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.
Osteoarthritis causes the cushions (cartilage) between your bones (vertebrae) to deteriorate. Your body then forms bone spurs that affect joint motion and cause pain. Nerve compression. Herniated disks or bone spurs in the vertebrae of your neck can press on the nerves branching out from the spinal cord.