Unilateral Nutation Unilateral sacral nutations are nonphysiological dysfunctions of the sacroiliac (SI) joint. While bilateral restriction of nutation, either anterior or posterior, can also occur, it is not commonly seen. If the facet joints at L5-S1 are free to bilaterally open and close, then L5 demonstrates adaptive mechanics by following the sacrum in flexion/extension and moving in the opposite direction in a neutral position.

Anteriorly Nutated Sacrum on the Left -- L5 Adaptive
A unilateral anterior nutation of the sacrum on the left results from an inability of the left sacral base to move superiorly and to nutate posteriorly. In the neutral position, the sacrum is side bent left and rotated right because the left sacral base has moved inferiorly and anteriorly. When lumbar flexion is introduced, asymmetry of the inferior lateral angles (ILAs) inceases. When lumbar extension is introduced, ILA symmetry improves, but never becomes symmetrical.

• In the neutral position, with the sacrum side bent left and rotated right, L5 is considered to be adaptive (i.e., no ERS dysfunctions) if it remains level and appears to rotate to the left. Click here to visualize a unilateral anterior nutation of the sacrum on the left with the patient in the neutral position -- L5 adaptive).
• In the forward bent position, with the sacrum more side bent left and rotated right, L5 is considered to be adaptive if it appears rotated to the right as it follows the right rotated sacral base. Click here to visualize a unilateral anterior nutation of the sacrum on the left with the patient in the forward bent position -- L5 adaptive).

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Anteriorly Nutated Sacrum on the Left -- L5 NonAdaptive (ERSleft)
Non-neutral dysfunctions at L5 (ERSleft) often accompany an anteriorly nutated sacrum on the left. An ERSleft at L5 can be identified when the patient is forward bent and L5 appears rotated left when compared to a right rotated and left sidebent sacrum.

• In the neutral position, with the sacrum side bent left and rotated right, L5 is considered to be nonadaptive if it remains level and is not rotated to the left. Click here to visualize a unilateral anterior nutation of the sacrum on the left with the patient in the neutral position -- L5 nonadaptive).
• In the forward bent position, with the sacrum more side bent left and rotated right, L5 is considered to be nonadaptive if it remains level and is not rotated to the right. Click here to visualize a unilateral anterior nutation of the sacrum on the left with the patient in the forward bent position -- L5 nonadaptive).

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Posteriorly Nutated Sacrum on the Right -- L5 Adaptive
A unilateral posterior nutation of the sacrum on the right results from an inability of the right sacral base to move inferiorly and to nutate anteriorly. In the neutral position, the sacrum is side bent left and rotated right because the right sacral base has moved superiorly and posteriorly. When lumbar extension is introduced, asymmetry of the inferior lateral angles (ILAs) inceases. When lumbar flexion is introduced, ILA symmetry improves.

• In the neutral position, with the sacrum side bent left and rotated right, L5 is considered to be adaptive (i.e., no FRS dysfunctions) if it remains level and appears to be rotated to the left. Click here to visualize a unilateral posterior nutation of the sacrum on the right with the patient in the neutral position -- L5 adaptive).
• In the backward bent position, with the sacrum more side bent left and rotated right, L5 is considered to be adaptive if it appears rotated to the right as it follows the right rotated sacral base. Click here to visualize a unilateral posterior nutation of the sacrum on the right with the patient in the backward bent position -- L5 adaptive).

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Posteriorly Nutated Sacrum on the Right -- L5 NonAdaptive (FRSright)
Non-neutral dysfunctions at L5 (FRSright) often accompany a posteriorly nutated sacrum on the right. An FRSright at L5 can be identified when the patient is backward bent and L5 appears more rotated right when compared to a right rotated and left sidebent sacrum.

• In the neutral position, with the sacrum side bent left and rotated right, L5 is considered to be nonadaptive if it remains level and appears to be rotated to the right. Click here to visualize a unilateral posterior nutation of the sacrum on the right with the patient in the neutral position -- L5 nonadaptive).
• In the backward bent position, with the sacrum more side bent left and rotated right, L5 is considered to be nonadaptive if it appears more rotated to the right than the right rotated sacral base. Click here to visualize a unilateral posterior nutation of the sacrum on the right with the patient in the backward bent position -- L5 nonadaptive).

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