De Quervain's disease is a painful tenosynovitis of the abductor pollicis longus and extensor pollicis brevis muscle tendons located in the first dorsal compartment. The primary treatment for De Quervain's disease is conservative; surgical intervention is rarely required. Currently, there is no standardized treatment protocol supported by strong, up-to-date evidence.

The aim of this study is to compare the effectiveness of a static hand-wrist resting splint and exercise therapy in the conservative treatment of De Quervain's tenosynovitis. Patients will be evaluated in terms of pain levels, functional/symptom status, hand-finger strength, pressure pain threshold (PPT), tendon cross-sectional area measured by ultrasound, and the presence of effusion findings (semiquantitative; 0-3), and patient satisfaction.

Patients who meet the inclusion and exclusion criteria will undergo a detailed clinical examination and medical history review, after which written informed consent will be obtained. They will then be randomly assigned to one of the two treatment groups using block randomization.

Baseline sociodemographic data (age, sex, body mass index, employment status, education level, marital status) and clinical variables (dominant hand, symptom duration, comorbidities, affected hand, presence of the Finkelstein sign, pain severity, functional/symptom status, hand-finger strength, pressure pain threshold (PPT), and ultrasonographic findings) will be recorded.

Patients in the first group will be provided with a static wrist-hand resting splint with thumb support, extending to the distal forearm. They will be instructed to wear the splint for at least 6-8 hours per day for a minimum of 4 weeks. Additionally, both groups will receive training on activity modification and positioning.

Patients in the second group will be given a home exercise program. They will perform the exercises twice daily for 6 weeks, with each exercise consisting of 10 repetitions. All patients will be evaluated at baseline, at the second week of treatment, and at the end of the sixth week.

Outcome measures will include clinical examination findings (Finkelstein test), pain severity [Visual Analog Scale (VAS) at rest and during activity], the Turkish versions of the Disabilities of the Arm, Shoulder and Hand (DASH) Questionnaire, Health Assessment Questionnaire (HAQ), and Patient-Rated Wrist Evaluation (PRWE), patient satisfaction, handgrip and finger pinch strength measurements, and pain pressure threshold using an algometer.

Ultrasound evaluations of the abductor pollicis longus and extensor pollicis brevis tendons in the first dorsal compartment including the measurement of the cross-sectional area (csa) will be performed at baseline, week 2, and week 6.

All assessments will be conducted by the same blinded investigator who is unaware of the group allocations

Inclusion Criteria:

• Adults aged between 18 and 65 years

Patients experiencing wrist pain and tenderness for less than 3 months and clinically diagnosed with acute or subacute De Quervain's tenosynovitis

Visual Analog Scale (VAS) pain score ≥ 3

Exclusion Criteria:

• History of trauma

Wrist fractures

Local infection

Presence of rheumatologic diseases (e.g., rheumatoid arthritis, psoriatic arthritis)

Presence of symptomatic hand osteoarthritis

Continuous use of nonsteroidal anti-inflammatory drugs (NSAIDs) or corticosteroids

Receipt of physical therapy for the hand or wrist within the past 3 months

Corticosteroid injection into the hand or wrist within the past 3 months

Diagnosed with significant neurological disorders (e.g., upper motor neuron disease)

Presence of uncontrolled systemic diseases (e.g., uncontrolled diabetes mellitus, congestive heart failure, chronic kidney disease, hepatic failure)

Major psychiatric disorders

Communication difficulties