A connection adapter between a rigid transcutaneous implant can be anchored intracorporeally in a femoral stump, and a part of an extracorporeal orthopaedic knee joint. The connection adapter comprises a first coupling part for connection to the transcutaneous implant and a second coupling part for connection to the knee joint. The second coupling can be connected releasably to the first coupling part. A safety coupling is arranged in the interior of the second coupling part and transfers a torsional moment between the first coupling part and the second coupling part and slips through when an adjustable maximum value of the torsional moment is exceeded.