Carpometacarpal (CMC) joint osteoarthritis is a disorder that is estimated to affect more than one-third of postmenopausal women, leading to decreased muscle strength, reduced joint range of motion, and pain.The pathogenesis of thumb CMC osteoarthritis involves complex interactions between biomechanical forces, genetic predisposition, hormonal changes, repetitive microtrauma, and aging. An important factor in the progression of carpometacarpal osteoarthritis is the loss of joint stability provided by the surrounding muscles (2). The common methods for diagnosing thumb CMC OA is plain radiographs and clinical examinations. However, radiographs are unable to assess the role of surrounding structures, including muscles and ligaments.

Ultrasound is a cost-effective, radiation-free, and easily applicable imaging method.

In this cross-sectional study, patients with various stages of 1st carpometacarpal (CMC) joint osteoarthritis (OA) were assessed using standard radiographs based on the Modified Eaton Litter classification. Postmenopausal women with clinical and/or radiological evidence of 1st CMC OA will be included (Group 1). In the healthy control group, subjects will be matched based on age and hand dominance (Group 2). Demographic information including age, sex, height, weight, body mass index (BMI, kg/m²), dominant hand, and symptom duration (in months) will recorded. Pain levels will be assessed using the Visual Analogue Scale (VAS).The thickness of the thenar eminence muscles (longitudinal thickness of the first dorsal interosseous muscle (FDI), abductor pollicis brevis (APB), and opponens pollicis (OPP)) was measured using musculoskeletal ultrasound. Muscle strength in both hands will be evaluated using grip strength measured with a dynamometer . Pressure pain threshold (PPT) for painful and non-painful finger joints will be assessed using a hand-held algometer

Inclusion Criteria:

Postmenopausal women with clinical and/or radiological evidence of 1st CMC OA

Exclusion Criteria:

• De Quervain's tenosynovitis, flexor carpi radialis tendon pathology, and carpal tunnel syndrome, as well as those with hand trauma or hand surgery within the past year, had received steroid and local anesthetic injections into the 1st CMC joint within the last 3 months, or had connective tissue disorders, rheumatologic, or autoimmune diseases

Postmenopausal women with clinical and/or radiological evidence of 1st CMC OA