OBJECTIVE: To present the spectrum of pathology affecting the flexor carpi radialis (FCR), and its anatomical, functional and clinical relationship with conditions affecting the triscaphe or scapho-trapezium-trapezoid (STT) compartment, and particularly osteoarthritis. DESIGN: The study comprised two men and four women aged between 23 and 79 years (mean age, 49 years). Two musculoskeletal radiologists in consensus evaluated MRI findings. RESULTS: Five of the patients showed evidence of triscaphe osteoarthritis. One of the patients showed synovitis and reactive marrow edema at the triscaphe joint without more specific findings of osteoarthritis. Five patients showed evidence of FCR tenosynovitis. Partial-thickness tears were noted in three patients. Two patients showed complete discontinuity of the FCR; one of them had undergone prior tendon harvesting for interposition arthroplasty after trapezectomy. One patient showed a ganglion cyst in connection to the FCR tendon sheath. CONCLUSION: The FCR tendon courses over the volar surfaces of the scaphoid and trapezium in a separate fibro-osseous tunnel. This anatomical and functional relationship explains the coexistence of FCR tendinopathy and STT arthritis demonstrated by MR imaging.