The L4-L5 motion segment is characterized with the following more common injuries and disorders:
- Facet joint problems. The L4-L5 motion segment with its high mobility is susceptible to the disorders associated with the facet joints, such as osteoarthritis, synovial cyst (fluid-filled sac) formation, and facet instability.
- Disc problems. Disc degeneration is a wide spread complication for the L4-L5 segment. This condition is likely to arise from the excessive loads at the L4-L5 motion segment and insufficient mobility in the segments below. Degeneration-induced change in disc height could damage the lordosis of the lumbar spine. Degeneration or injury could cause a hernia (90%-95% of all herniated discs occur in the segments where l4 l5 and s1 are located).A bulging disc is typical for the first stage of future protrusion/ herniation.
- Spondylolysis. Pars interarticularis (a small segment of bone from the vertebral arch joining the facet joints) is likely to fracture at the L4-L5 level because of the focused compressive loads in this region. It can happen on one or both sides.
- Degenerative spondylolisthesis. The L4-L5 facet joint changes are age driven, which makes it vulnerable to spondylolisthesis (forward slippage of L4 on L5) because of degenerative changes.
- Spinal stenosis. Narrowing (stenosis) of bony openings for nerves due to the bone spurs (atypical bone growth) or other degenerative changes is likely to result in compression of the nerve roots in the region of stenosis.
Outer trauma, including falls or motor vehicle accidents, may be the cause of facet joint dislocation, fracture, and/or damage to the cauda equina. The L4-L5 vertebrae and spinal segment rarely suffer from tumors and infections.