate_Ruinsof this page for details.
Good luck

I thought I could be of help but I realized I found the fang in a different dungeon (Volskygge).

And there's your possible answer: reload from prior to getting the quest until the darn thing is located in one of the other five locations.
Yes, it's annoying, but it would do the job. Just as using Whirlwind Sprint and a Follower would, as Merari suggested.

If you're on a PC you can just open up the console and type in "TCL" to fly through walls. Repeat to turn it off.

Take the back door...i mean,enter from the back exit of the dungeon....from the wikia....But it is still possible to enter the back of the Thone Room, if that is required in later Quests. You will then have to use the back entrance to the Vokun′s Throne room. And you have to have a http://elderscrolls.wikia.com/wiki/Follower with you. Climb on top off the ruins on the right side in the second room of High Gate Ruins (right side on the map of High Gate Ruins where the door to Vokun's Throne Room is on the left side). Climb as high as you can get, to be about the same height as the platform on the opposite side. Then use http://elderscrolls.wikia.com/wiki/Whirlwind_Sprint to get on to the platform. Now wait by the gate and you Follower should come to the other side of the gate. Then ask him or her to pull the chain with "Talk to ..." and "I need you to do something."