Article summary of:
Low, D. (2025). Cumulative gonadal hormone exposure is nonlinearly associated with risk of canine cranial cruciate ligament disease: a generalised additive model analysis of 20,590 dogs (1988–2023). Journal of Small Animal Practice. https://doi.org/10.1111/jsap.70023
Why This Paper Matters
Cranial cruciate ligament disease (CrCLD) is among the most common causes of hindlimb lameness in dogs (Ness et al., 1996; Witsberger et al., 2008). While veterinarians and trainers have long known that gonadectomy (spaying or neutering) can affect musculoskeletal health, this new study by Low (2025) is the largest dataset re-analysis to date—spanning 20,590 dogs over 36 years—and uses advanced statistical methods to reveal a nonlinear relationship between hormone exposure and risk of CrCLD.
The findings refine our understanding of how the age at which dogs are spayed or neutered influences ligament health, offering trainers, veterinarians, and owners clearer evidence on timing decisions.
Key Findings
- Nonlinear risk pattern:
Dogs with the least gonadal hormone exposure (those spayed/neutered earliest) had the highest risk of developing CrCLD. - Risk declines with age at gonadectomy:
- In females, risk dropped to its lowest point at ~1054 days (2.9 years).
- In males, the minimum risk occurred at ~805 days (2.2 years).
- Clinical definition of “early” gonadectomy:
Based on this analysis, the study preliminarily defines “early” as:- Before 2.9 years in females
- Before 2.2 years in males
in the context of CrCLD risk.
- Breed and comorbidities matter:
Hip dysplasia, elbow dysplasia, and specific large breeds (Mastiff, Newfoundland, Rottweiler) were also significant predictors of higher CrCLD risk.
Why This Matters for Dog Trainers and Owners
- Training and Activity Planning
Trainers often manage dogs through adolescence and into early adulthood, when joint health is critical. Dogs spayed or neutered too early may be at higher risk of ligament injury—something trainers should consider when recommending high-impact activities. - Owner Education
Many owners assume “earlier is better” for gonadectomy. This paper challenges that belief, suggesting that waiting until at least two years of age could reduce the risk of one of the most common orthopedic injuries. - Ethology and Hormonal Influence
Beyond orthopedics, previous studies have linked reduced hormone exposure to changes in fear-aggression and behavior (Starling et al., 2019). Trainers dealing with behavioral concerns may need to consider hormone history as a factor in case assessments. - Population-Level vs. Individual Decisions
While the study offers population-wide trends, it does not prescribe a one-size-fits-all approach. Trainers should support owners in making informed decisions with veterinarians, considering breed predisposition, lifestyle, and health history.
How This Paper Advances Knowledge
Earlier studies often treated gonadectomy as a categorical variable (early vs. late, intact vs. neutered), potentially oversimplifying outcomes. By treating hormone exposure as a continuous variable and applying generalised additive models (GAMs), Low (2025) reveals subtler, nonlinear associations that were previously masked.
This approach mirrors advances in human epidemiology, where cumulative hormone exposure is studied in relation to long-term disease risk (e.g., Cote et al., 2023). For veterinary science, this represents a methodological leap forward and may guide more refined recommendations in the future.
Conclusion
This study strongly suggests that very early gonadectomy increases the risk of cranial cruciate ligament disease and that waiting until after 2–3 years of age (depending on sex) may mitigate this risk.
For trainers and owners, this means:
- Understanding that hormone exposure influences not just reproduction, but musculoskeletal integrity.
- Recognizing that “early spay/neuter” is not a simple cutoff but should be reconsidered in light of this nonlinear data.
- Collaborating with veterinarians to balance orthopedic, behavioral, and population-level concerns when making spay/neuter decisions.
📄 Full paper download below:
Responses