Sciatica refers to back pain caused by a problem with the sciatic nerve. This is a large nerve that runs from the lower back down the back of each leg. When something injures or puts pressure on the sciatic nerve, it can cause pain in the lower back that spreads to the hip, buttocks, and leg.
Osteoarthritis of the shoulder is a gradual wearing of the articular cartilage that leads to pain and stiffness. As the joint surface degenerates, the subchondral bone remodels, losing its sphericity and congruity. The joint capsule also becomes thickened, leading to further loss of shoulder rotation.
What causes the pain we feel from osteoarthritis is the question we'll address now. Osteoarthritis pain likely comes from other structures within the affected joint that undergo change when cartilage becomes worn away. While the cartilage may not have nerve endings, the surrounding structures do.