Rheumatoid arthritis can cause numbness.
According to the Center for Disease Control, nearly 50 million Americans have been diagnosed with arthritis.  This diagnosis covers a broad range of joint diseases including rheumatic conditions, which also affect connective tissues.
The Difference between Osteoarthritis and Rheumatoid Arthritis
The breakdown of cartilage around a joint causes osteoarthritis. Since cartilage acts as a cushion for the joint, this breakdown causes a considerable amount of pain. However, osteoarthritis is localized to one or two joints.
Rheumatoid Arthritis is classified as an autoimmune disease. It not only causes damage to the joint but also attacks the surrounding connective tissue, such as ligaments and tendons.
Does Arthritis Cause Numbness?
Osteoarthritis rarely causes numbness. However, if you have been diagnosed with rheumatoid arthritis, you may also suffer from numbness in your hands or feet. This is caused by inflammation of the connective tissues, which exert pressure on the nerve. If left untreated, this pressure can cause permanent nerve damage. 
The numbness caused by rheumatoid arthritis has a bilateral effect. This means that both of your hands or both of your feet will be affected. It is also characterized by swollen joints that feel warm to the touch. The most common areas that are affected are the wrists, fingers, knees, ankles and feet. 
Pattern of Numbness and Tingling
Most people who suffer from the numbness associated with rheumatoid arthritis report that it is the most severe when they first get up in the morning. Once they get moving; the stiffness and numbness begin to subside. Morning stiffness and numbness often have nothing to do with your sleeping posture. It is caused by inflammation that builds up as you sleep.
Constant, repetitive motion, such as typing on a keyboard can also cause inflammation. When this happens, you may experience numbness throughout the day.
Is Numbness Caused by Arthritis Serious?
Pain is usually the first indication of nerve damage. Numbness or tingling is the second indication and should never be ignored. Numbness that persists throughout the day is serious and should be attended to as soon as possible.
 Centers for Disease Control and Prevention
Arthritis-Frequently Asked Question-General Public
10 Serious Rheumatoid Arthritis Symptoms to Never Ignore
 New York Times