The research, published in BMC Medical Imaging, was led by Kyu-Chong Lee and Kyung-Sik Ahn of Korea University Anam Hospital in Seoul, together with colleagues from several Korean medical centers. The team set out to answer a deceptively simple question: when a shoulder MRI shows abnormalities of the joint capsule, what do those abnormalities actually mean? Adhesive capsulitis has long been associated with characteristic changes in two specific regions of the shoulder joint, the rotator interval and the axillary pouch. The rotator interval is a triangular space between the supraspinatus and subscapularis tendons through which the long head of the biceps tendon passes, while the axillary pouch is the redundant fold of capsule at the lower part of the joint that allows the arm to lift overhead. In classic frozen shoulder, both regions typically show thickening, edema, and inflammation.

To investigate, the researchers conducted a retrospective analysis of 483 adults who underwent shoulder MRI between January and December 2020. Two musculoskeletal radiologists independently reviewed each scan, assessing abnormalities in the rotator interval and the axillary pouch, as well as tears of four key tendons: the supraspinatus, the infraspinatus, the subscapularis, and the long head of the biceps tendon. The team defined radiologic capsular abnormality, abbreviated RCA, as the presence of abnormalities in both the rotator interval and the axillary pouch simultaneously. They then used univariable and multivariable logistic regression analyses to identify which clinical and imaging factors were associated with RCA, and performed subgroup analyses comparing four patient groups: those with no capsular abnormality, those with isolated axillary pouch abnormality, those with isolated rotator interval abnormality, and those with full RCA, adjusting for age where appropriate.

The headline finding was striking. Of the 483 patients studied, 234, or 48.45 percent, had radiologic capsular abnormality. In other words, nearly one in every two shoulders scanned showed the capsular changes that many radiologists and clinicians associate with frozen shoulder. Yet clinically diagnosed adhesive capsulitis was present in only 45 patients, or 9.32 percent of the cohort. Of those 45 patients, 43 did indeed have RCA, confirming that the imaging finding is sensitive for the disease. But the reverse is emphatically not true: the overwhelming majority of patients with RCA, more than four out of five, did not have a clinical diagnosis of adhesive capsulitis. The imaging finding, in isolation, is simply not specific enough to serve as a diagnosis.

The regression analyses revealed a web of associations that complicate the picture further. Older age was independently associated with higher odds of RCA, with each additional year of age raising the odds by roughly five percent, an odds ratio of 1.05 with a 95 percent confidence interval of 1.03 to 1.07 and a p-value below 0.001. This makes biological sense, since the joint capsule, like every other soft tissue in the body, undergoes degenerative change over time. A capsule that looks thickened or edematous in a 65-year-old may simply reflect the accumulated wear of decades rather than an active inflammatory disorder. Any diagnostic framework that treats capsular abnormality as synonymous with frozen shoulder must therefore account for the age of the patient, or risk labeling normal age-related change as pathology.

Tendon tears added another layer of complexity. Tears of the subscapularis tendon, one of the four muscles that make up the rotator cuff, were positively associated with RCA. Patients with Lafosse type I subscapularis tears, the mildest grade, had 1.82 times the odds of RCA compared with those without such tears, while those with type II or higher tears had 2.15 times the odds, both statistically significant results. The long head of the biceps tendon, which runs directly through the rotator interval, also emerged as relevant: in subgroup analyses, isolated rotator interval abnormality was associated with a higher prevalence of both subscapularis and biceps tendon tears than no capsular abnormality, even after adjusting for age. This suggests that inflammation or degeneration in the rotator interval often reflects pathology of the tendons that traverse it, rather than a primary capsular disease.

Perhaps most intriguingly, tears of the supraspinatus and infraspinatus tendons, the two most commonly torn rotator cuff tendons, showed the opposite relationship: they were negatively associated with RCA. Patients with these tears were less likely to show capsular abnormalities than patients without them. The authors interpret this finding as consistent with the traditional concept of adhesive capsulitis as a diagnosis of exclusion, a condition diagnosed only after other shoulder pathologies have been ruled out. In practical terms, a shoulder dominated by a large supraspinatus or infraspinatus tear appears less likely to harbor the capsular changes of frozen shoulder, perhaps because the two conditions represent distinct biological processes that do not readily coexist, or because the mechanical picture of a cuff tear overshadows and excludes the capsular one.

The clinical implications of the study are considerable. If nearly half of shoulder MRI scans show capsular abnormalities but only about nine percent of patients have frozen shoulder, then any radiology report that flags capsular abnormality without careful qualification invites overdiagnosis. A patient told that their MRI shows findings consistent with adhesive capsulitis may undergo months of stretching programs, corticosteroid injections, or even capsular distension procedures that address the wrong problem, while the true culprit, perhaps a subscapularis tear or biceps tendon pathology, goes untreated. The authors argue that the term radiologic capsular abnormality itself should be used in reports, precisely because it describes an imaging observation without asserting a clinical diagnosis, and that particular caution is warranted in older patients and in those with subscapularis or biceps tendon pathology.

The study does have limitations inherent to its design. It was retrospective, drawing on patients who had already been referred for shoulder MRI at a single Korean institution, which may limit generalizability to other populations. The clinical diagnosis of adhesive capsulitis was extracted from existing records rather than standardized prospectively, and the researchers note that the article was published initially as an early citable version subject to further edits. Still, the size of the cohort, the independent double reading by two musculoskeletal radiologists, the multivariable statistical framework, and the age-adjusted subgroup analyses give the findings substantial weight. The work was supported by a grant from the National Research Foundation of Korea, and the authors declared no competing relationships with companies whose products might relate to the subject matter.

For patients and clinicians alike, the message is ultimately one of humility about what imaging can and cannot tell us. MRI is a magnificent tool for revealing the anatomy of the shoulder in exquisite detail, but anatomy is not destiny, and a thickened capsule on a scan is a finding, not a verdict. Frozen shoulder remains a clinical diagnosis, rooted in a patient’s history of progressive pain and profound restriction of both active and passive motion, and it should be confirmed by examination rather than inferred from a radiology report. As this study makes clear, the capsule that lights up on MRI may be telling a story about age, about a torn subscapularis tendon, or about an inflamed biceps pulley, and only careful clinical correlation can determine which story is true. In an era when imaging findings increasingly drive diagnostic decisions, the humble conclusion that a scan must never replace the physical examination has rarely been more vividly illustrated.

Subject of Research: Radiologic capsular abnormalities on shoulder MRI and their association with rotator cuff and biceps tendon tears in the diagnosis of adhesive capsulitis

Article Title: Radiologic capsular abnormalities on shoulder MRI: associations with rotator cuff and biceps tendon tears and implications for the diagnosis of adhesive capsulitis

Article References: Radiologic capsular abnormalities on shoulder MRI: associations with rotator cuff and biceps tendon tears and implications for the diagnosis of adhesive capsulitis. (n.d.). https://doi.org/10.1186/s12880-026-02895-y

Image Credits: AI Generated

DOI: 10.1186/s12880-026-02895-y

Keywords: shoulder MRI, adhesive capsulitis, frozen shoulder, rotator cuff tear, subscapularis tendon, biceps tendon, rotator interval, axillary pouch, radiologic capsular abnormality, musculoskeletal radiology, overdiagnosis, BMC Medical Imaging

The research, led by Oguzhan Ekizoglu together with Marine Dario, Maxime Pastor, Catherine Cyteval, and Laurent Martrille, focused on a bone that has been comparatively neglected in the MRI-based age estimation literature: the proximal humerus, the ball-shaped top of the upper arm bone. While the hand-wrist region and the knee have been extensively mapped with MRI for forensic purposes, the shoulder has received far less systematic attention, particularly in Western European populations. The team retrospectively analyzed 346 shoulder MRI examinations drawn from a French cohort spanning the ages of 7.18 to 33.82 years, comprising 204 males and 142 females. Because the scans had been acquired for clinical reasons and were fully anonymized, the ethics committee of CHU Montpellier approved the study and waived the need for individual informed consent, an approach consistent with the Declaration of Helsinki.

The technical backbone of the study is the combined Schmeling–Kellinghaus staging system, a widely used framework originally developed for the medial end of the collarbone. In this system, ossification of the epiphysis, the secondary growth center that fuses to the main bone shaft after puberty, is graded in discrete stages, from an entirely cartilaginous growth plate through progressive partial fusion to complete union, with an optional subdivision for the earliest signs of fusion. On T1-weighted MRI sequences, the developing bone and the cartilaginous plate between epiphysis and metaphysis produce distinct signal intensities, allowing a trained observer to assign each shoulder to a stage. Two independent raters, blinded to each subject’s age and sex, staged all 346 scans, providing a direct test of how reproducible the method is when applied to the humeral head.

The results were strikingly consistent. The correlation between chronological age and ossification stage was strong and statistically significant across the whole sample, with a Spearman’s rank correlation coefficient of 0.878, and nearly identical values of 0.880 in males and 0.878 in females, all with p-values below 0.001. In practical terms, this means that as the humeral epiphysis progresses through its developmental stages, age increases in a tight, predictable relationship, and that this relationship holds equally well for both sexes. Statistical testing with the Mann–Whitney U method found no significant difference between males and females in the ages associated with any given stage, a finding that simplifies the application of the system, since a single set of stage descriptions may suffice for both sexes in this population.

Reliability, the measure of whether different observers reach the same conclusion from the same image, was equally impressive. Cohen’s kappa, a statistic that quantifies agreement beyond what would be expected by chance, reached 0.911 within observers rating their own scans twice and 0.890 between the two independent raters. Values above 0.8 are conventionally considered to indicate very good agreement, and these figures place the proximal humerus staging on par with, or better than, many established forensic imaging indicators. For a method that might one day inform legal decisions with life-changing consequences, this level of observer agreement is not a technical nicety but an essential prerequisite, because inconsistent readings between experts would undermine the credibility of any age estimate offered in court.

The most legally consequential finding concerns the age of majority, the threshold at 18 years that separates minors from adults in most jurisdictions. In this cohort, the youngest individual showing stage 4, defined by the presence of a visible epiphyseal scar after fusion, was 18.33 years in males and 18.06 years in females. In other words, once the epiphyseal scar is visible on the proximal humerus, the data suggest the person has very likely passed their eighteenth birthday. Notably, stage 5, the final stage of the amplified scheme, was never observed despite the cohort including individuals up to nearly 34 years of age, an observation the authors interpret in light of the persistent visibility of the epiphyseal scar in adult shoulders and the anatomical characteristics of trabecular bone in this region.

Beyond the conventional minimum-age approach, the team applied an ordinal probit transition analysis, a statistical framework borrowed from paleodemography that models the probability of moving from one ossification stage to the next as a function of age. Rather than relying on the single youngest individual observed at a stage, a figure that is highly sensitive to how many older or younger people happen to be in the sample, transition analysis yields sex-specific ages at which the probability of progression to the next stage reaches 50 percent. This provides a more statistically robust characterization of the timing of skeletal maturation and has been increasingly advocated in forensic age research, including recent work on third molars and other skeletal indicators. The authors are careful, however, to stress that both minimum-age and transition-age estimates derived from any single cohort should not be applied as forensic thresholds without independent, population-specific validation, a caution that reflects the well-documented variation in skeletal maturation across populations and socioeconomic conditions.

Perhaps the most original contribution of the study is the description of a previously unreported interpretive pitfall. The authors identified a trabecular hypointense pattern, a dark appearance of the internal bone architecture on T1-weighted images, that can potentially mimic a persistent gap between the epiphysis and the metaphysis, the appearance that would normally indicate an unfused, and therefore juvenile, growth plate. Mistaking this normal variant for an open growth plate could lead an examiner to underestimate a person’s age, with serious implications in asylum or criminal proceedings. The paper includes recommendations for recognizing this pattern, underscoring that even a highly reliable staging system depends on the examiner’s ability to distinguish true developmental landmarks from imaging artifacts and anatomical variants of the cancellous bone in the proximal humerus.

The broader context of this work is a slow but decisive shift in forensic practice. European radiation protection directives and international basic safety standards from bodies such as the International Atomic Energy Agency have sharpened the ethical and legal scrutiny applied to X-ray-based age assessments in healthy young people, pushing researchers toward MRI as a non-ionizing alternative. Previous MRI studies of the proximal humeral epiphysis, including earlier work by Ekizoglu and colleagues on Turkish cohorts and studies from China and Turkey using both 1.5 and 3.0 Tesla scanners, have demonstrated the promise of the approach, but population-specific data remained sparse for Western Europe. By extending the combined Schmeling–Kellinghaus system to a French cohort for the first time, the Montpellier team has filled an important geographic gap and shown that the staging framework travels well across populations, at least in terms of correlation strength and observer reliability.

What remains before shoulder MRI can enter routine forensic use is a matter of validation and standardization rather than proof of concept. Large, independently collected cohorts from different populations will be needed to confirm the minimum ages and transition probabilities reported here, and the newly described trabecular pitfall will need to be characterized across scanner types and imaging protocols. Cost and scanner availability also remain practical constraints, since MRI is more expensive and less widely accessible than plain radiography. Nevertheless, the study offers a compelling vision of the field’s future: a radiation-free, highly reproducible, and anatomically well-characterized method for answering one of forensic science’s most sensitive questions. For the hundreds of thousands of young people whose ages are contested each year in legal systems worldwide, the humeral head, imaged safely with magnets rather than X-rays, may soon become a key witness.

Subject of Research: Non-ionizing forensic age estimation using T1-weighted MRI of the proximal humeral epiphysis in a French cohort

Article Title: T1-Weighted MRI of the proximal humerus: Toward a non-ionizing approach to forensic age estimation in a French cohort

Article References: Ekizoglu, O., Dario, M., Pastor, M., Cyteval, C., & Martrille, L. (2026). T1-Weighted MRI of the proximal humerus: Toward a non-ionizing approach to forensic age estimation in a French cohort. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-03996-7

Image Credits: AI Generated

DOI: 10.1007/s00414-026-03996-7

Keywords: forensic age estimation, MRI, proximal humerus, epiphyseal fusion, Schmeling-Kellinghaus staging, age of majority, transition analysis, non-ionizing imaging, forensic medicine, immigration, radiation protection, French cohort