Injuries from rusty nails piercing the finger may cause infection of the synovial sheath of the finger. When the tendon and synovial sheath become inflamed (tenosynovitis), the finger may swell and become painful with movement. Since the tendons of the 2nd, 3rd, and 4th fingers almost always have their own synovial sheaths, the infection is usually confined to the infected finger. However, if the infection is left untreated, the proximal measurement of these synovial sheaths may rupture and cause the infection to spread to the central palmar space. Because the synovial sheath of the little finger is usually attached to the common flexor sheath, if tenosynovitis occurs in the little finger, infection may spread to the common flexor sheath and then to the anterior forearm via the palmar and carpal tunnels, in the space between the anterior rotator and flexor group tendons. Similarly, tenosynovitis of the thumb may spread proximally through the synovial sheath of the flexor digitorum longus tendon, and how far the infection spreads from the fingers depends on the differences in their connection to the common flexor sheath. The tendons of the abductor pollicis longus and extensor pollicis brevis are located in the same musculocutaneous sheath on the back of the wrist. Tendons in a common sheath can lead to fibrous thickening of the synovial sheath and narrowing of the bony fibrous tunnel. Excessive friction is caused by repetitive force on the hand during clenching and wringing (e.g., wringing clothes), a condition known as Quervain’s tenosynovitis stenosis (commonly known as mama’s hand). It causes a painful sensation in the wrist that spreads proximally and distally to the fibrous sheath of the forearm and thumb on the lateral side of the wrist, where localized tenderness can be felt. Thickening of the fibrous sheath on the lateral side of the palm of the finger can result in narrowing of the fibrous tunnel of the bone. This narrowing is caused by repetitive use of the finger. If the tendons of the flexor digitorum profundus and flexor digitorum superficialis become enlarged near the tunnel, the patient will be unable to extend the finger. When the finger is passively extended, a snapping sound can be heard. When the enlarged tendon moves and produces a flexion movement, an additional snapping sound will be heard, and this condition is called tenosynovitis stenosis of the finger (commonly referred to as pancreatic finger). Diagnosis 1.Mother’s hand (1) pain when the thumb is bent backward with force and external exhibition; (2) pain when the thumb is held inside the fist and the fist is moved toward the ulna; (3) pain when the radial styloid is touched. 2.Plank finger (1) The pain may occur at the joint between the metacarpal and phalanges; (2) The finger is often stuck in a flexed position; (3) Passive force is usually required to straighten the finger. Treatment 1.Mother’s hand For the tendon do ultrasound, deep massage 1~2 weeks, 3~4 times a week treatment. Maintain or improve the mobility and inflammation of the tendon. If the inflammation is serious, you can consider wearing a parapod to avoid increasing the number of friction. 2.Plank finger can be fixed in a straight position at night before going to bed with a patch or wearing a parapod. Rehabilitation exercises of finger flexion and tendon sliding should be performed every hour during the day. Ultrasound, soft tissue release, and ice can be used to reduce pain and swelling.