Ultrasound and CT reveal silent bone changes in psoriasis before arthritis

Psoriasis is often described as a skin condition, but a growing body of research treats it as a systemic inflammatory disease whose effects can reach far beneath the surface of the skin. A new case-control study published in Egyptian Rheumatology and Rehabilitation examined people with psoriasis who showed no clinical signs of psoriatic arthritis, and found that a substantial proportion of them already carried measurable structural changes in the small bones of the hand. Using two complementary imaging techniques, the researchers detected erosions and bony outgrowths at rates far above those seen in healthy controls, and they observed that patients treated with biological therapies tended to show fewer of these changes than patients on conventional treatment.

The study, led by Heba Elsayed Elshok and colleagues, enrolled 50 patients with psoriasis and 25 healthy controls matched for age, sex, and body mass index. The patients were divided into two equal groups: one receiving conventional therapy and one receiving biological therapy, which typically targets inflammatory signalling molecules such as tumour necrosis factor or interleukin-17. All participants underwent a detailed clinical and laboratory assessment, musculoskeletal ultrasound of the joints and entheses, and high-resolution computed tomography of the dominant hand. The researchers deliberately excluded anyone with psoriatic arthritis, other inflammatory joint disease, diabetes, hand osteoarthritis, or a history of hand trauma or surgery, so that the imaging findings would reflect truly subclinical changes rather than established joint disease.

The choice of imaging modality matters. Musculoskeletal ultrasound is a sensitive, non-invasive technique capable of revealing synovitis, tenosynovitis, and enthesitis that never appear on a routine clinical examination. Enthesitis, the inflammation at the points where tendons and ligaments anchor to bone, is considered a central pathological feature in the development of psoriatic arthritis, and subclinical entheseal involvement has been repeatedly reported in psoriasis patients who have no musculoskeletal symptoms at all. High-resolution computed tomography, meanwhile, adds a different dimension: it can visualise early structural bone abnormalities, including erosions and enthesophytes, that may precede clinically apparent arthritis. In this study, the CT protocol focused on the second and third metacarpophalangeal joints of the dominant hand, sites chosen because they are biomechanically stressed and known from earlier research to show the earliest signs of subclinical bone remodelling in psoriatic disease.

The results were striking. Bone erosions visible on CT were present in 44 percent of the conventionally treated group, 28 percent of the biologically treated group, and just 4 percent of healthy controls, a difference that reached statistical significance. Enthesophytes, bony outgrowths at tendon or capsular insertions, were even more common: 76 percent of the conventional group carried at least one, compared with 44 percent of the biological group and 8 percent of controls. Multiple enthesophytes were also far more frequent in the conventional group, appearing in 44 percent of those patients versus 16 percent of the biological group and none of the controls. The distribution of these outgrowths varied significantly across anatomical sites, particularly at the second and third metacarpal heads.

Ultrasound told a partially consistent story. The total ultrasound score was higher in the conventional group than in the biological group and controls, but this difference did not reach statistical significance. When the authors calculated effect sizes and confidence intervals for these non-significant trends, they found a small measurable difference favouring the biologically treated patients, and grey scale synovitis showed a borderline trend suggesting less synovial thickening in that group. The authors caution that these ultrasound findings should be read as low-grade subclinical inflammation rather than overt disease, and the statistical analysis was designed to contextualise rather than overstate them.

One of the most interesting threads in the data concerns the relationship between skin severity and musculoskeletal change. The Psoriasis Area and Severity Index, or PASI, correlated positively with several ultrasound measures, including grey scale synovitis, a global inflammatory subscore, and the total ultrasound score, all with correlation coefficients around 0.57 to 0.59 and p values below 0.001. PASI also correlated with the number and height of enthesophytes seen on CT. In addition, PASI correlated with age, body mass index, age of disease onset, erythrocyte sedimentation rate, and C-reactive protein, and it correlated negatively with several quality-of-life measures from the SF-36 questionnaire, including pain and overall score. Taken together, these correlations suggest that skin disease severity and subclinical musculoskeletal involvement travel together, a link that other studies have also observed, although the literature is not entirely uniform on this point.

Perhaps the most provocative finding is the apparent inverse relationship between disease duration and structural damage across the two treatment groups. Patients on biological therapy had actually lived with psoriasis significantly longer, an average of 10.01 years versus 5.65 years in the conventional group, yet they showed fewer erosions and enthesophytes. Because bone damage generally accumulates over time, the authors argue that this pattern lends weight to the idea that biological therapy may be associated with a lower burden of subclinical structural change. In regression analysis, treatment type emerged as an independent factor associated with the presence of enthesophytes, and the total ultrasound score predicted both erosions and enthesophytes on CT. The researchers are careful, however, to frame these results as associations rather than proof of causation, noting that the observational case-control design cannot establish a causal link between therapy and bone outcomes.

The study has other limitations worth keeping in view. It was conducted at a single centre with a relatively small sample, and the authors acknowledge that differences in disease duration and in the specific biologic agents used among patients may have influenced the imaging results. Laboratory markers of inflammation, including erythrocyte sedimentation rate, C-reactive protein, and rheumatoid factor, showed no differences across the three groups, which the authors attribute in part to the limited sensitivity of these markers in psoriatic disease. The ultrasound examinations were performed by a single experienced radiologist and the CT images by a blinded independent reader, which strengthens internal consistency but does not substitute for the broader generalisability that larger, multi-centre longitudinal studies would provide.

What the study does offer is a clearer picture of the silent phase that may precede psoriatic arthritis. Psoriasis affects roughly 2 to 3 percent of the population, and psoriatic arthritis develops in nearly 30 percent of those patients, sometimes causing progressive joint damage when it goes unrecognised. Because psoriasis typically precedes arthritis by several years, researchers have long suspected a window in which inflammatory and structural changes are already underway but symptoms have not yet appeared. The present findings support that idea: structural remodelling was detectable in a significant proportion of patients who had no clinical arthritis at all, and the total ultrasound score served as a non-invasive predictor of the bone damage seen on CT.

The authors also point toward practical implications for screening. High-resolution CT, while highly sensitive, is constrained by cost, specialised equipment, and radiation exposure, making it unsuitable for routine use. Musculoskeletal ultrasound, by contrast, is radiation-free, inexpensive, and widely accessible. Based on their finding that ultrasound scores can predict early structural change, the researchers suggest a stratified approach in which ultrasound serves as a first-line screening tool and CT is reserved for higher-risk patients, such as those with persistent subclinical inflammation or severe skin disease. They stop short of claiming that biological therapy prevents progression, calling instead for longitudinal trials to confirm a definitive protective role. Even with that caution, the study adds to a growing consensus that psoriasis is a systemic condition whose earliest skeletal consequences can be seen, and potentially intercepted, long before joints become symptomatic.

Subject of Research: Subclinical synovitis and periarticular bone changes in psoriasis patients and their association with biological therapy

Article Title: Comparative study of subclinical synovitis and periarticular bone changes in psoriasis patients: impact of biological therapy

Article References: Elshok, H. E., Moghazy, A. A., Balbaa, M. F., & Ibrahim, A. M. (2026). Comparative study of subclinical synovitis and periarticular bone changes in psoriasis patients: impact of biological therapy. Egyptian Rheumatology and Rehabilitation, 53(1), Article 75. https://doi.org/10.1186/s43166-026-00446-5

Image Credits: AI Generated

DOI: 10.1186/s43166-026-00446-5

Keywords: psoriasis, psoriatic arthritis, subclinical synovitis, musculoskeletal ultrasound, high-resolution CT, enthesophytes, bone erosions, biological therapy, PASI score, case-control study, enthesitis, joint damage