Neutering a dog doesn’t stunt their growth. It actually does the opposite. When a dog is neutered before their bones finish developing, they tend to grow taller than they would have if left intact. That’s because sex hormones play a key role in signaling the body to stop growing, and removing those hormones early extends the window of bone growth.
Why Neutered Dogs Grow Taller, Not Shorter
A dog’s long bones grow from soft areas of cartilage near each end called growth plates. As a puppy matures, sex hormones (testosterone in males, estrogen in females) gradually trigger these growth plates to harden and close, which stops the bones from getting any longer. When you remove the source of those hormones through neutering or spaying, the growth plates stay open longer than they normally would. The result is a dog with slightly longer legs and a lankier frame than their intact counterparts.
This is a well-documented effect. Colorado State University notes that early spaying and neutering increases the length of time bones grow, producing a taller pet. The concern isn’t that the dog will be smaller. It’s that the altered proportions may affect how joints align, which can create orthopedic problems down the line.
The Real Risk: Joint Problems, Not Size
When bones grow longer than they were “designed” to relative to the surrounding muscles, tendons, and joint structures, the mechanics of the joint change. This is why early neutering has been linked to higher rates of joint disorders, particularly in larger breeds. A large study across 35 breeds found that neutering before one year of age was associated with two to four times the risk of joint disorders compared to intact dogs in breeds like Golden Retrievers, Labrador Retrievers, and German Shepherds.
The numbers are striking for some breeds. Golden Retriever males neutered before six months had a 25 percent rate of joint disorders. German Shepherd males neutered before six months reached 19 percent. In Rottweiler females spayed before six months, 43 percent developed a joint problem, primarily cranial cruciate ligament (CCL) tears, which is the dog equivalent of an ACL injury. In one small sample of Saint Bernard females spayed before six months, every single dog developed a joint disorder.
These aren’t small differences. And the pattern is consistent: the earlier the neutering relative to the dog’s skeletal maturity, the greater the risk.
Bone Density Stays Mostly Normal
One question that comes up is whether early neutering weakens bones beyond just making them longer. Research using bone density scans on puppies spayed before puberty found no meaningful reduction in bone mineral density or bone mineral content through six months of age. The spayed puppies actually had slightly higher readings, likely because they also weighed a bit more. So the concern with early neutering is really about bone length and joint alignment, not fragile bones.
Timing Depends on Your Dog’s Size
Because larger dogs take longer to reach skeletal maturity, the recommended neutering age varies significantly by body size. Small breeds (under about 45 pounds as adults) finish growing much earlier than giant breeds, so the window where neutering could affect their skeleton is shorter.
Current guidelines based on the available evidence break down roughly like this:
- Dogs under 20 kg (about 44 lbs) as adults: Can generally be neutered from six months of age without increased joint disorder risk.
- Dogs 20 to 40 kg (44 to 88 lbs): Waiting until at least 12 months is recommended to allow more complete skeletal development.
- Dogs over 40 kg (88 lbs and up): Waiting until 24 months may be advisable, since these breeds have the longest growth period and appear most vulnerable to the joint effects of early neutering.
These are general guidelines, not rigid cutoffs. The ideal timing for any individual dog depends on breed-specific data, the dog’s expected adult size, and the practical realities of keeping an intact dog (behavioral issues, risk of unplanned litters, housing situations). For many of the 35 breeds studied, researchers found no increased health risks at any neutering age, which means the decision is straightforward for some dogs and more nuanced for others.
What This Means for Your Dog
If your dog is a small breed, neutering at the traditional six-month mark is unlikely to cause any skeletal issues. Their growth plates are already close to closing at that age. If you have a large or giant breed puppy, the calculus changes. Waiting longer gives those bones time to finish growing at their natural pace, which keeps the joints properly aligned and lowers the risk of problems like hip dysplasia and ligament tears later in life.
The bottom line is counterintuitive: neutering doesn’t make dogs smaller. If anything, it makes them a bit taller and leggier. The trade-off isn’t about size. It’s about whether those longer bones create joint stress, and that depends almost entirely on when the procedure happens relative to your dog’s skeletal maturity.