Total knee arthroplasty (TKA) is currently the international standard for the treatment of degenerative and rheumatological diseases of the knee joint, as well as certain types of fractures. Although TKA is a procedure that has been shown to be effective in relieving pain and improving function in patients with osteoarthritis, approximately 20% of patients are dissatisfied with the results. Traditional methods of assessing the outcome after joint arthroplasty often focus on objective indicators of surgery and neglect the needs and opinions of patients. Because of this, this research project has the aim to know the effectiveness of two models of stabilization of total knee prostheses on the functionality achieved and perceived by the patient, as well as in the knee joint biomechanics during movement in activities of daily life. On the other hand, as a secondary objective, we propose to determine prognostic biomarkers of knee prosthesis function based on radiological information, quantification of cytokines, intra-articular markers, and biomechanical functional evaluation that correlate and predict a correct evolution of patients with a knee replacement.

To carry out these objectives, 80 participants will be included with an indication to perform total knee joint replacement surgery. Participants will be randomized allocated into two groups: i. participants with a prosthesis with medial condylar stabilization ii. participants with a traditional prosthesis with central pivot stabilization. Participants will be evaluated at five-times: before surgery, immediate postsurgical, at 3 months of evolution, 6 months of evolution, and one year of evolution.

I. Objectives

Due to the information reviewed, this research project has the following aims:

1. To determine the effectiveness of two different prosthesis stabilization procedures of TKA on the functionality achieved and perceived by the patient, as well as on the knee joint biomechanics during movement in activities of daily life.
2. As a secondary objective, we propose to determine prognostic biomarkers of knee prosthesis function based on radiological information, quantification of cytokines, intra-articular markers, and biomechanical functional evaluation that correlate and predict a correct evolution of patients with knee replacements.

II. General procedures

The study has the approval of the Ethical Committee for Research with Drugs of the University Clinical Hospital of Valencia. Likewise, this study will be conducted at the University Clinical Hospital of Valencia with the INCLIVA Health Research Institute and the University of Valencia (Spain). All assessment procedures will be performed at the Evaluation Unit in Personal Autonomy, Dependence, and Mental Disorders of the Faculty of Medicine at the University of Valencia.

III. Methodology

III.1. Study design

The PROKnee trial was designed as a randomized, controlled, and triple-blinded (patient, raters, and data analysts) with two parallel groups.

III.2 Participants

The inclusion criteria are:

• People between 50-85 years old and,
• Primary total knee prosthesis surgery indication with patellar fitting.

The exclusion criteria are as follows:

• Previous lower limb joint prosthesis,
• History of fracture or surgery in the lower limb or lumbar spine,
• Disabling contralateral knee pain,
• Lower limb length asymmetry > 2 cm,
• Walking impairment due to other causes non-related to the knee pathology,
• Body Max Index > 39, and
• Severe surgical complications such as infection, aseptic loosening, deep vein thrombosis, periprosthetic fracture, and arthrofibrosis.

III.3 Assessment and Outcomes

The study participants will be evaluated in five periods of evolution: before surgery, immediately after surgery, at 3 months of evolution, at 6 months of evolution, and a year after having performed the surgery.

The set of tests to be carried out in each evaluation time and the data to be recorded are the following:

Personal and Anthropometric data:

• Age (years), Sex (men/women), Gender, BMI (kg/m2), race, level of education, marital status, height, weight, number of chronic diseases besides osteoarthritis, length of inferior extremities measured weight-bearing from the anterior iliac spine (AIS) to the medial malleolus, % of body fat, % of body water.
• Chronicity of knee symptoms; Diagnosis, Surgical approach, Prosthetic implant, Side of surgery, Days of hospital stay, Leg swelling evaluation with thigh and calf circumference, Hospital readmission, Post-cx complications, Fall Incidence.

Assessment scales:

• To assess knee and other joint pain it will be used the Visual Analog Scale (EVA).
• To assess knee function it will be used the Knee Osteoarthritis Outcome Score (KOOS).
• To assess pain, stiffness, and function it will be used the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).
• To assess physical activity it will be used the University of California, Los Angeles Physical Activity Questionnaire (UCLA).
• To assess health-related quality of life it will be used the EuroQol Group 5-dimensions-Level 5 (EQ5D5L) and the Short Form-12 Physical Functioning (SF-12).
• To assess cognitive state it will be used the Screen for Cognitive Impairment in Psychiatry (SCIP).
• To assess joint awareness it will be used the Forgotten joint score-12 (FJS-12).
• To assess anxiety and depression it will be used the Hospital Anxiety and Depression Scale (HADS).

Radiological and Laboratory tests:

• Imaging tests by radiography on the operated knee
• Carrying out computed tomography in cases of inadequate function, to identify possible causes, without subjecting the patients to excessive irradiation.
• Determination of Serum Levels of inflammatory biomarkers status: Interleukin-6, procalcitonin, calprotectin, and C-reactive protein.
• Determination of intra-joint biomarkers: C-reactive protein, and alpha-defensin.

Biomechanical functional assessment:

• Range of motion in both knees.
• Isometric knee strength flexion and extension of the operated and contralateral knee.
• Lower limb proprioception.
• Balance assessment during standing position.
• Kinematic assessment of the lower limb during 1) Six-minute walking test gait, 2) Timed up-and-go test, 3) Gait, 4) Sit to stand Test, 5) Step-over, 6) Stepping up and down stairs.

III.4 Intervention

Participants will be randomized and allocated into two groups: 1) participants with a prosthesis with medial condylar stabilization and, 2) participants with a traditional prosthesis with central pivot stabilization.

III.5 Sample size, recruitment, and randomization

The sample size was estimated based on previous works that compare the medial stabilization knee prosthesis with another device. A small-medium effect (f = 0.15), a statistical significance of 5% at the two-tailed level, and a power of 90% are set, which gives a total of 82 people to be recruited. If 20% of the possible dropouts are considered, the initial recruitment will be of 99 people. Because patient recruitment will occur over a prolonged period, the assignment to the groups will be performed as block randomization with a 1:1 allocation.

The inclusion criteria are:

• People between 50-85 years old and,
• Primary total knee prosthesis surgery indication with patellar fitting.

The exclusion criteria are as follows:

• Previous lower limb joint prosthesis,
• History of fracture or surgery in the lower limb or lumbar spine,
• Disabling contralateral knee pain,
• Lower limb length asymmetry > 2 cm,
• Walking impairment due to other causes non-related to the knee pathology,
• Body Max Index > 39, and
• Severe surgical complications such as infection, aseptic loosening, deep vein thrombosis, periprosthetic fracture, and arthrofibrosis.

The study participants, researchers who perform the functional assessments, and data analyst are unaware of the type of prosthetic stabilization used. They will not have access to the hospital medical history where the surgical procedure will be specified. The two surgeons in the study know the type of prosthesis used in each patient, and if the patient requests it, the technical specifications of the stabilization used are disclosed.