Diseases that have implications for the thumb impact its function, and consequently, people occupational performance. Carpometacarpal joint (CMC) thumb degeneration translates into osteoarthritis (OA). Joint congruence, ligament integrity and compression of the joint surfaces caused by muscle contraction have historically been considered the three basic pillars for carpus stability. In recent years, a new factor has been proposed to explain carpal stabilization mechanisms: proprioception. The dorsal ligament complex is the structure with the highest concentration of mechanoreceptors, especially Ruffini's corpuscles. This study aims to detect the effect of proprioceptive training on the functional recovery of people with CMC osteoarthritis in conservative treatments.

The carpometacarpal joint (CMC) of the thumb presents a paradoxical relationship between mobility and stability that confers it a high mechanical complexity, and it is continuously subjected to great efforts and repetitive movements during its use that lead to degenerative changes in susceptible individuals. The thumb CMC join degeneration results in osteoarthritis (OA).

Joint congruence, ligament integrity, and compression of the articular surfaces caused by muscle contraction have historically been considered the three basic pillars for carpal stability. In recent years, a new factor has been proposed to explain carpal stabilization mechanisms: proprioception. All afferents originating from the thumb mechanoreceptors constitute thumb proprioception. The dorsal ligament complex is the structure with the highest concentration of mechanoreceptors, especially Ruffini's corpuscles.

Classically, in conservative treatments, orthotic positioning is paramount. This study aims to detect the effect of proprioceptive training on the functional recovery of people with CMC osteoarthritis, from the comparison of a classic conservative orthotic treatment protocol vs. a conservative orthotic treatment protocol including exercises for proprioceptive training.

A randomized clinical trial is proposed within a multicenter study involving the Clínica Universitaria Reina Fabiola, Argentina and the Centro Tecan. Clínica de la Mano, Spain. The patients will be randomized into a control group that will receive orthosis treatment; and an experimental group that will also receive a home proprioceptive exercise program. Pain will be evaluated with the Visual Analogue Scale; functional capacity with the Australian Canadian Osteoarthritis Hand Index Version Functional Subscale; Occupational Productivity Performance with the Canadian Measure of Occupational Performance; and proprioception with the Joint Position Sense Test. Follow up: at 30 days and at 90 days. 50 patients will participate.

Inclusion Criteria:

• Diagnosis of grade I, II or III thumb CMC joint OA in their dominant hand according to the Eaton Classification Stage
• Pain rating of 4/10 on the Visual Analogue Scale (VAS) during activities of daily living (ADLs) at the time of the therapy initial evaluation.
• The ability to read and understand the patient information sheets and exercises.
• A minimum thumb abduction capacity of 40º.

Exclusion Criteria:

• Previous hand and wrist surgeries, neurological disorders, diagnosis of OA that includes the wrist, rheumatoid arthritis, or any implication of an osteomyoarticular nature in the hand and / or wrist other than the CMC OA.
• Had received specific treatment for hand or thumb pain in the same limb in the last 6 months including an intra-articular joint injection to wrist, fingers, or thumb.

People with carpometacarpal osteoarthritis of the thumb who require conservative treatment.