<P> The sacroiliac joint or SI joint ( SIJ ) is the joint between the sacrum and the ilium bones of the pelvis , which are connected by strong ligaments . In humans , the sacrum supports the spine and is supported in turn by an ilium on each side . The joint is strong , supporting the entire weight of the upper body . It is a synovial plane joint with irregular elevations and depressions that produce interlocking of the two bones . The human body has two sacroiliac joints , one on the left and one on the right , that often match each other but are highly variable from person to person . </P>
<P> The sacroiliac joint or SI joint ( SIJ ) is the joint between the sacrum and the ilium bones of the pelvis , which are connected by strong ligaments . In humans , the sacrum supports the spine and is supported in turn by an ilium on each side . The joint is strong , supporting the entire weight of the upper body . It is a synovial plane joint with irregular elevations and depressions that produce interlocking of the two bones . The human body has two sacroiliac joints , one on the left and one on the right , that often match each other but are highly variable from person to person . </P>
what kind of joint is the si joint
what kind of joint is the si joint
a synovial plane joint
a synovial plane joint