Thumb and Finger

The thumb is said to account for about half of hand function.

The thumb is formed by three bones and three joints and is an important part of the hand, which is said to account for about half of the function of the hand.

The thumb has greater range of motion than any of the other fingers.

Anatomy of Thumb and Finger

Anatomy of Thumb and Finger

Common Sports Injuries Of The Thumb And Finger

Common Sports Injuries Of The Thumb And Finger
Mallet Finger

Mitsutoshi Hayashi

Doctor of Medicine, specialist in the Japanese Society of Rehabilitation Medicine, specialist in the Japanese Society of Orthopaedic Surgery, specialist in the Japanese Society of Rheumatology, staff to strengthen JOC, and sports physician certified by the Japan Sports Association

Mallet finger often occurs when a ball hits a fingertip in an extended position and stress in the flexion direction is applied to the DIP (distal interphalangeal) joint. Therefore, baseball, softball, volleyball, and other ball sports are common sports in which this injury occurs.

Disease Overview

A deformity in which the DIP joint of the finger cannot be extended completely is called mallet finger. The extensor tendon attached to distal phalange may rupture, occasionally accompanied by an avulsion fracture, deformity of the finger (mallet deformity) or limitation of range of motion when a ball hits the fingertip in the extension position, and stress in the flexion direction is applied to the DIP joint.

Cause and mechanism of onset

Cause of the injury

It is most common in ball sports, such as baseball (often in catchers), softball, basketball (when passing), volleyball (in overhand passing or blocks), and handball. The ball hitting the fingertip directly may cause the injury by adding a stress on the DIP joint. It occurs in a wide range of sports levels from pro to recreation.

Mallet Finger ! Mallet Finger Cause & Onset Figure: DIP joint with stress in the flexion direction may be accompanied by a rupture of the extensor tendon.

Mallet finger 1 Mallet Finger Photo 1 Photo 1: Mallet finger causes typical flexion deformity.

Mallet finger 2 Mallet Finger Photo 2 Photo 2: Mallet finger accompanied by avulsion fracture of the DIP joint


The main symptoms are aching pain, swelling, reddening, and a feeling of warmth at the DIP joint of the finger, and mild tenderness and typical deformity (Photo 1) may occur with avulsion fractures. Make sure to seek medical attention in such cases. Because symptoms of sprains and ligament injuries are similar to those of avulsion fractures, the differential diagnosis is difficult and requires an X-ray check (Photo 2). Treatment and rehabilitation


The DIP joint of the finger is hyperextended with a splint and fixed for 6 weeks. Large pieces of avulsed bone are treated surgically with reduction and fixation (Photo 3).

Mallet finger 3 Mallet Finger Photo 3 Photo 3: An example of surgical fixation of avulsion fracture.


Without adequate period of immobilization, the mallet deformity may persist or recur, making full extension of the fingertip impossible.


The first period: Acute stage (immediately after to 3 weeks after the injury)

First aid should be RICE therapy. In some cases, a cast or splint fixation is used to control pain and swelling. Gentle rehabilitation of the upper extremity, such as a movement of wiping the desk with a towel during fixation, can be done. Lower extremity exercises are permitted soon after the injury.

The second period: Range of motion training (3 to 6 weeks after the injury)

The fixation may be removed after the local rest period ends. Training to expand the range of motion of the finger joints (DIP joint; Proximal interphalangeal (PIP), the second joint; and metacarpophalangeal joint (MP) joint, the third joint) by autokinetic and passive movements, such as lightly grasping clay and pulling a towel, may be then performed gradually.

The third period: Increasing muscle strength (4 to 8 weeks after the injury)

Strengthening (afferent) muscles with a rubber ball may be proactively performed. Change the joints to place the burden by holding a ball with bending or stretching the fingers. Just like tube exercises, use rubber bands to make a stress directly applied to the injured finger and strengthen (afferent and efferent) the muscles. Also, dorsiflexion and palmar flexion of the wrist joint may be performed to strengthen joint movement around the wrist.

The fourth period: Return to sports (8 to 12 weeks after the injury)

Restart passing practice gradually. Training, such as thumb push-ups, may be performed without impact but with strong stress on the fingers. To return to sports, athletic tape may be used proactively to prevent recurrence and to help patients feel psychologically secured.

Extra edition: It's just a sprained finger, but it's still a big deal.

A sprained finger is a generic term generally representing finger injuries. It includes a variety of conditions, ranging from mild injuries such as bruises and sprains to ligamentous injuries and to avulsion fractures and dislocations. Therefore, treatment may take 2 to 3 days or several months. It is recommended to seek medical attention in the following cases: swelling, severe pain, deformation, bruising, weakness, inability of gripping, and slow healing. Finger disorders tend to be neglected in sports settings, but caution should be exercised because they may simply be viewed as sprained fingers and may exclude appropriate initial measure (treatment) or are required to return too early before complete healing. The sprained finger is very serious injury.

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