ischi-, ischio- +

(Greek: hip, hip-joint, hip-bone; haunch)

ischialgia
1. Pain in the hip; specifically, the ischium; also, ischiodynia.
2. A rarely used term for sciatica; also known as: ischioneuralgia.
ischiectomy
Surgical removal or excision of the ischium (the inferior dorsal portion of the os coxae (hip bone); it is a separate bone in early life).
ischiodidymus
Symmetrical conjoined twins united at the pelvis.
ischiodynia
Pain in the hip; specifically, the ischium (seat bone of the pelvis).
ischioneuralgia
1. Pain in the hip; specifically, the ischium or the lower part of the hip.
2. A rarely used term for sciatica.

Sciatica refers to a syndrome characterized by pain radiating from the back into the buttock and into the lower extremity along its posterior or lateral aspect and most commonly caused by prolapse of the intervertebral disk. The term is also used to refer to pain anywhere along the course of the sciatic (referring to the hip) nerve.

ischionitis
Inflammation of the ischium or lower hip.
ischiopagus
Conjoined twins fused at the ischia, the axes of the two bodies extending in a straight line but in opposite directions; according to the number of lower limbs shared, classified as bipus, tripus, and tetrapus.
ischium (s), ischia (pl)
The lower section, or part, of the hip bone.

Ischium is the bone which forms the lower and back part of the pelvis. It bears the weight of the body when sitting.

os ischia
Hip joint.