As well as old leases, you should keep anything that documents the landlord-tenant relationship or supports the items you report on your tax return. If the IRS audits your tax return and you cannot produce the correct verification documents, you may be liable for additional tax and penalties.
The facet joints link the vertebrae together and give them the flexibility to move against each other. The facets are the bony knobs that meet between each vertebra. There are two facet joints between each pair of vertebrae, one on each side.
Plus the entire pelvic bone moves forward in space. This set of deviations from the ideal alignment of the body tends to lock the knees back (called hyperextension.) Another thing you can see in a swayback posture (as long as you're viewing it from the side,) is a backward movement of the entire thoracic spine.