Ulnar-sided wrist pain: an 8.8 mm² tendon on MRI was the dividing line
In short
A common cause of ulnar-sided (little-finger-side) wrist pain is extensor carpi ulnaris (ECU) tenosynovitis, and the tendon is enlarged when it occurs. Comparing wrist MRIs of 26 patients with 26 controls, mean ECU cross-sectional area was 10.86 mm² versus 7.25 mm², and a cutoff of 8.80 mm² gave 84.6% sensitivity, 84.6% specificity and an AUC of 0.89. Single-axis thickness performed similarly (cutoff 1.98 mm, AUC 0.88), but agreement between the two readers was higher for area (ICC 0.92 versus 0.88).
When ulnar-sided wrist pain goes to MRI, the reader is looking at how enlarged the tendon is. What this study tested is what changes when that enlargement is measured as an area rather than as a single line of thickness. Axial T1-weighted wrist MRIs from 26 patients with clinically diagnosed ECU tenosynovitis and 26 controls were read independently by two musculoskeletal radiologists blinded to the clinical information.
Where the ECU tendon sits
The extensor carpi ulnaris runs along the little-finger side of the wrist and passes through a groove at the end of the ulna. It moves inside that groove when the wrist extends and deviates toward the ulna, and when the forearm rotates. That is why pain here tends to show up under loads taken with a bent wrist, or under repeated rotational load.
What the numbers say
- Cross-sectional area — 10.86 ± 2.32 mm² in patients, 7.25 ± 2.52 mm² in controls (p < 0.001).
- Cutoff — 8.80 mm², giving 84.6% sensitivity, 84.6% specificity, AUC 0.89.
- Thickness — cutoff 1.98 mm, AUC 0.88. Diagnostic performance was essentially the same.
- Reproducibility — interobserver agreement was ICC 0.92 for area and ICC 0.88 for thickness.
The takeaway is not that the new measure is more accurate. Accuracy was comparable; what changed is that the number moves less when the reader changes. Whether the same wrist yields the same figure at a different clinic matters as much as accuracy once you are tracking a tendon over time.
What this means for a lifter
Ulnar-sided wrist pain is common in barbell training. The front rack position, the moment a kettlebell rolls over the back of the hand, a bench grip with the wrist cocked back, and reverse curls with their forearm rotation all load this tendon. The point worth holding onto is that a thicker tendon here is not a training adaptation. Muscle that gets thicker gets stronger; this thickening arrives with inflammation, and it belongs in the same category as tendons lagging behind strength gains. Wraps and tape can mask the symptom without changing the path the load takes. Changing the grip (see reverse curls and grip) or pulling rotational work for a while comes first.
This was a single-centre retrospective case-control imaging study of 26 versus 26, not a treatment trial, and the authors call for multicentre validation in larger cohorts. Wrist pain cannot be self-diagnosed from an MRI number, and pain lasting more than a few weeks needs a clinician.
Frequently asked questions
What commonly causes pain on the little-finger side of the wrist?
Extensor carpi ulnaris (ECU) tenosynovitis is one common cause. The tendon runs through a groove at the end of the ulna on the little-finger side of the wrist, and inflammation there is often accompanied by enlargement of the tendon itself.
What ECU cross-sectional area is considered abnormal on MRI?
In a study of 26 patients versus 26 controls, the optimal cutoff was 8.80 mm², giving 84.6% sensitivity, 84.6% specificity and an AUC of 0.89. Mean area was 10.86 mm² in patients and 7.25 mm² in controls.
What does measuring area add over measuring thickness?
Diagnostic performance was similar — AUC 0.88 for thickness and 0.89 for area. The difference was reproducibility: interobserver agreement was ICC 0.92 for area versus ICC 0.88 for thickness.
Does a thicker tendon mean it has gotten stronger from training?
Not in this case. The enlargement seen in ECU tenosynovitis accompanies inflammation and is used as diagnostic evidence, not as a sign of adaptation.
Is a wrist wrap enough when the wrist hurts?
Wraps and tape can reduce the symptom but do not change how load reaches the tendon. Adjusting the grip or reducing exercises with heavy forearm rotation comes first, and pain lasting more than a few weeks warrants medical assessment.
Source: PubMed