Knee replacement surgeries are performed to help people with end-stage arthritis in their knees get rid of pain and return to an active lifestyle. Knee replacements can fail, and can fail from a myriad of reasons. The first cause of knee replacement failure to be discussed is instability.
Knee replacement instability results in an unstable knee that is painful. The typical patient develops pain around the ligamentous attachments of the knee including the medial knee, lateral knee, and anterior knee. The typical patient has pain with getting up from sitting when the knee is flexed. Other complaints can include the knee giving out, knee swelling, difficulty with stair climbing, and pain that never got better from the time of surgery.
Many times, patients would have sought multiple opinions and would have been advised that the knee replacement "looks good," or that they have reached full recovery and might have to "deal" with the pain they have. That is not uncommon because the diagnosis can be a subtle one to make; the typical unstable knee doesn’t appear infected, and x-rays don’t typically show any signs of failure. The clinching finding is the examination as unstable knees would be lax to stress examination.
The treatment for an unstable knee is usually begun with physical therapy or knee bracing. A number of unstable knee replacements would not respond to non-surgical measures. Surgical management (revision) usually begins with ruling out an infection as an infection could be present even in the case of knee instability.
Knee revisions/re-dos for instability require careful planning, and depending on the pattern of instability on physical examination, could range from just a polyethylene exchange ("plastic" exchange) to changing one or both metal parts (femoral component, or femoral and tibial components).
The goal of knee revision surgery for instability is to restore ligamentous balance to the knee. This usually results in improvement in functioning and symptoms; unfortunately, the results don’t always rival the results from a primary knee replacement.
Dr. Oluwaseun Akinbo M.D. is an orthopedic surgeon at HaysMed. For more information, check www.haysmed.com/oluwaseun-akinbo