Background: Rhizarthrosis (trapeziometacarpal osteoarthritis) is the second most common site of osteoarthritis in the hand affecting 10-30% of adults over the age of 50. Up to four times as many women as men have rhizarthrosis. Clinical symptoms include functional disability of the thumb, pain, joint swelling, and reduced strength. The first carpometacarpal joint is pivotal in the opposition of the thumb and allows a high degree in flexibility to humans. Current therapies focus mainly on surgical strategies, which should be considered in advanced, therapy-resistant stages to relieve pain and improve function. However, conservative treatment methods are urgently required in presurgical stages. The efficacy of conservative treatment options for rhizarthrosis, which are intended to preserve function, joint integrity and to relieve pain, has not been adequately studied. In the clinical study protocol presented here, we investigate the efficacy of multimodal hand therapy versus therapeutic ultrasound versus combination therapy with both hand therapy and therapeutic ultrasound. Methods: This study is a single-center, randomized, controlled, parallel-group pilot trial. One hundred fifty patients with rhizarthrosis and current disease activity will be randomized to one of three conservative interventions over 6 months. Interventions are (1) multimodal hand therapy (2) therapeutic ultrasound, and (3) combination therapy with both hand therapy and ultrasound therapy. The primary outcome measure is the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire score after 6 months. Secondary endpoints are changes in pain, quality of life, disability progression, and changes of hand function. Safety will also be assessed. Discussion: Clinical data suggest that multimodal hand therapy may improve functionality and reduce pain in rhizarthrosis. Clinical data regarding therapeutic ultrasound are not available. Clinical evidence is lacking. This study is the first clinical study investigating the effects of multimodal hand therapy in direct comparison to therapeutic ultrasound and to a combination therapy with both hand therapy and ultrasound therapy for rhizarthrosis.