The goal of this observational study is to compare the functional outcome of patients with end-stage knee osteoarthritis (OA) before and after total knee arthroplasty based on the phase angle level.

The main questions it aims to answer are:

• Do patients with low phase angle show worse functional recovery after total knee arthroplasty compared to those with high phase angle?
• Is postoperative physical function associated with preoperative phase angle level?

Researchers will compare postoperative physical function and muscle strength between the low and high phase angle groups to determine whether a low phase angle is associated with poorer functional recovery.

Participants will:

Perform physical function tests, isokinetic strength assessments, and bioelectrical impedance analysis before and three months after surgery.

After obtaining informed consent, a pre-surgical screening is conducted. Participants complete a history survey, a sarcopenia questionnaire, and the International Physical Activity Questionnaire (IPAQ).

The screening includes a comprehensive evaluation of baseline symptoms, followed by functional assessments that incorporate bioelectrical impedance analysis, muscle strength testing, and performance-based tests:

• A modified Charlson Comorbidity Index (CCI) is used to assess comorbidity burden, and a Numeric Pain Rating Scale (NPRS) records participants' initial pain levels.
• Radiographic assessments are performed to evaluate the frontal alignment of the lower extremities and the radiographic severity of knee osteoarthritis (OA) using the Kellgren-Lawrence (K-L) grading system.
• Multifrequency bioelectrical impedance analysis (BIA) is used to measure phase angle and body composition.
• Handgrip strength is measured through three trials on each side, with the average recorded.
• Knee strength is measured using an isokinetic dynamometer.
• Performance-based tests include the 10-meter walk test, the Timed Up and Go (TUG) test, and the Berg Balance Scale (BBS).

Follow-up assessments are conducted three months after total knee arthroplasty, with participants undergoing the same protocol for performance-based tests, isokinetic knee strength evaluation, and bioelectrical impedance analysis.

Inclusion Criteria:

• Individuals aged 55 and over (based on the age on their national ID at the time of consent)
• Individuals diagnosed with knee OA based on medical history, physical examination, and radiographic assessments.
• Individuals who plan to perform total knee arthroplasty

Exclusion Criteria:

• Individuals with gait disturbance due to neurologic disorders such as Parkinson disease, stroke and dementia
• Individuals with severe cardiac, pulmonary, or musculoskeletal disorders that limited quadriceps strength and physical function
• Individuals with knee osteoarthritis due to secondary causes such as rheumatic or traumatic arthritis
• Individuals with a history of any knee surgery within one year.
• Individuals considered clinically unsuitable for the study by the researchers or person in charge based on significant medical findings.

Single general hospital