Secondary Knee Osteoarthritis due to Neurofibromatosis Type 1 Treated with above the Knee Amputation: A Case Report

Background. Neurofibromatosis Type 1 (NF-1) has a variety of associated orthopaedic manifestations that have been previously reported. We report a case of severe, grade 4 knee osteoarthritis (OA) with recurrent subluxation and joint laxity due to multiple extra-articular neurofibromas ultimately treated with Above the Knee Amputation (AKA). Case Description. A 39-year-old man presented with multiple neurofibromas and lymphedema leading to degenerative changes of the knee. Conservative treatment failed due to the severity of the knee degeneration and patient discomfort. Likewise, arthroplasty was not possible due to poor bone quality and joint instability. Therefore, AKA was selected to relieve symptoms and provide functional improvement. six months after the procedure the patient has increased functional capacity for ambulation and activities of daily living, as well as significant decrease in pain and discomfort. Clinical Relevance. Extra-articular neurofibromas causing severe secondary OA in relatively young patients can be functionally improved with AKA and prosthetic device use.