Sometimes people talk about thumb arthritis and sometimes about rhizarthrosis…

Although these two terms are similar, they do not mean exactly the same thing.

If patients recognise the difference, it gives them a better understanding of the specifics of rhizarthrosis, so that they can spot its development and communicate more confidently with healthcare professionals.

This page forms part of the section on ‘Understanding rhizarthrosis’, together with articles on the first symptoms, the causes and diagnosis of rhizarthrosis.

Thumb arthritis: a generic term

The term thumb arthritis is often used in everyday language to refer to wear of the cartilage in one of the thumb joints.

It may refer to a number of specific areas among the three joints of the thumb, listed here from the tip to the base:

  • the interphalangeal joint: in the middle of the digit, between the two phalanges;

  • the metacarpophalangeal joint: at the base of the digit, between the first phalanx and the first metacarpal;

  • the trapeziometacarpal joint: at the base of the thumb, where it meets the wrist. : à la base du pouce, là où il rejoint le poignet.

In the vast majority of cases, wear affects the lowest joint: the trapeziometacarpal joint. And this is what is known as rhizarthrosis.

Rhizarthrosis: a very specific form of thumb arthritis

The word ‘rhizarthrosis’ comes from Greek:

  • rhiza : means root,

  • arthron : means joint,

  • and the suffix -osis indicates a pathological condition without inflammation.

Rhizarthrosis therefore refers to osteoarthritis at the base of the thumb, affecting the trapeziometacarpal joint (between the trapezium bone of the wrist and the metacarpal bone of the thumb).

It is a very common form of arthritis and is found in particular in women over the age of 50. It can also develop earlier, particularly in the event of repetitive movements or in people who are predisposed to the condition.

Characteristic signs of rhizarthrosis include the following:

  • pain at the base of the thumb (especially when the thumb is put under strain);

  • difficulty with gripping movements (opening jars, turning keys, etc.);

  • and sometimes progressive joint deformation.

Thumb arthritis or rhizarthrosis: how to distinguish between the two?

The two terms are sometimes used interchangeably in practice, but they do not mean exactly the same thing:

  • Thumb arthritis : Generic term referring to wearing away of the cartilage in any joint of the thumb

  • Rhizarthrosis : Refers specifically to arthritis of the trapeziometacarpal joint only

To sum up then, all rhizarthrosis is arthritis of the thumb, but not all arthritis of the thumb is rhizarthrosis.

Why is this distinction useful?

There are a number of advantages to knowing the difference between the two concepts:

  • If you understand your condition, you can identify the joint affected and adapt your hand movements accordingly.

  • You will be able to communicate better with healthcare professionals – certain specialists are more likely to distinguish between the two terms according to their specialist field (rheumatologists, surgeons, physiotherapists, etc.).

  • You can target the right sources of information: brochures, medical websites, consultation reports.

  • You can prepare for the right type of care: because of the part of the body affected, rhizarthrosis may require closer monitoring or specific treatment.

Remember:

  • Thumb arthritis is a broad term that can refer to various forms of joint damage.

  • Rhizarthrosis refers specifically to arthritis at the base of the thumb – a very common and potentially disabling condition.

  • If patients understand this distinction, it provides them with a better understanding of their diagnosis and the solutions available.

Further information