This study compares and evaluates differences in movement analysis, patient-reported outcome between patients undergoing total knee arthroplasty with use of either Zimmer Biomet NexGen with posterior stabilization and Bioimplanti K-Mod cruciate-retaining with dynamic congruence

The aim of this study is to assess and compare kinematic and time-space gait parameters in patients after total knee arthroplasty, who will undergo the surgery with the use of either posterior-stabilized (PS) or dynamic congruence (DC) implants.

Materials and methods To this study 56 consecutive patients undergoing total knee arthroplasty will be recruited. Study protocol is designed as a prospective, blinded, parallel-group, superiority trial, with balanced randomization [1:1]. All participants will be operated in single clinical orthopedic department, by single high-volume surgeon, who performed more than 3000 total knee arthroplasties in his professional career.

Before the surgery patients will fulfill the author's questionnaire concerning their age, height and body mass, level of activity and VAS (Visual Analogue Scale).

After the surgery 1 to 3 years postoperatively three-dimensional gait analysis will performed with use of BTS SMART device. This device uses passive markers technology and registers the movement by six cameras. To perform full gait analysis several data concerning patients anthropometry will be collected (lower limb length, knee and ankle joint width, width and depth of the pelvis). Whole gait analysis will be performed by experienced single clinical biomechanist accordingly to the Davis protocol. Markers will be installed on the patients' limbs on the following points: base of sacral bone, greater trochanter of the femur, lateral femoral condyle, head of the fibula, lateral malleoli, head of the V metatarsal bone).

Participants will walk barefoot for 10 meters quadruple times. Following time-space and kinematic parameters will be assessed:

Time-space parameters Single stance time (T1) [%] Swing time (T2) [%] Double-stance time (T3) [%] Step length (SL) [m] Mean gait velocity (Vm) [m/s] Cadence (C) [number of steps/min]

Kinematic parameters:

Operated knee range of flexion during swing phase [°]

Inclusion Criteria:

• agreement to participate in the study
• BMI (kg/m2) less than 40
• ability to walk for 10 meters
• knee flexion more or equal of 90 degrees

Exclusion Criteria:

• unwillingness to participate in the study
• osteoarthritis due to the rheumatological disease
• disorders associated with nerve-muscle signal transmission
• neurological disorders associated with dizziness, nystagmus or other conditions that might influence balance during activity

Participant will not be informed which type of prosthesis was used in their particular case.

Outcomes Assessor will not be informed which type of prosthesis was used in particular patient.