the last segment of the spine is the
sacrum the sacrum attaches to the large
pelvic bones known as the ilium the
joints that connect the sacrum to the
ilium are called the sacroiliac joints
or SI joints the integrity of the SI
joint depends on strong ligaments that
encase and cover the joint these
ligaments compress and stabilize the
joint SI joint pain can develop when
these ligaments become damaged or
degenerate due to age allowing the joint
to have excessive motion this excessive
motion may inflame and disrupt the joint
and surrounding nerves pain commonly
presents in the lower back above one or
both of the posterior superior iliac
spine also known as the PSIs in addition
to the lower back pain symptoms may
present in the buttocks and thighs
because SI joint pain can produce
sciatica like symptoms it is very
important to include the SI joint in a
comprehensive differential diagnosis of
low back pain to confirm the correct
pain generator is identified