STT osteoarthritis (scaphotrapeziotrapezoidal osteoarthritis)

Anatomy: What is the STT joint?

The STT joint consists of three carpal bones: the scaphoid (scaphoid), the trapezium (large polygonal bone) and the trapezoid (small polygonal bone). Together they form the radial column of the carpus. This partial joint transfers forces from the thumb (e.g. when grabbing or pinching) into the wrist and forearm.

• Location: on the thumb side, directly below the ball of the thumb and radially on the wrist
• Function: Stabilization of the radial carpus, power transmission when gripping
• Neighborhood: Thumb saddle joint (trapezium–1st metacarpal), scapholunate joint, radiocarpal joint

The close spatial proximity explains why complaints from the STT joint are often confused with rhizarthrosis or other carpal diseases.

What is STT osteoarthritis?

STT osteoarthritis refers to the degenerative wear of cartilage in the scaphoid-trapezium-trapezoid composite. Typical symptoms include start-up pain, pain under radial support, pinching and rotational movements (e.g. opening the lid). Over time, bony attachments (osteophytes) and joint space narrowing can occur.

• Frequency profile: less common than rhizarthrosis, but not uncommon as an incidental finding on x-rays
• Side distribution: often dominant in the strong hand
• Concomitant diseases: rhizarthrosis, unstable wrist kinematics, radiocarpal or midcarpal arthrosis

Causes and risk factors

• Age and natural wear and tear of cartilage
• Repeated mechanical stress (e.g. manual activities, sports with strong pinch loads)
• Morphological factors: scaphoid shape, axial position, ligament laxity
• Consequences of injuries: bruised carpals, ligament injuries, malunions
• Connection with rhizarthrosis: increased biomechanical stress on the radial column

Not every radiological wear change is painful. The clinical correlation is crucial: pain, functional impairment and findings must match.

Symptoms: How do you recognize STT osteoarthritis?

• Location: thumb-side wrist pain, often slightly distal to the radius
• Pain provocation: strong pinch, screwing/opening glasses, supporting in radial deviation, wrist extension
• Pressure pain over the STT joint (radial carpus, below the ball of the thumb)
• Sometimes swelling, stiffness under strain, occasionally rubbing noises (crepitation)

Other causes of radial wrist pain must be distinguished, such as de Quervain's tendovaginitis, rhizarthrosis, scapholunate ligament instability, radiocarpal osteoarthritis, bony injuries or, rarely, circulatory disorders of individual carpal bones.

When should I seek medical advice?

• Persistent pain for several weeks despite rest
• Significant reduction in hand function or strength
• After injury: persistent pressure pain, swelling, restricted movement
• Pain at rest at night, increasing deformity
• Numbness, tingling, temperature or color changes in the hand

Diagnostics: This is how we proceed

Diagnosis is based on careful clinical examination and targeted imaging. It is important that the pain actually comes from the STT joint - because there are often several potential sources of pain next to each other.

• Medical history: stress profile, professional and sporting activities, previous injuries
• Clinical presentation: tenderness on palpation over the STT joint, pain with radial deviation/extension and strong pinch
• Differential tests: Finkelstein test (de Quervain), Watson test (scapholunary) for differentiation
• X-ray: standardized levels; Oblique/oblique images can better show the STT joint
• CT: detailed bony assessment (osteophytes, subchondral sclerosis, congruence)
• MRI: evaluation of cartilage, bone marrow edema, associated ligament lesions; Exclusion of rare necrosis
• Diagnostic infiltration: targeted anesthesia of the STT joint (ultrasound-controlled) to localize pain

The targeted diagnostic injection is particularly helpful when multiple joints appear to be affected on X-ray, but it is clinically unclear which one is actually painful.

Conservative treatment – ​​the first step

The aim is to relieve pain, calm inflammation and improve function. In many cases, the symptoms can be significantly alleviated through a structured conservative program.

• Activity adjustment: Avoidance of longer radial support, tools with larger handle diameters, aids for opening jars
• Orthosis/Splint: Thumb-wrist orthosis (long opponens) for immobilization during stress phases; time-limited use
• Medication: anti-inflammatory painkillers (e.g. NSAIDs) short-term; local NSAID gels as an option
• Hand therapy/occupational therapy: joint-friendly technique, proprioceptive training, stabilization of the wrist (including ECU/FCR control), stretching and strengthening programs
• Physical: Cryotherapy in acute phases, warming measures for chronic stiffness
• Workplace ergonomics: mouse/trackball alternatives, padding, break management

The duration of conservative therapy depends on the symptoms and everyday requirements. A realistic period to assess effects is 6-12 weeks with regular follow-up.

Injections and regenerative procedures: what makes sense?

Infiltrations can specifically reduce pain - but they do not replace the treatment of the cause and are no guarantee of long-term freedom from symptoms. Indication, technique and accompanying measures are considered individually.

• Cortisone injection: may temporarily reduce inflammation and pain in the STT joint; if necessary and with limited repetition, if possible with image support
• Local anesthetic diagnostics: short-term freedom from pain as confirmation of the origin of the pain
• Hyaluronic acid: mixed evidence for small carpal joints; Off-label depending on the findings
• Autologous blood/PRP: so far only limited data for STT osteoarthritis; if necessary in individual cases and after informed consent

Important: Every injection carries risks (e.g. infection, irritation). We discuss the benefits and possible side effects transparently in advance.

Surgical options – when conservative is not enough

Operations are considered if significant pain and functional limitations persist despite consistent conservative measures. The choice of procedure depends on the extent and location of the wear, accompanying pathologies (especially rhizarthrosis, ligament instability) and your functional requirements.

• Distal scaphoid resection (open or arthroscopic): removal of the scaphoid part of the joint to reduce pain; partly with capsule/tendon interposition. Advantage: Maintains mobility. Risk: potential change in carpal kinematics; careful indication is required.
• STT arthrodesis (fusion of the scaphoid–trapezium–trapezoid): The aim is to relieve pain by immobilizing the painful joint complex. Disadvantages: prolonged immobilization, risk of nonunion, certain loss of movement.
• Trapeziectomy for combined rhizarthrosis: with dominant thumb saddle joint osteoarthritis; sometimes combined with partial trapezoid resection if the STT portion is also affected.
• Selective wrist denervation: pain-modulating procedure in selected cases without the need for axis correction.

After STT arthrodesis, immobilization in a cast/splint for several weeks is common. After distal scaphoid resection, there is usually a shorter period of immobilization with early functional therapy. We plan the follow-up treatment individually and closely accompanied by hand therapy.

Course, forecast and expectations

The course of STT osteoarthritis is variable. Many patients benefit from a combination of activity adjustment, targeted splinting during periods of stress and hand therapy. Injections can relieve pain. Surgical procedures aim to reliably reduce pain, but are associated with healing times and sometimes moderate loss of movement.

• The aim is to achieve a level of everyday functionality with little pain - not necessarily freedom from symptoms under maximum load.
• Ability to work: dependent on activity and procedure; Office work is often possible earlier than manual work.
• Sport: gradual build-up, adjustments that are gentle on the joints, if necessary splint support in the transition phase.

Everyday tips and prevention

• Use extended handles (ergo handles, kitchen aids) to reduce pinching forces
• Plan for breaks and changes in hand positions
• Train your forearm and wrist muscles in a balanced manner (therapeutically guided)
• Modify radial support positions in sports (e.g. adapt support technique in yoga)
• Take early symptoms seriously and initiate conservative measures in a timely manner

Differential diagnoses: What else is possible?

• Rhizarthrosis (thumb saddle joint)
• Quervain's tendovaginitis
• Unstable wrist kinematics (e.g. scapholunate ligament insufficiency)
• Radiocarpal or midcarpal osteoarthritis
• Nonunion after scaphoid fracture
• Rare circulatory disorders: Preiser's disease, Kienböck's disease
• Nerve constriction/neuralgia (e.g. superficial branch of the radial nerve)

Our approach in Hamburg

As an orthopedic specialist practice in Hamburg, we value clear, step-by-step diagnostics and conservative therapy as the standard approach. If necessary, image-supported diagnostic and therapeutic infiltrations are carried out using ultrasound guidance. Surgical options are discussed responsibly and only after conservative measures have been exhausted - with a transparent risk-benefit assessment and individual follow-up treatment planning.

We would be happy to provide you with differentiated advice, especially in the case of combined findings such as simultaneous rhizarthrosis or ligament instability, in order to develop a suitable, everyday-oriented treatment concept.