Medically Reviewed | Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle, Michigan
Quick Answer:
Quick Answer: A subungual hematoma is a collection of blood beneath the toenail following trauma or repetitive pressure (runner’s toe). It causes throbbing pain and black/purple nail discoloration. Dr. Biernacki provides trephination (drainage), rules out nail bed laceration requiring repair, and monitors for nail regrowth complications.
What Is a Subungual Hematoma?
A subungual hematoma is a traumatic collection of blood between the toenail plate and the nail bed (germinal and sterile matrix). The confined space creates intense pressure and throbbing pain that can be disproportionate to the apparent external injury. The nail discolors to dark red, purple, or black depending on the amount of blood and time since injury. Large hematomas can ultimately cause the nail to separate from the nail bed and fall off.
Acute trauma — stubbing the toe, dropping a heavy object on the nail, or sports-related impact — is the most common cause. However, runners frequently develop subungual hematomas from repetitive microtrauma: the toenail pressing against the front of the shoe during downhill running or long-distance training. This presentation — “runner’s toe” or “jogger’s nail” — typically affects the hallux (great toe) or second digit and may involve multiple nails simultaneously.
When to See a Podiatrist Immediately
Not every black toenail requires urgent care — but certain presentations demand prompt evaluation. See Dr. Biernacki promptly if: the hematoma involves more than 25–50% of the visible nail surface (higher risk of nail bed laceration); there is associated instability suggesting distal phalangeal fracture; the nail is avulsed (torn away); there is open skin injury beneath or around the nail plate; or a child sustains a crushing nail injury (germinal matrix damage can cause permanent nail deformity if nail bed laceration is unrepaired).
Trephination — Drainage Procedure
Trephination is the procedure of creating a small hole through the nail plate to allow blood to drain and pressure to be released. When performed within 24–48 hours of injury, trephination provides immediate and dramatic pain relief. Dr. Biernacki uses either a heated electrocautery device or a fine-gauge needle to create the drainage hole precisely over the hematoma — the procedure is quick, produces minimal discomfort, and reliably decompresses the blood collection.
After drainage, the hematoma site is cleaned, dressed, and protected. Most patients experience near-immediate relief of the throbbing pressure pain. The nail plate itself may remain intact or may subsequently loosen and detach as the nail bed heals and a new nail grows beneath.
Nail Bed Laceration Assessment
A key diagnostic question for large subungual hematomas is whether a concurrent nail bed laceration is present. Nail bed lacerations — tears in the germinal or sterile matrix — that go unrepaired can cause permanent nail deformity: split nails, ridged growth, or nail absence. Dr. Biernacki’s assessment protocol for significant hematomas includes evaluation for nail plate stability, X-ray to exclude underlying phalangeal fracture (which would classify the injury as an open fracture requiring antibiotic coverage), and examination under nail plate elevation if nail bed laceration repair is indicated.
Repair of nail bed lacerations requires careful microsurgical technique under local anesthesia — fine absorbable sutures restore the matrix topography needed for normal nail regrowth. Post-repair management includes protecting the nail bed during healing and monitoring regrowth for complications.
Runner’s Toe Prevention
Athletes prone to runner’s toe benefit from addressing the mechanical cause rather than repeatedly treating the result. Key prevention strategies include proper shoe fit — shoes should have half a thumb’s width of space beyond the longest toe, with adequate width to prevent digital compression. Running-specific toe socks reduce friction. Keeping toenails trimmed straight and short reduces the nail’s ability to press against shoe material. Moisture-wicking footwear prevents nail softening from sweat.
For athletes with recurring runner’s toe despite footwear optimization, Dr. Biernacki evaluates underlying digital anatomy — unusually long second toes, digital deformities, and hammer toe positions that increase nail-to-shoe contact. Orthotic intervention or corrective toe procedures may be appropriate in persistent cases.
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✅ Pros / Benefits
- Trephination provides immediate pain relief within minutes
- Most subungual hematomas resolve without permanent nail deformity
- Runner’s toe highly preventable with proper footwear assessment
❌ Cons / Risks
- Large hematomas with nail bed laceration require more complex repair
- Nail loss and regrowth takes 9–12 months for hallux nail
- Recurrent runner’s toe may indicate underlying toe deformity requiring correction
Dr. Tom Biernacki’s Recommendation
Black toenails are extremely common — and most don’t need much beyond drainage and reassurance. The ones I take seriously are the large ones in children (nail bed laceration risk affecting permanent growth) and the persistent runner’s cases where I want to understand WHY it keeps happening and fix the root cause, not just drain it again.
— Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle
Frequently Asked Questions
Should I drain my black toenail at home?
Small, painful hematomas can be drained at home with a sterile needle if you’re comfortable — but large hematomas (>50% of nail), injuries with nail instability or avulsion, or injuries in children or diabetics should be evaluated by Dr. Biernacki to rule out nail bed laceration and fracture.
Will my toenail fall off after a hematoma?
Large hematomas frequently cause the nail to loosen and fall off as the blood separates the nail from the nail bed. A new nail will grow — but it takes 9–12 months for the hallux nail and 6–8 months for lesser toes.
How can I prevent runner’s toe?
Ensure shoes have adequate length (half thumb’s width beyond longest toe) and width. Keep toenails trimmed short and straight. Use moisture-wicking socks. Consider Injinji toe socks for long runs.
Is a black toenail always a hematoma?
No — black/dark nail discoloration can also represent melanonychia (nail matrix pigmentation), fungal nail infection, or rarely subungual melanoma. Any dark nail stripe present for more than a few weeks without trauma history should be evaluated.
Does nail trephination hurt?
With proper local anesthesia or appropriate technique, trephination produces minimal discomfort and patients consistently report that the relief from pressure pain immediately after is well worth it.
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Dr. Tom Biernacki, DPM is a double board-certified podiatrist and foot & ankle surgeon at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has reached over one million views.
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