Quadriceps Muscle Quality and Clinical Outcomes in Knee Osteoarthritis

The purpose of this cross-sectional, observational study is to evaluate the relationship between quadriceps muscle quality-specifically muscle echogenicity and thickness change during isometric contraction-and clinical outcomes such as pain, physical function, quality of life, and Patient Global Assessment (PtGA) in female patients with knee osteoarthritis. Participants will undergo a non-invasive ultrasound evaluation of their thigh muscles and complete standard clinical questionnaires to help determine how muscle structural and functional properties impact the daily lives of patients with knee osteoarthritis.

Inclusion Criteria: * Female sex * Aged between 40 and 70 years * Diagnosed with clinical and radiographic primary knee osteoarthritis (Kellgren-Lawrence Grade 2 or 3) * Ability to perform isometric contraction at 90° of knee flexion * Voluntary participation and provision of written informed consent Exclusion Criteria: * History of knee surgery within the last 6 months * Intra-articular injection (e.g., corticosteroids, hyaluronic acid) within the last 3 months * Presence of inflammatory rheumatic diseases (e.g., Rheumatoid Arthritis, Spondyloarthropathy) * Known neuromuscular disorders affecting the lower extremities * Severe cardiopulmonary comorbidities that prevent participation in clinical assessments * Severe patellofemoral instability