Bone Lesions & Conditions

Simple Bone Cyst (Juvenile)

Benign bone cavity: fracture risk, injections, and surgical management.

Updated: September 2026·Medically reviewed by Dr. Daniele Priano

Quick Answers

Can bone cysts heal on their own?
Yes, especially 'latent' cysts (distant from the growth plate) can resolve spontaneously with skeletal maturity. 'Active' cysts tend to persist and grow. Even a pathological fracture can paradoxically stimulate healing in some cases.
What is injection treatment and how does it work?
Injection involves introducing substances into the cyst to stimulate healing. Steroids (methylprednisolone) or autologous bone marrow harvested from the iliac crest are used. It is a minimally invasive outpatient treatment that can be repeated at intervals of a few months, with the number of sessions guided by radiographic response rather than a fixed protocol. In Dr Priano's practice, percutaneous treatment is often the first approach in indicated cases.
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Simple bone cyst (also called unicameral or juvenile cyst) is a benign lesion characterized by a single cavity filled with serous fluid within the bone.

It is one of the most common benign bone lesions in children, with peak incidence between 5 and 15 years and male predominance (2:1 ratio).

Most common locations:

  • Proximal humerus (near the shoulder): approximately 50% of cases
  • Proximal femur (near the hip): approximately 25% of cases
  • Less commonly: tibia, calcaneus, radius

Pathogenesis: The exact cause is not yet completely understood. The most accepted theory is a local blockage of venous drainage with accumulation of interstitial fluid that progressively erodes the bone. The cyst grows slowly, thinning the bone cortex.

Classification:

  • Active cyst: located near or in contact with the growth plate (physis). Tends to grow and has higher recurrence risk after treatment.
  • Latent (inactive) cyst: separated from the physis by normal bone. Tendency toward spontaneous resolution with skeletal maturity.

The "fallen fragment sign": Pathognomonic radiographic sign visible when the cyst fractures: a fragment of cortical bone "falls" to the bottom of the cystic cavity, confirming the liquid nature of the contents.

Main risk: Pathological fracture, which can occur even from minor trauma or during normal sports activities. Paradoxically, the fracture sometimes stimulates spontaneous cyst healing.

Assessment and treatment

When to seek evaluation

  • Radiographic finding of lytic area in bone (often incidental)
  • Spontaneous fracture or after minimal trauma (pathological fracture)
  • Persistent localized bone pain
  • Large or extensive cyst, assessed individually
  • Active cyst near the growth plate
  • Marked cortical thinning

What is evaluated

  • Radiographic characteristics: central lytic lesion, sharp margins, cortical thinning
  • Size and relationship to bone diameter
  • Proximity to growth plate (active vs latent)
  • Risk of pathological fracture (cyst index)
  • MRI for atypical lesions or to exclude other diagnoses
  • Functional assessment of the affected limb

Treatment options

  • Clinical and radiographic observation for small, asymptomatic lesions with low structural risk
  • Treatment of a pathological fracture according to its location, stability and alignment, with reassessment of the cyst after union
  • Percutaneous decompression or needling with selected materials or injections, according to the centre's experience and the lesion's characteristics
  • Curettage and bone filling for selected, persistent, recurrent or high-risk lesions
  • Internal fixation when the location and bone fragility require mechanical protection
  • Decisions guided by location, relationship to the growth plate, size, remaining cortex, symptoms, previous fracture and findings at follow-up

Frequently Asked Questions

Can bone cysts heal on their own?▼
Yes, especially 'latent' cysts (distant from the growth plate) can resolve spontaneously with skeletal maturity. 'Active' cysts tend to persist and grow. Even a pathological fracture can paradoxically stimulate healing in some cases.
What is injection treatment and how does it work?▼
Injection involves introducing substances into the cyst to stimulate healing. Steroids (methylprednisolone) or autologous bone marrow harvested from the iliac crest are used. It is a minimally invasive outpatient treatment that can be repeated at intervals of a few months, with the number of sessions guided by radiographic response rather than a fixed protocol. In Dr Priano's practice, percutaneous treatment is often the first approach in indicated cases.
Can my child play sports with a bone cyst?▼
It depends on location, size, and relationship to bone diameter. For cysts judged at higher fracture risk — in weight-bearing bones like the femur, or with very thin cortex — restriction from contact and high-impact sports is advised until healing or post-treatment consolidation.
What happens if the cyst causes a fracture?▼
A pathological fracture through a bone cyst can heal well, but care depends greatly on its location: a lesion in the humerus and one in the proximal femur do not carry the same mechanical risk. After the fracture heals, the cyst is reassessed because it may become smaller, remain unchanged or require specific treatment.
How is a cyst distinguished from a malignant tumor?▼
Simple bone cysts have typical radiographic features: central lytic lesion, sharp margins, no aggressive periosteal reaction. If there is doubt, MRI or biopsy can confirm the diagnosis. Specialist evaluation is important to exclude other lesions.
How many injections are needed?▼
There is no predetermined number. Repeating a percutaneous treatment depends on the technique, radiographic response, location, fracture risk and cyst activity. If healing is not progressing or mechanical risk remains, the strategy is reassessed rather than automatically following a fixed series of injections.

Important Notice: The information on this page is for educational and informational purposes only and does not constitute medical advice. Each clinical case is unique: the appropriate treatment is determined during the specialist consultation, based on a thorough clinical examination and, where necessary, diagnostic imaging. For any doubts or concerns, please consult a specialist.