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It is the most common benign bone tumor(not a true tumor). It consists of a bony base or stalk with a cartilage capQ that projects from the normal bone away from a nearby joint.

It is most common benign bone tumor. (NOT A TRUE TUMOR)


it is a developemental disorder caused by misdirected growth of a portion of physeal plate that is projected laterally.


Most common site is knee.

It can be solitory or multiple


when present in multiple numbers it is part of condition called Multiple Hereditory Exostosis:MHE , also called diaphyseal aclasia.

Treatment in most cases is observation. Surgery(excision) is reserved for either cosmetic or complication like bursitis, mechanical (restriction of joint movement),malignant transformation


Malignant transformation is seen in 1 %(solitory) or 5% in MHE.


More incidence of Malignant transformation is seen in proximal lesions,sessile lesions.


Indicator of malignant transformation is increased cartilage cap (more than 2 cm)


Radiographic Findings

  1. Lesion protrudes from the host bone on either a (broad based) or peduncuar bony stalk. 2 - 12cm in size.
  2. It looks smaller than it feels because the cartilage cap is not seen on x –ray.
  3. There may be slight metaphyseal widening at the site of exostosis.

A.     B. Description: images-1

A. Osteochondroma pedunculated B. Osteochondroma sessile


  1. Excision of OC should, if possible, be postponed until later adolescence due to risk of recurrent and growth arrest.
  2. Excision should be reserved for lesion that causes pain, symptomatic impingement on neurovascular structure, compromise of joint function, spinal cord compression, obvious cosmetic deformity, growth disturbance (angular deformity or limb length discrepancy), false aneurysm formation, painful bursa formation and rapid increase in size of lesion.


  1. It is a rare hamartomatous bone tumor occurring most commonly in spine > skull and pelvis. It consists of vascular channels capillary, venous or cavernous. These tumors are benign in character.
  2. They are usually symptomless and are incidentally discovered
  3. In spine characteristic appearance is presence of vertical parallel lines or coarse vertical trabeculations (Corduroy appearance) of vertebral body, and increased density. In flat bones appearance suggests malignancy, but there is no associated cortical or medullary destruction.
  4. In extremities local gigantism may occur

  Description: images-3

Polka dot axial view on CT scan

Codrouy pattern

Synovial Chondromatosis

  1. Proliferative disorder of synovium
  2. Associated with cartilage metaplasia
  3. Multiple intraarticular loose bodies in joint.

Pigmented Villonodular Synovitis

  1. Monoarticular reactive synovial disease characterized by proliferation of synovial villi
  2. Knee most common site followed by hip
  3. Extra articular lesion is is called giant cell tumor of tendon sheath in foot and hand.
  4. Responsible for atraumatic recurrent hemarthrosis.
  5. Contains hemosiderin stain multinucleoted giant cell.

Clinical features:

  1. Almost always monoarticular.
  2. Presents between 20 – 40 years of age.
  3. Knee is the most common site.
  4. Second most common site is hip
  5. Proliferated synovial membrane gets caught between articular ends of bone and create locking.
  6. Joint aspiration reveals brown coloured or serosanguinous fluid.


  • Treatment of choice synovectomy
  • Radiotherapy for recurrent cases


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