The goal of the clinical trial is to evaluate the efficacy of the AtMoves Knee System in the clinical diagnostic process of aseptic loosening in patients with a knee prosthesis. The main question it aims to answer is:

Does the use of the AtMoves Knee System reduce the percentage of failed outcomes? A "failed outcome" is defined as a change in the patient-reported Knee injury and Osteoarthritis Outcome Score (KOOS-PS) that is lower than the minimal clinically important difference at 12 months.

Researchers will compare two groups: The first group will undergo an additional CT scan using the AtMoves Knee System. The second group will not undergo these scans. Both groups are allowed to undergo additional diagnostic measures. Researchers will compare the percentage of "failed outcomes" between these groups.

During the one-year follow-up, participants in both groups will be asked to fill out questionnaires.

Inclusion Criteria:

• Age 18 years or older.
• Subjects must have underwent either unilateral or bilateral TKA surgery.
• Aseptic loosening is one of the differential diagnoses of the treating orthopaedic surgeon
• The treating Orthopaedic Surgeon is uncertain of the diagnosis after anamnesis, physical examination and conventional x-ray.
• The surgeon wants additional examinations or additional imaging to arrive at the diagnosis and proposal for treatment.
• Subjects must be capable of giving informed consent and must be willing to undergo examination with the AtMoves Knee System.

Exclusion Criteria:

• A clear other cause for complaints other than aseptic loosening (e.g. septic loosening, neuropathic pain, non-consolidated peri-prosthetic fracture of the bone around the TKA)
• Surgical interventions of the index knee in the year prior to the start of the complaints associated with TKA loosening.
• Posttraumatic or congenital deformation of the leg for which the loading device does not fit.
• Pregnancy or suspected pregnancy.
• Unable or unwilling to understand or sign the informed consent for this study and to undergo examination with the AtMoves Knee System.

IPD will not be made pubicly available but can be obtained upon request at the study's sponsor. When a valid reason for the re-use of study data is provided, a Data Sharing Agreement can be set up.