Radial Tunnel Syndrome is a painful condition of the arm and hand.  It is caused by entrapment of the radial nerve by a number of different potential problems, such as fibrous tissue, abnormal blood vessels and muscles.  As the nerves exit the spinal cord in the neck, its roots form the radial nerve.  The radial nerve runs down the outside of the arm near the elbow before entering the radial tunnel.  The radial tunnel is a path formed by muscle and bone that the nerve passes through.  As it exits the radial tunnel, the nerve passes below the supinator muscle, which is responsible for helping you to twist your arm as if you were using a screwdriver.  The pain of radial tunnel syndrome is constant.  It is worsened by supination of the wrist.  Muscle strength may be weak and it may be difficult to hold objects in your hand.  The pain may radiate up into the upper arm or into the hand.  Radial Tunnel Syndrome may be easily confused with Tennis Elbow, which has similar symptoms.  X-rays and MRIs of the hand and arm may be useful to exclude other causes of pain such as fractures and tumors.  Electromyography and Nerve conduction studies may be useful to determine the exact point of nerve injury and exlcude other causes such as tennis elbow.  The treatment of radial tunnel syndrome begins with conservative modalities such as physical therapy and non-steroidal anti-inflammatory medications.  Injection of the radial nerve with a local anesthetic and a steroid may decrease pain and allow more effective treatment.  Failure of conservative modalities may require surgery to release the nerve from its entrapment.