A joint lease is a rental agreement which has two or more signatories. Often, if there is a dispute or one party wishes to move from the residence early, the party that wants to leave will attempt to get their name removed from the lease. Though this can be difficult, under the right circumstances and with adequate cause, legal liability for a rental can be dissolved.
Ask the other people on the lease if they are willing to accept the additional liability that comes with having your name removed. Often, the landlord will voluntarily allow a new lease to be created with your name absent, but this requires the written permission of your co-tenants.
Attempt to negotiate removal of your name from the lease with your landlord. You may be able to pay a penalty in return for your liability being severed, but this is entirely at the landlord's discretion. However, the fee negotiated will most likely be much less than the remaining balance on your lease, so it is beneficial to go this route if you are willing to pay.
Find a new roommate to replace you, and attempt to get them to take your place on the list. This will almost always require the approval of your roommates, and if they do not accept the change, there is little you can do.
Contact an attorney and discuss with him your legal options in removing your name from the lease. If you can prove illegal or dangerous behavior by one or more of your roommates, you may be able to get your name forcibly removed. In addition, if you can show that the apartment or house is inhabitable, and the landlord has ignored requests to fix the problem, you may also be allowed to terminate the lease early without penalty. This is commonly found with issues of unpaid utility bills that are the landlord's responsibility.
If your landlord agrees to a early-out payment, get it in writing and make sure to get a receipt for the payment.