I do a few tests to determine which side is affected (since no one test alone is reliable): 1) Standing forward bend for ilium (IS joint)- the affected side moves first and furthest. cranially  2) Gillet or standing march for ilium (IS)- the affected PSIS does not drop below S2 or does not move caudally. 3) Usually the extensor hallucus longus (big toe extensor) is weak on the affected side. 4) Ilial spring test: stiff and possibly painful