A total of 34 patients aged between 50-80 years, diagnosed with first carpometacarpal joint osteoarthritis based on hand radiographs taken within the last 3 months, will be included in the study from the Physical Therapy and Rehabilitation outpatient clinic. Sociodemographic data such as age, gender, height, weight, and BMI will be recorded. Based on their current radiographs, patients will be classified into two groups according to the Eaton-Littler classification: Stage 1-2 (early stage) and Stage 3-4 (advanced stage). Pain levels will be assessed using the Visual Analog Scale (VAS). Hand grip strength will be evaluated with a Jamar hand dynamometer, and pinch grip strength will be assessed with a Jamar pinch meter. The thicknesses of the abductor pollicis brevis, first dorsal interosseous, and opponens pollicis muscles will be measured using ultrasound. All assessments will be performed separately for the dominant and non-dominant hands.

Inclusion Criteria:

• Patients aged 50-80 years.
• Diagnosed with first carpometacarpal joint osteoarthritis.
• Presence of a hand radiograph taken within the last 3 months.
• Volunteered to participate in the study.

Exclusion Criteria:

• Refusal to participate in the study.
• Use of medications that may suppress osteoarthritis flares.
• Presence of rheumatologic diseases causing peripheral joint involvement.
• History of fractures or surgeries involving the first carpometacarpal joint.
• Presence of psychiatric disorders.
• Presence of cognitive impairments that could hinder understanding or performance of study-related tasks.

The study population includes patients aged 50-80 years with first carpometacarpal joint osteoarthritis, classified into early and advanced stages based on radiographs, excluding those with confounding medical or cognitive conditions.