Idiopathic carpal hyperextension in 12 cats (2018-2025)

Case series summaryThe aim of the present study was to characterise the clinical presentation, radiographic findings and treatment of idiopathic carpal hyperextension (ICH) in cats. Medical records from six referral centres were retrospectively reviewed to identify cats diagnosed with ICH between 2018 and 2025. Data collected included signalment, clinical presentation, diagnostic findings, treatment approaches and outcome. The study population comprised 12 cats aged 4 months to 12 years 10 months (median 4 years 3 months) with 20 affected carpi. The age distribution showed two peaks: one in younger cats (aged 0-2 years) and another in older cats (aged 9-13 years), with a high proportion of purebreds, notably shorthairs (6/12, 50%). All cats presented with carpal hyperextension without history of significant trauma. Eight cats (66%) were bilaterally affected, one cat initially presented with bilateral disease, while seven developed contralateral involvement 2-36 months after initial presentation. Common clinical findings included a palmigrade stance (12/12, 100%), reduced weightbearing (8/12, 66%) and carpal swelling (2/12, 16%). Increased angulation of the antebrachiocarpal joint was seen on all stressed radiographs, and mild to moderate periarticular soft tissue thickening was seen in most cases (7/11, 63%). All cats were initially managed conservatively (rest and analgesia, mainly meloxicam); four carpi treated conservatively showed an improvement of hyperextension and weightbearing; the outcome was unknown in the remainder of the carpi treated conservatively. In four cats (eight carpi), bilateral pancarpal arthrodesis (PCA) surgery was performed: a single session in one cat and staged sessions in the other three cats. Major complications occurred in two cats, with one requiring revision surgery. All carpi treated with PCA achieved good long-term outcomes.Relevance and novel informationICH represents a clinical entity in cats characterised by carpal hyperextension without a history of trauma, frequent bilateral involvement, breed predisposition for shorthair cats and a biphasic age presentation. There is a potential for delayed contralateral limb involvement and a variable response to treatment; therefore, long-term monitoring is recommended.