Objectives: To characterise the clinical presentation, radiographic findings and treatment of idiopathic carpal hyperextension (ICH) in cats.
Methods: Medical records were reviewed retrospectively for cats diagnosed with ICH between 2018-2025 across multiple institutions. Data collected included signalment, clinical presentation, diagnostic findings, treatment approaches and outcome.
Results: 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 (0-2 years) and another in older cats (9-13 years), with a high proportion of purebreds, notably Shorthair (n=6). All cats presented with carpal hyperextension without history of significant trauma. Eight cats were bilaterally affected (66%), 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 (100%), thoracic limb lameness (66%) and carpal swelling (16%). Cats without lameness had normal weight bearing with an abnormal stance or gait (mechanical lameness). Radiologically, increased angulation at the antebrachiocarpal joint was seen on all stressed radiographs and hyperextension at the metacarpophalangeal and interphalangeal joints in five cats (42%). All cats were initially managed conservatively (mainly rest and NSAIDs), four carpi treated conservatively with long term follow up had a good outcome, the outcome was unknown in the hyperextension persistent in eight carpi. In the other four cats (eight carpi), bilateral pancarpal arthrodesis surgery was performed, single staged in one cat and at separate times in the other three cats following development of carpal hyperextension in the contralateral limb.
Conclusions and clinical relevance: ICH represents a clinical entity in cats characterised by carpal hyperextension without trauma history, frequent bilateral involvement andbreed predisposition for Shorthair cats. There is a potential for delayed contralateral limb involvement, so long-term monitoring is recommended.
