Sagittal band rupture is a hand injury in which the extensor tendon slips off the knuckle, making it hard to straighten the finger. It affects boxers, martial artists, manual workers and people with conditions such as rheumatoid arthritis. This leaflet explains the injury, outlines modern treatments and shows how to protect long-term hand function.
What is a sagittal band rupture?
The sagittal bands are ribbon-like ligaments encircling each metacarpophalangeal (MCP) joint. Their job is to hold the extensor tendon in the middle of the knuckle and stop it bowstringing. When the radial band tears, the tendon can slide towards the little-finger side, causing pain, swelling and a “popping” sensation as you make a fist.
Why does it happen?
• Direct blow to the knuckle (boxing, rugby, falls).
• Repetitive finger extension (drumming, manual trades).
• Inflammatory disease such as rheumatoid arthritis.
• Connective-tissue disorders (Ehlers-Danlos syndrome).
The middle finger is affected most often because its tendon is under greatest tension when gripping.
Recognising the symptoms
• Sudden pain and swelling over the knuckle.
• Snap or click as the finger bends then straightens.
• Difficulty holding the finger straight without help.
• Tendon visibly slips to one side when making a fist.
Seek urgent assessment if the finger cannot be straightened or if swelling worsens.
How is it diagnosed?
• Careful examination of tendon position during finger movement.
• X-rays to exclude fractures.
• Dynamic ultrasound or MRI for hidden tears or when swelling masks the problem.
Injuries are graded:
Type I – tear without tendon movement; Type II – tendon subluxation; Type III – tendon dislocation.
Treatment options
Non-operative (within six weeks of injury, no open wound):
• Custom yoke splint holding the MCP joint in slight hyper-extension for 4–6 weeks.
• Ice, elevation and anti-inflammatory medication for swelling.
• Early gentle finger exercises within the splint.
Surgical (chronic tears, open injuries, failed splinting, elite athletes):
• Direct repair of the torn band if tissue quality allows.
• Tendon-centralising grafts or slips when primary repair is impossible.
After surgery a protective splint is worn for six weeks, followed by structured hand therapy.
Rehabilitation and recovery timeline
• Weeks 0-4: Controlled movement inside splint, swelling and scar care.
• Weeks 4-6: Splint removed several times daily for active motion; watch for extensor lag.
• Weeks 6-8: Gradual return to normal use, night splint for safety; begin light strengthening.
• Weeks 8-12: Progress to heavier tasks, sports drills, grip work.
• Months 3-6: Full strength and fine control usually restored; heavy combat sports may resume if pain-free.
Preventing future problems
• Wear well-fitted hand wraps or gloves during impact sports.
• Warm up forearm muscles before heavy grip work.
• Treat underlying arthritis promptly to reduce further tendon damage.
• Follow therapist advice on graded loading; avoid “punching through pain”.
Clinical Pearls / Key Points
• Early splinting within six weeks can prevent surgery.
• Radial band tears cause most extensor tendon dislocations.
• Dynamic ultrasound shows real-time tendon snap and is highly sensitive.
• Untreated ruptures can lead to permanent extensor lag and grip weakness.
• Smoking and diabetes delay tendon healing.
Patient FAQs
Why is it called Boxer’s Knuckle?
Because it often follows a gloved-fist impact that forces the tendon sideways at the knuckle.
Can I still move my finger while in a splint?
Yes. Finger joints beyond the splinted knuckle should keep moving to prevent stiffness—your therapist will show safe exercises.
Will the rupture heal on its own?
Minor tears may scar and stabilise, but dislocating tendons rarely stay centred without splinting or surgery.
Is surgery risky?
Complications are uncommon but include stiffness, infection and scar tenderness. Following the rehabilitation plan minimises these risks.
When can I box again?
Light bag work is usually safe after three months; full-contact sparring typically after six months, once grip and punch accuracy match the uninjured side.
Call-to-Action
For specialist assessment or a second opinion on tendon injuries, call 020 3384 5588 or email Info@TheArmDoc.co.uk. For related topics, see our Extensor Tendon Injuries page and Rheumatoid Hand Care guide.Evidence & Guidelines
• British Orthopaedic Association: Management of Closed Extensor Tendon Injuries (2024).• NICE NG211: Rehabilitation After Traumatic Injury (2022).
• British Association of Hand Therapists: Standards of Practice for Extensor Tendon Rehabilitation (2023).
Disclaimer
This leaflet offers general information and should not replace individual medical advice. Always consult a qualified healthcare professional for diagnosis and treatment tailored to your condition.