Outer part of the elbow (lateral epicondyle) where tennis elbow occurs Tennis elbow Tennis elbow or lateral epicondylitis is a chronic or an acute inflammation of the tendons that arise from the outer part of the elbow. The affected tendons are the tendons of extensor muscles which originate from the lateral epicondyle of humerus. It is caused by the repetitive movements and overuse. It damages the tendons which results in pain and tenderness on the outer part of the elbow. De Quervain's syndrome De Quervain's syndrome is a medical condition when the synovial sheath surrounding tendons in the first extensor tendon<unk>  becomes inflamed, so called tenosynovitis. The tendons of the abductor pollicis longus and the extensor pollicis brevis run narrower due to the thickening of the synovial sheath, which causes pain when extending and moving the thumb outward. Fourth<unk>  syndrome The presence of an additional tendon may result in a condition called fourth<unk>  syndrome. Supernumerary tendons are common in the fourth extensor tendon<unk> . Supernumerary tendons can refer to the additional tendons of normal structures or tendons of rare anatomical variants such as the extensor medii proprius or the extensor digitorum brevis manus. The increased pressure in the synovial sheath is known to directly or indirectly compress the<unk>  interosseous nerve of radial nerve. Also, the extra pressure causes synovitis which results in pain in the dorsal part of the wrist. Misdiagnosis of rare anatomical variants Anatomical variants are often encountered in the extensor<unk>  of the<unk> . Clinical expressions of the extensor digitorum brevis manus are often mistaken for a ganglion, cyst or tumour.
Posterior compartment of the forearm
Ulnar claw
Seal finger
Finger cot
Boot 
Distal radioulnar articulation
Pelvic digit
Abductor wedge