Rhizarthrosis (arthrosis of the thumb saddle joint)

Anatomy and function of the thumb saddle joint

The thumb saddle joint is a movable saddle joint between the trapezium and the first metacarpal bone. It allows opposition, abduction, adduction and rotation - movements that enable precise gripping, pinching and holding. It is stabilized by complex ligament guidance and the surrounding muscles.

• Important tapes: v. a. the palmar (beak/bundle) ligament and dorsoradial ligament
• Muscular stabilizers: M. abductor pollicis longus/brevis, M. opponens pollicis, M. adductor pollicis
• High strain during pinch and pincer grips leads to increased joint pressure

Repeated peak loads and age-related changes can cause the cartilage to wear down. This results in flare-ups of inflammation (synovitis), loosening of the capsule and ligaments, and bony attachments (osteophytes).

What is rhizarthrosis?

Rhizarthrosis is a progressive wear of cartilage in the saddle joint of the thumb. The cartilage loses its ability to glide, the joint space narrows and friction, inflammation and pain occur. Over time, misalignments such as the so-called Z deformity of the thumb can occur.

• Early stages: exercise-related pain, temporary swelling
• Advanced stages: pain at rest, loss of strength, bony remodeling
• Final stages: significant restriction of movement and deformity

Symptoms: How do I recognize rhizarthrosis?

• Pain on the ball of the thumb and radial wrist, increased with pinch/pincer grips
• Difficulty opening bottles/jars, turning keys, writing
• Morning stiffness, exercise-related swelling and warmth
• Clicking or rubbing noises (crepitation) in the joint
• Loss of strength, unsteady grip, possibly visible misalignment (Z deformity)
• Pressure pain over the saddle joint of the thumb, positive grind test

A gradual increase in symptoms over months to years with episodic inflammatory attacks is typical.

Causes and risk factors

• Age and gender: common in postmenopausal women
• Ligament laxity/hypermobility of the thumb saddle joint
• Repetitive overload (work, household, sports, musical instruments)
• Previous injuries (e.g. fractures, ligament injuries)
• Concomitant arthroses (e.g. STT joint), inflammatory rheumatic diseases
• Genetic factors and anatomical variants

Diagnostics: Examination and imaging

Diagnosis is based on history, physical examination and, if necessary, imaging. The aim is to precisely identify the source of the pain and rule out differential diagnoses.

• Clinical tests: grind test (compression-rotation test), stability test, palpation pain
• Functional testing of pinch/pincer grip, opposition and strength
• X-rays in standardized planes to assess joint space, osteophytes, subluxation
• Ultrasound to assess synovitis; MRI is rarely necessary if the findings are unclear
• Differential diagnoses: de Quervain's tendovaginitis, STT osteoarthritis, radiocarpal/midcarpal osteoarthritis, scaphoid problems (e.g. Preiser's disease), carpal tunnel syndrome

Imaging is used for staging and surgical planning, but treatment is primarily based on symptoms and functional impairment.

Conservative therapy: gentle and close to everyday life

In the early and middle stages, conservative therapy is the most important component. It can reduce pain, reduce inflammation and improve function. The goal is the best possible resilience in everyday life.

• Activity adjustment: Avoid load peaks (e.g. heavy screw caps), use aids
• Orthosis/splint (CMC-I orthosis, opposition splint) for temporary immobilization and stabilization
• Physio/occupational therapy: joint protection, manual techniques, targeted strengthening of the thenar muscles
• Self-exercises and ergonomic training (see below)
• Heat/cold according to individual tolerance; topical anti-rheumatic drugs
• Short-term use of non-steroidal anti-inflammatory drugs (NSAIDs) after consultation with a doctor
• Taping to support stability during periods of stress

Conservative measures are often used in combination. Consistent implementation over several weeks is crucial before deciding on the next steps.

Injection therapies: possibilities and limitations

Injections can be a useful supplement if splints, training and painkillers do not help sufficiently. However, they do not replace basic therapy and their effect is limited in time.

• Cortisone injection: can relieve inflammation and pain for weeks to a few months; limit number per year; preferably ultrasound targeted
• Hyaluronic acid: The aim is a viscosupplementation; The study situation is heterogeneous, the effect varies from person to person
• PRP (autologous blood plasma): experimental or inconsistent evidence; only after informed consent and an individual benefit-risk assessment
• General risks: temporary increase in pain, bruising, infection (rare), tendon/ligament irritation

Which option is suitable depends on the stage, symptoms, comorbidities and individual goals. We discuss opportunities and limitations transparently.

Surgical options: When does surgery make sense?

Surgery is considered if consistent conservative measures over several months do not provide sufficient relief and everyday function is significantly restricted. The choice of procedure depends on the stage, ligament stability, occupational stress and accompanying osteoarthritis.

• Trapeziectomy (removal of the trapezium) with or without ligament/tendon suspension (e.g. LRTI, suture button): proven procedures with high patient satisfaction
• Hematoma or interposition arthroplasty: maintaining the distance between the base of the first metacarpal and the neighboring bone
• Denervation of CMC I: selective division of pain-conducting nerve branches, joint remains intact; v. a. with pain dominance
• Arthrodesis (joint stiffening): for high load demands; stable, less painful function, but loss of movement
• Prosthesis implantation: selected cases; Long-term durability and complication rates must be considered individually

Rehabilitation: Follow-up treatment includes the splint phase, gradual mobilization and targeted strengthening. Daily activities are often possible again after 6-8 weeks; complete strength development can take 6-12 months. Complications (e.g. wound healing disorders, sensory disorders, persistent pain) are possible and will be discussed in the consultation.

Course and prognosis

Rhizarthrosis is a chronic, usually slowly progressive joint disease. Many of those affected are able to cope well with everyday life with consistent conservative therapy. In advanced stages, surgical procedures often offer significant pain relief and functional improvement - but there can be no guarantee.

• Consistently applied splint and exercise programs are effective in everyday practice
• Injections can close a gap in the symptoms in the short term
• Surgical procedures show mostly good to very good satisfaction rates in studies
• Concomitant illnesses (e.g. STT osteoarthritis, carpal tunnel syndrome) influence the course

Everyday life, joint protection and simple exercises

Small adjustments in everyday life reduce load peaks and support the healing process. Exercises should be painless, regular and dosed.

• Joint protection: wide handles, non-slip openers, distribute purchases between both hands
• Technique: use the whole hand more often instead of the pinch grip
• Workplace: ergonomic mouse/pen, short exercise intervals with breaks
• Wear the splint specifically during periods of stress; Consider taking it at night if there is a flare-up of inflammation

If pain persists, pause exercises and consult a doctor. Quality of movement is more important than number of repetitions.

Differentiation from other causes of thumb pain

• Tendovaginitis de Quervain: pain over the thumb tendon on the wrist, positive Finkelstein test
• STT osteoarthritis (scaphoid–trapezoid–trapezoid): Radial-dorsal pain, often combined with rhizarthrosis
• Radiocarpal or midcarpal osteoarthritis
• Scaphoid necrosis (Preiser's disease) or lunate necrosis (Kienböck's disease)
• Carpal tunnel syndrome (especially nighttime numbness/tingling, loss of strength)
• Post-traumatic sequelae (e.g. nonunion after fracture)

When should I seek medical advice?

• New or increasing pain and swelling on the ball of the thumb
• Pain at rest, pain at night or significant loss of strength
• Numbness, radiation in hand/fingers, feeling of instability
• After a fall/trauma, redness, overheating, fever or open injuries
• If conservative measures do not bring any improvement after a few weeks

What you can expect in our practice

We take time for anamnesis, functional analysis and understandable advice. Our focus is on gradual, conservative therapy. Injections and surgical options are only recommended if there is a clear indication and after transparent information.

Location: Dorotheenstraße 48, 22301 Hamburg. Appointments can be easily requested via Doctolib or by email.