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.
Sometimes shoulder injuries cause radiating pain in your arm or neck: 1  Arthritis in the joint at the top of your shoulder, called the acromioclavicular joint, can cause radiating pain in the neck. 2 A common cause of acromioclavicular joint arthritis is overuse. Rotator cuff tendonitis can result in pain radiating from the outside of your arm near the topmost part of your shoulder.