Instability as a cause of failure of total knee replacement

This is the first in a series of posts discussing causes of failure of total knee replacement.

  Primary total knee replacement surgeries are usually performed to help people with end-stage degenerative changes of their knees get rid of pain and return to a more active lifestyle. Knee replacement surgeries are generally successful and represent one of the most successful procedures in orthopedic surgery and medicine in general. However, knee replacements can fail. Knee replacements can fail from a myriad of reasons. The first cause of total knee replacement failure to be discussed in this series is instability. 

          Total knee replacement instability results in an unstable knee. An unstable knee could be very painful. The typical patient, over time, develops pain around the ligamentous attachments of the knee including the medial knee (medial collateral ligament insertion points), lateral knee (lateral collateral ligament insertions points), and anterior knee (quadriceps and patellar tendon insertion points). The typical patient would complain about pain or difficulty with getting up from sitting when the knee is flexed. Other complaints can include the knee giving out, recurrent effusions, difficulty with stair climbing, and pain that never got better from the time of knee replacement surgery. 

          Many times, affected people would have sought multiple “second” opinions and could have been advised that the knee replacement “looks good”, or that the patient has reached full recovery and they might have to deal with the residual pain they have. Such occurrences would not be uncommon because diagnosis can be a subtle one to make; the typical unstable knee replacement doesn’t appear infected on examination, and x-rays don’t typically show any signs of gross failure unless a traumatic injury precipitated the instability symptoms. 

          A fellowship trained joint surgeon should be able to diagnose an unstable knee replacement. The above complaints and scenarios are very suspicious for an unstable knee replacement. The clinching finding is the examination as unstable knees would be lax to varus or valgus knee stress on physical examination. An unstable knee can be lax in full flexion, mid flexion, extension, and also globally (i.e in full flexion, mid flexion, and in extension). Sometimes, an x-ray with less than ideal component positioning could also tip a surgeon to suspect an unstable knee; however, most unstable knees are not a function of components not ideally positioned but more a result of unbalanced knee ligaments. 

         The treatment for an unstable knee is usually begun conservatively with physical therapy or knee bracing. However, a good number of unstable knees would not respond to these non -surgical measures. Surgical management 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 insert exchange (“plastic exchange”) to a one component exchange (usually femoral component and obligate polyethylene insert exchange) to two component exchange (femoral and tibial components, and obligate polyethylene insert exchange). Knee revision surgery is more complex than a primary knee replacement surgery, and can be expected to take longer, involve more blood loss, require revision components, and involve more extensile surgical exposure. This can impact the rehabilitation process, and it might be slower when compared to rehabilitation from a primary knee replacement. 

          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, but the results don’t always rival the results from a primary knee replacement.

          If you have a painful knee replacement and haven’t been able to figure out the cause, call Hays Orthopedic Institute at 785 261 7599 to schedule an appointment with Dr. Akinbo.