1. Major

• distal femur, proximal tibia, proximal humerus
• in all 3, the tumor arises from the ends of the long bones at the site of tendon insertion
• there appears to be a misdirected growth of the physis resulting in the lateral protrusion of portions of the growth plate causing the development of eccentric, cartilage-capped bony prominences
• the lesion is usually located in the metaphyseal area but with growth, moves away from the physis

2. Minor

• distal radius, distal tibia and proximal and distal fibula
• carpal and tarsal bones
• flat bones (scapula, ilium, rib, skull, sternum)

1. Chondrogenic Cells

• usually benign and do not metastasize
• bone arising from cartilage
• in 0.25%, chondrosarcomatous (malignant) changes can occur in either solitary or multiple osteochrondromas

1. Pain

• tumor is usually not tender but may become so if:
  • following direct trauma to the tumor resulting in an injury to the tumor or a fracture through the stalk of the tumor (hip pain and/or knee pain)
  • the tumor impinges on a nerve
  • the tumor is associated with a bursal sac (exostosis bursata) which is irritated by the movement of adjacent muscles and tendons
  • associated with a malignant transformation

1. Skeletal X-Ray/CT/MRI

2. Bone Scan

• increased uptake of technetium
• cannot differentiate between a benign or malignant exostosis