Tendon Sheath Mass: Association with Rheumatoid Arthritis
A tendon sheath mass is most commonly associated with rheumatoid arthritis (RA), presenting as tenosynovitis with swelling and pain predominantly affecting the hands and feet. 1, 2
Primary Chronic Condition
Rheumatoid arthritis is the principal chronic inflammatory disease causing tendon sheath involvement, characterized by synovial proliferation that extends to tendon sheaths, bursae, and joints. 1, 2 This manifests as:
- Tenosynovitis with palpable swelling and tenderness along tendon sheaths, particularly in the hands (metacarpophalangeal joints, wrists) and feet (metatarsophalangeal joints) 1, 2
- Symmetric distribution of tendon involvement, which is a hallmark feature distinguishing RA from other conditions 2, 3
- Morning stiffness lasting at least 1 hour before maximal improvement, directly related to disease activity 2
Distinguishing Features from Other Conditions
The pattern of tendon sheath involvement in RA differs significantly from other causes:
- RA tenosynovitis shows intratendinous signal alterations without significant tendon enlargement (90% of cases have normal anteroposterior diameter) 4
- Associated retrocalcaneal bursitis is present in all RA patients with Achilles tendon involvement, unlike degenerative tendinopathy 4
- Multiple symptomatic tendons should prompt immediate evaluation for rheumatic disease, as this pattern is uncommon in isolated degenerative or traumatic tendinopathy 5
Diagnostic Approach
When encountering a tendon sheath mass, evaluate for RA by:
- Testing for rheumatoid factor and anti-CCP antibodies, which are present in >70% of patients who develop erosive disease 1, 3
- Assessing for symmetric joint involvement in small joints of hands and feet 2, 3
- Measuring acute phase reactants (ESR, CRP) which correlate with disease activity and radiographic changes 2
- Ultrasonography to visualize synovial thickening within tendon sheaths and joints, even in early disease 6, 2
Alternative Chronic Conditions
While RA is the primary association, other chronic conditions causing tendon sheath masses include:
- Spondyloarthropathies (presenting as enthesitis at tendon insertion sites rather than tenosynovitis along the sheath) 6, 1
- Nontuberculous mycobacterial infections (particularly M. marinum and MAC causing chronic granulomatous tenosynovitis of the hand after direct inoculation) 6
- Crystal deposition diseases (gout with tophi, though these typically present as periarticular masses rather than true tenosynovitis) 6
Critical Clinical Pitfall
Do not dismiss a tendon sheath mass as simple degenerative tendinopathy if multiple tendons are involved or if there is symmetric distribution—this pattern mandates rheumatologic evaluation. 5 Degenerative tendinopathy typically causes tendon enlargement (>8mm anteroposterior diameter) without the intratendinous signal changes and bursal inflammation characteristic of RA. 4