Shoulder stiffness is a symptom of several common shoulder problems. Unlike shoulder weakness, where patients can have their arm lifted by the examiner (even if the patient can't on his own), a patient with shoulder stiffness has diminished range of motion even when assisted.
What causes shoulder stiffness?
The most common cause of shoulder stiffness is a frozen shoulder, also called adhesive capsulitis. This condition is often misdiagnosed as shoulder bursitis, but can be differentiated with a careful examination. While patients with shoulder bursitis or rotator cuff tears may need help lifting their arm, patients with a frozen shoulder usually cannot get their arm overhead, even with help, and usually cannot reach behind their back.
The other common cause of a stiff shoulder is shoulder arthritis. Shoulder arthritis causes a stiff shoulder by wearing away the normal smooth cartilage surface of the joint, leaving a rough surface. Bone spurs often form as a result of the arthritis and impede the normal motion of the shoulder joint.