What are the causes of a hematoma on the shin?

Causes of Hematoma on the Shin

Shin hematomas result primarily from direct blunt trauma to the tibia, where the bone's superficial location makes it particularly vulnerable to injury, with bleeding occurring from disrupted blood vessels in the periosteum, subcutaneous tissue, or muscle compartments.

Primary Traumatic Causes

Direct Blunt Trauma

• Direct impact to the shin is the most common cause, as the tibia lies immediately beneath the skin with minimal soft tissue protection, making it highly susceptible to contusion injuries 1
• Falls, sports injuries, motor vehicle accidents, and direct strikes to the lower leg account for the majority of shin hematomas 2
• The mechanism involves rupture of small blood vessels in the subcutaneous tissue, periosteum, or adjacent muscle compartments following impact 1

Fracture-Associated Bleeding

• Tibial fractures can cause significant hematoma formation due to injury to the nutrient artery of the bone or disruption of periosteal blood vessels 3
• High-energy injuries produce greater tissue damage and larger hematomas compared to low-energy mechanisms 4
• Subperiosteal hematomas specifically arise from disinsertion or rupture of muscle tendons or injury to nutrient arteries after blunt trauma to bone 3

Secondary and Predisposing Factors

Coagulopathy and Anticoagulation

• Anticoagulant therapy significantly increases the risk and severity of hematoma formation following even minor trauma 5
• Bleeding disorders (inherited or acquired) can dramatically amplify hemorrhage from traumatic injuries 2
• Anticoagulant therapy alone likely does not trigger spontaneous bleeding but requires an additional precipitating factor such as trauma or a vascular weakness 5

Vascular Abnormalities

• Vascular malformations represent the third most common category of causes for spontaneous hematomas when no clear trauma is identified 5
• Traumatic pseudoaneurysm from branches of arteries (such as the superior gluteal artery in pelvic trauma) can cause expanding hematomas, though this is rare in the shin 3

Spontaneous or Idiopathic Causes

• In up to 29.7% of cases, no clear etiological factor can be identified as the cause of hematoma formation 5
• Chronic expanding hematomas can present as slowly growing masses without recent trauma history, though these are uncommon 6

Clinical Implications and Complications

Tissue Pressure and Necrosis

• Accumulation of blood in tissues can result in necrosis of overlying skin due to increased tissue pressure 1
• Multiple cellular and biochemical changes leading to tissue ischemia and necrosis can occur even without significantly elevated tissue pressure 1

Timing and Evolution

• Most soft-tissue hematomas acutely appear and spontaneously resolve 6
• Some hematomas present as swellings that slowly expand and progressively increase over time, requiring differentiation from soft-tissue neoplasms 6
• Prompt recognition and evacuation should be performed when significant tissue pressure develops or skin viability is threatened 1

Key Clinical Pitfalls

• Do not assume all shin swelling is simple bruising—assess for compartment syndrome signs, particularly in high-energy trauma 4
• Consider underlying coagulopathy or anticoagulation in patients with disproportionately large hematomas relative to the reported trauma mechanism 5
• Chronic expanding hematomas can mimic soft-tissue sarcomas on imaging, potentially requiring biopsy for definitive diagnosis 6
• The incidence of lower extremity hematomas is approximately 33 per 10,000 individuals annually, making this a relatively common clinical problem 1