Rhizarthrosis – colloquially called thumb saddle joint arthrosis – (synonyms: Basic osteoarthritis; carpometacarpal osteoarthritis; thumb osteoarthritis; saddle joint osteoarthritis; ICD-10 M18.-: Rhizarthrosis [osteoarthritis of the thumb saddle joint]) is a degenerative disease of the thumb saddle joint (carpometacarpal joint I). This is located between the Os metacarpale I (first metacarpal bone; carries the thumb) and the Os trapezium (carpal bone/large polygonal bone). Rhizarthrosis refers to wear and tear of the articular cartilage.
Normally, the cartilage, together with the synovial fluid (synovial fluid), protects the joints and acts as a kind of “shock absorber”. Due to arthrosis, this function can no longer be guaranteed.
Rhizarthrosis can be divided into “primary forms” – e.g., due to overuse – and “secondary forms” – due to malformations, diseases, trauma (injuries), surgery, etc:
- Primary rhizarthrosis – bilateral (ICD-10 M18.0).
- Other primary rhizarthrosis (ICD-10 M18.1)
- Posttraumatic rhizarthrosis – bilateral (ICD-10 M18.2)
- Other post-traumatic rhizarthrosis (ICD-10 M18.3)
- Other secondary rhizarthrosis – bilateral (ICD-10 M18.4)
- Other secondary rhizarthrosis (ICD-10 M18.5)
- Rhizarthrosis, unspecified (ICD-10 M18.9)
Often both hands are affected at the same time.
Rhizarthrosis is one of the rarely occurring forms of arthritis (4%), but is the most common form of arthritis of the hand. Often there is a combination with arthroses of other finger joints as well as large body joints (polyarthrosis).
Sex ratio: males to females is 1: 10-15. One suspected cause is hormonal changes during menopause, as the onset of rhizarthrosis is usually during menopause (the time of the last spontaneous menstrual period in a woman’s life). Beyond menopause, as many as one in three to four women are affected.
Frequency peak: The disease occurs predominantly after the age of 50.
The prevalence (disease incidence) is 15% in women and 7% in men (in the group over 50 years of age).
Course and prognosis: The onset of rhizarthrosis is usually insidious. As it progresses, the joint becomes more and more deformed. Grasping becomes more difficult. If left untreated, the hand can no longer bear weight in the final stage. The disease is not curable, but adequate treatments can significantly alleviate symptoms and prevent progression (progression).
