Active Knee Prosthesis Study

Inclusion Criteria: * Male or Female age 22-65. * The patient must have a unilateral transfemoral amputation . * The patient must have the ability to ambulate at variable cadence (an expected lower extremity prosthesis functional level of K3 or above). * The patient must have adequate socket to support the device. Exclusion Criteria: * Women who are pregnant. * Severe co morbidity, atypical skeletal anatomy, or poor general physical/mental health that, in the opinion of the Investigator, will not allow the subject to be a good study candidate (i.e. other disease processes, mental capacity, substance abuse, shortened life expectancy, vulnerable patient population, BMI \>40, etc.).