Boxers Knuckle

What is Boxers Knuckle

• Boxers knuckle is an injury to an extensor tendon. The extensor tendons are located on the back of the hand. They help the fingers to extend. They also help to protect the finger bones and joints.
• Boxers knuckle develops if the layer of tissue that lies over these tendons becomes damaged and causes a tendon to move out of position. Boxer’s knuckle often affects the first knuckle of the middle finger.
• It is not surprising that given the tremendous forces placed on a boxer’s clenched fist when throwing a punch that traumatic injury can occur.
• Along with fractures of the metacarpals and phalanges, carpal boss and boxer’s knuckle are the most common hand injuries of boxers seen in clinical practice.
• Boxer’s knuckle is characterized by localized tenderness and sharp pain over metacarpophalangeal joints with subluxation or dislocation of the longitudinal central tendon leading to rupture of the extensor hood mechanism and associated longitudinal central tendon dysfunction.
• Along with the sagittal bands, the longitudinal central tendon serves as a shock absorber that protects the underlying articular capsule and surfaces. When these structures are damaged by the trauma of a punch, the central tendon subluxes or dislocates, leaving the underlying joint unprotected

What are the causes?

Boxers Knuckle is caused by direct or repeated injury (trauma) to a knuckle. If often happens during activities such boxing or martial arts.

What increases the risk of Boxers Knuckle?

This condition is more likely to develop in:

• People who participate in hitting or fighting sports, such as boxing and martial arts.
• People who play contact sports, such as football and rugby.
• People who have poor strength and flexibility.
• People who have injured a knuckle.

What are the symptoms of Boxers Knuckle?

Symptoms of this condition include:

• Pain and swelling over the injured knuckle.
• Difficulty straightening the affected finger.
• Delay when you try to straighten the affected finger.
• Tenderness when you touch the injured knuckle.
• Abnormal movement of the affected tendon when you open and close your hand.

On physical examination, the patient with boxer’s knuckle will exhibit swelling over the affected joint with a decreased range of motion.

The examiner may detect lag of extension of the affected digit in contrast to the adjacent untraumatized fingers. The pain associated with boxer’s knuckle can be reproduced by applying pressure to the affected knuckle and by active flexion and extension.

Patients with boxer’s knuckle often demonstrate ulnar deviation of the central tendon. With acute trauma to the dorsum of the hand, ecchymosis over the affected joint or joints may be present.

How is this diagnosed?

• Boxers Knuckle is diagnosed with a physical exam. Sometimes, X-rays are taken to check for additional problems, such as a fracture or cyst in the bone under the injured area.
• Plain radiographs are indicated in all patients with boxer’s knuckle to rule out fractures and identify subchondral cysts, which are often associated with osteochondral fracture.
• Based on the patient’s clinical presentation, additional testing may be warranted to rule out inflammatory arthritis, including a complete blood count, erythrocyte sedimentation rate, uric acid level, and antinuclear antibody testing.
• Magnetic resonance imaging (MRI) and ultrasound imaging of the fingers and wrist are indicated to confirm the diagnosis and if joint instability, occult mass, occult fracture, infection, or tumor is suspected. Radionuclide bone scanning may be useful to identify stress fractures.

Differential Diagnosis

• The tentative diagnosis of boxer’s knuckle is made on clinical grounds and confirmed by radiographic testing.
• Arthritis, tenosynovitis, or gout of the affected digits may accompany boxer’s knuckle and exacerbate the patient’s pain.
• Occult fractures occasionally confuse the clinical presentation.

How is Boxers Knuckle treated?

Boxers Knuckle may be treated with:

• Ice applied to the affected area.
• Medicines for pain.
• Placing the hand in a cast or splint to keep the injured joint from moving while the tendon heals.
• Surgery to repair the injured tendon or tissue. This may be done in severe cases.

Initial treatment of the pain and functional disability associated with boxer’s knuckle consists of nonsteroidal antiinflammatory drugs (NSAIDs), simple analgesics, or cyclooxygenase-2 (COX-2) inhibitors.

Physical modalities, including local heat and gentle range-of-motion exercises, should be introduced to avoid loss of function.

Vigorous exercises should be avoided, because they will exacerbate the patient’s symptoms.

A nighttime splint to protect the fingers may be helpful. If sleep disturbance is present, low-dose tricyclic antidepressants are indicated. Ultimately, surgical repair is required to alleviate the patient’s pain and functional disability.

Follow these instructions at home:

If you have a cast:

• Do not stick anything inside the cast to scratch your skin. Doing that increases your risk of infection.
• Check the skin around the cast every day. Report any concerns to your health care provider. You may put lotion on dry skin around the edges of the cast. Do not apply lotion to the skin underneath the cast.
• Keep the cast clean and dry.

If you have a splint:

• Wear it as told by your health care provider. Remove it only as told by your health care provider.
• Loosen the splint if your fingers become numb and tingle, or if they turn cold and blue.
• Keep the splint clean and dry.

Bathing

• Do not take baths, swim, or use a hot tub until your health care provider approves. Ask your health care provider if you can take showers. You may only be allowed to take sponge baths for bathing.
• If your health care provider approves bathing and showering, cover the cast or splint with a watertight plastic bag to protect it from water. Do not let the cast or splint get wet.

Managing pain, stiffness, and swelling

• If directed, apply ice to the injured area.
  • Put ice in a plastic bag.
  • Place a towel between your skin and the bag.
  • Leave the ice on for 20 minutes, 2–3 times per day.

Driving

• Do not drive or operate heavy machinery while taking prescription pain medicine.
• Ask your health care provider when it is safe to drive if you have a cast or splint on your hand.

General instructions

• Do not put pressure on any part of the cast or splint until it is fully hardened. This may take several hours.
• Do not use any tobacco products, including cigarettes, chewing tobacco, or e-cigarettes. Tobacco can delay bone healing. If you need help quitting, ask your health care provider.
• Take over-the-counter and prescription medicines only as told by your health care provider.
• Keep all follow-up visits as told by your health care provider. This is important.

Contact a health care provider if:

• Your pain gets worse.
• You hand tingles or feels numb.
• Your hand becomes discolored.

What are the complications of Boxers Knuckle

• The clinician should always keep in mind that occult fracture or tumor may mimic the clinical symptoms of boxer’s knuckle.
• Radiographic imaging is important to avoid misdiagnosis.
• Given the amount of trauma sustained with the sport of boxing, coexistent arthritis is usually present.

Summary

• Sagittal band rupture is often referred to as a “Boxer’s knuckle”. This lesion, which is common in boxers, occurs often after clenched-fist trauma and mostly at the third MCP.
• Clinical findings of Boxers Knuckle consist of pain, swelling, incomplete joint extension, and subluxation of the extensor tendon.
• Sagittal bands are transversely located ligaments, centralizing the extensor tendon.
• Due to ulnar deviation predisposition of the MCP joint and anatomic weakness, the radial band ruptures more often than ulnar sagittal bands.
• Abnormal signal intensity or echogenicity of the thickened and possible discontinuity of the sagittal band with edema of the dorsal soft tissues suggest the diagnosis on MRI and ultrasound.
• Dynamic ultrasound (US) can confirm the extensor tendon subluxation during MCP joint flexion, which is an advantage compared to static MRI.
• Conservative treatment can be considered in acute cases, while surgical repair of the sagittal bands is standard of care in severe acute and chronic ruptures.