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Knee Joint Replacement (cont.)

Exams and Tests

Your doctor will base your diagnosis on clinical examination and X-rays.

  • A fracture usually involves a bone directly above or below your new knee. Most commonly your thighbone (femur) breaks just above its connection with the knee replacement.
  • As the new joint begins to wear, your knee may not glide smoothly through its range of motion. You likely will notice that movements are painful now that were not painful in the past. An X-ray can help to determine if there is loosening or abnormal wear of prosthetic components.
  • Pain from infection does not go away with rest, and fluid may begin to build up in the knee joint.
    • The doctor can sample any fluid through arthrocentesis, a procedure of drawing the fluid out of the affected joint with a needle and syringe. The removal of fluid will decrease the pain but more importantly the fluid will be sent to the laboratory for examination and to help make a decision if an infection is present and how to treat it.
    • Blood tests also may be performed.
  • An X-ray can confirm a knee dislocation. A doctor must assess any damage to nerves, blood vessels, or muscles besides the dislocation itself.
  • A blood clot often causes pain and swelling in your leg farther from your heart than where the clot sits. That area may become red and feel warm.
    • Your doctor may perform a Doppler ultrasound test, especially for a clot suspected to be above your knee. This evaluates the flow of blood in that area.
    • The doctor may also order a venogram of your leg. In this test, dye is injected into a vein, and X-rays are assessed to look for evidence of a blood clot in a deep vein of the leg. Without the dye, the veins would not show up on an X-ray.
Medically Reviewed by a Doctor on 3/23/2015

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