This study is aimed to provide a clinical and radiographic evaluation of 68 condylar-constrained Total Knee Arthroplasty (TKA) using a single type of prosthesis (Multigen Plus CCK configuration), alone or involving the AMF TT cones, in patients with joint instability or inadequate ligament function, both in complex primary and revision procedures.

This is a post-market, multicentric, prospective, open label study. It is a post-marketing clinical study because the investigational devices are registered, CE marked, and used according to the intended use.

The assignment of any subject involved in the study is determined preoperatively by the aetiology evaluated by the Investigator and falls within the current practice. The decision to use this specific prosthesis design is decided by the Investigators independently and clearly separated from the decision to include the subject in the study.

Baseline measurements (pre-operative clinical assessment and radiographic analysis at discharge) serves as internal control for the assessment of post-operative data.

The study will be carried out in 3 sites in Europe for a total number of 68 study subjects, in whom the decision to implant the Multigen Plus CCK system, alone or in combination with the AMF TT cones, has been taken prior to, and independently from, the decision to include the subject in the study.

The enrolment is competitive until the required recruitment target is met.

The expected number of visits for each study subject is 6, and includes:

• a pre-operative visit (before the subject receives the Multigen Plus CCK system alone or involving the AMF TT cones).
• the intra-operative visit (that is the same day of the surgery).
• the discharge visit (after the surgery according to the clinical practice).
• the following follow-up visits: at 3 months, 12 months, and 24 months after the surgery.

All eligible subjects who agree to participate in the study will be recruited and monitored throughout the duration of the study. For each visit and for each single study subject, radiographic and clinical data will be assessed up to the 24-month follow-up visit according to the standard of care of the site, when applicable. Also, Adverse Events and Serious Adverse Events will be collected and assessed.

Inclusion Criteria:

• Male or female.
• Age ≥ 18 years old.
• Given written informed consent approved by the reference Ethics Committee (EC).
• Subjects in whom a decision has already been made to perform a Total Knee Arthroplasty with Multigen Plus system as per Indication For Use. The decision to implant a Multigen Plus CCK system, alone or involving the AMF TT cones, must be taken prior to, and independently from, the decision to enrol the subject. This decision should be made in accordance with routine clinical practice at the study site concerned.
• Subjects able to comply with the Study Protocol.

Exclusion Criteria:

• Age < 18 years old.
• Subjects with any Multigen Plus system contraindication for use, or any AMF TT cones contraindication for use when used in combination with the Multigen Plus CCK, as reported in the current Instruction For Use.
• Any clinically significant pathology based on the medical history that the Investigator feels may affect the study evaluation.
• Female subjects who are pregnant, nursing, or planning a pregnancy.
• Previous knee replacement on the contralateral side within the last year and whose outcome is achieving an KSS < 70 points.

The subject population for this study includes adult subjects in whom the decision to perform a Total Knee Arthroplasty with Multigen Plus CCK system, alone or involving the AMF TT cones, must be taken prior to, and independently from, the decision to include the subject into the study.