Developmental orthopaedic disease and early osteoarthritis of the temporomandibular joint in a 15‐month‐old Quarter Horse filly
Authors: Pimentel K. L., Allen A. L., Carmalt J. L.
Journal: Equine Veterinary Education
Summary
# Editorial Summary A 15-month-old Quarter Horse filly presenting with progressive hard swellings over the left temporomandibular joint (TMJ) since weaning at four months, alongside right metatarsophalangeal joint involvement, prompted radiographic investigation that revealed severe osteoarthrosis with osteochondrosis-like lesions in both TMJs. Post-mortem examination with computed tomography and histopathological analysis confirmed early osteoarthritis associated with osteochondrosis-like changes in the left TMJ and right metatarsophalangeal joint, with additional early OA identified in the right hind proximal interphalangeal joint. The case demonstrates that developmental orthopaedic disease (DOD) can manifest in the temporomandibular joint alongside more typical sites, with clinical signs detectable from four months of age and progressive enlargement through the first year of life. For practitioners managing growing horses—particularly those with predisposing breeds or nutritional imbalances—this case highlights the importance of recognising subtle TMJ abnormalities early, as multifocal DOD involvement carries a poor prognosis for performance and quality of life. The temporomandibular joint should therefore be included in orthopaedic screening protocols for young horses presenting with developmental concerns, particularly when investigating hard swellings in the head region.
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Practical Takeaways
- •TMJ swelling detected at weaning or shortly after should be investigated promptly with imaging, as early osteoarthritis can develop and progress rapidly in young horses
- •Developmental orthopaedic disease may manifest as multi-joint involvement; thorough radiographic screening of multiple joints is warranted when one joint shows osteochondrosis-like lesions
- •Early recognition of progressive TMJ disease is critical for assessing performance prognosis and making management decisions, as severe cases may have poor long-term outcomes
Key Findings
- •A 15-month-old Quarter Horse filly presented with progressive TMJ swelling since weaning at 4 months of age associated with severe osteoarthrosis and osteochondrosis-like lesions
- •Radiographic and CT imaging revealed early osteoarthritis with osteochondrosis-like lesions affecting multiple joints (TMJ, MTPJ, and PIPJ)
- •Histopathological examination confirmed early osteoarthritis in the left TMJ associated with osteochondrosis-like lesions
- •The severe, multi-joint presentation resulted in poor prognosis and euthanasia of the affected animal