An extensor tendon injury of the hand can make simple movements like straightening your finger or thumb difficult. These tendons lie just beneath the skin on the back of your hand and are vulnerable to cuts, jams, and crushing injuries. Early recognition and proper treatment are essential for restoring full function and preventing chronic deformities.
The extensor tendons connect the forearm muscles to the bones of the fingers and thumb. They work together to straighten the digits and help position the hand for gripping and releasing objects. Unlike flexor tendons, which are deeper and protected by tunnels, the extensor tendons are thin and close to the surface, so even a minor laceration can interrupt their function.
An extensor tendon injury of the hand often results from a cut, a jammed finger, or a crushing force. The injury can be as simple as a small cut on the knuckle or as complex as a fracture combined with tendon damage. Athletes, factory workers, and people doing household tasks are all at risk.
For example, a basketball player who catches the ball awkwardly on the fingertip may develop a mallet finger. A carpenter who hits the dorsal side of the hand with a tool may sustain a laceration over the middle phalanx. These scenarios require different treatment plans, but both are forms of extensor tendon injury of the hand.
Doctors classify extensor tendon injuries by their location using a zone system. The zone matters because it affects the risk of joint involvement, infection, and how well the tendon can heal. The extensor zones are numbered from the fingertip to the forearm, with different patterns in the thumb.
| Zone | Location | Typical presentation |
|---|---|---|
| Zone I | Distal interphalangeal (DIP) joint | Drooping fingertip, mallet finger |
| Zone II | Middle phalanx | Laceration or crush over the middle bone |
| Zone III | Proximal interphalangeal (PIP) joint | Boutonniere deformity |
| Zone IV | Proximal phalanx | Cut or blunt injury over the finger |
| Zone V | Metacarpophalangeal (MCP) joint | Fight bite injury over the knuckle |
| Zone VI | Dorsal hand | Difficulty extending multiple fingers |
| Zone VII | Wrist | Tendon injury under the retinaculum |
| Zone VIII | Distal forearm | Muscle-tendon junction injury |
The symptoms of an extensor tendon injury of the hand depend on which tendon is affected and how severe the damage is. Pain is common, but the most reliable sign is the inability to actively straighten the finger or thumb.
A doctor will start by asking how the injury happened and then examine the hand carefully. The examination is simple but requires attention to every joint. They will ask you to straighten each finger segment against resistance, and they will look for wounds that may have reached the tendon.
In some cases, ultrasound or MRI may help if the tendon injury is not obvious on examination. However, most extensor tendon injuries of the hand can be diagnosed with a focused physical exam and X-rays.
Treatment depends on the zone, the size of the tear, and whether there is a wound or fracture. The main goal is to restore the tendon’s ability to glide while protecting the healing tissue.
Many closed extensor tendon injuries can be treated with splinting alone. This is often the case for mallet finger, where the tendon is torn but the skin is intact. The fingertip is held straight until the tendon heals.
Surgery is needed when the tendon is completely cut, when the injury involves a fracture, or when non-surgical treatment fails. The surgeon will reattach the tendon ends and may use a suture anchor if the tendon pulled off the bone.
If you cannot actively straighten the fingertip after a minor jam, do not assume it is just a sprain. An extensor tendon injury of the hand can look mild but still require splinting.
Recovery from an extensor tendon injury of the hand is guided by a structured rehabilitation plan. The exact timeline depends on the severity and the repair technique. Modern protocols favor early controlled motion rather than prolonged stiffness, but this only applies when the tendon repair is stable.
Your hand therapist may teach you specific exercises for the affected finger joint. For mallet finger, you might be taught to support the fingertip while moving the middle joint. For boutonniere injury, the focus is on preserving the middle joint’s straight position while allowing the fingertip to bend.
Healing from an extensor tendon injury of the hand depends as much on protected movement as it does on the initial repair. Splinting is not optional.
Without proper care, some patients develop stiffness, weakness, or a permanent deformity. Infections are especially dangerous when a bite or dirty wound caused the injury. Adhesions, or scar tissue that binds the tendon, can limit gliding and make movement difficult.
Not every injury can be prevented, but certain habits reduce the risk of an extensor tendon injury of the hand. Athletes should learn safe catching techniques, and workers should use appropriate hand protection.
An extensor tendon injury of the hand can be simple or complex, but early diagnosis and correct treatment make a major difference. Whether the injury is a jammed fingertip or a deep cut, the key is to protect the tendon while encouraging controlled movement. If you suspect an injury, see a skilled hand therapist or orthopedic provider quickly. With the right splinting, surgery, and rehabilitation, most people regain good function and avoid lasting deformity.
The most common is mallet finger, which occurs at the DIP joint when the fingertip can no longer straighten. It often results from jamming the fingertip against a ball or a hard object.
Most isolated extensor tendon injuries require continuous splinting for four to six weeks. After that, night splinting may continue for another two to four weeks. Your doctor will adjust this based on healing and joint movement.
Sometimes you can still move the finger partially because other tendons help with extension. However, the joint controlled by the injured tendon will usually droop or lag behind. Active testing by a professional is necessary to detect the weakness.
Surgery is needed for partial tears that do not respond to splinting, complete tendon cuts, fractures with displacement, and injuries with joint involvement. It is also needed when there is a wound that must be cleaned and closed.
A mallet finger is a detachment or tear of the extensor tendon at the fingertip. The tip bends downward while the rest of the finger remains straight. Most cases are treated with a splint.
A boutonniere deformity happens when the central slip of the extensor tendon tears at the PIP joint. The middle joint bends inward while the fingertip points upward. It can be serious if not treated early with splinting or surgery.
Yes. Many closed injuries, especially mallet finger, heal with continuous splinting. The tendon ends do not need to be stitched if they are close together and the joint is held in the correct position.
The tendon may heal in a shortened position, causing a fixed deformity like mallet finger or boutonniere. Over time, joint stiffness and arthritis can develop, making treatment much harder.
Return to sports usually takes two to three months after an uncomplicated injury. Contact sports and heavy gripping activities require full strength and a protective splint. Your therapist should guide this transition.
Gentle active and passive range-of-motion exercises are the core of rehabilitation. A hand therapist may prescribe isolated tendon-gliding exercises, joint blocking, and later resistance exercises with putty or bands. Follow the plan carefully to avoid re-injury.
