Spay and Neuter


Like any surgery, spay or neuter carries certain risks. When you surgically remove a dog’s reproductive organs, you also remove the sex hormones they produce. The sex hormones don’t just affect sexual behaviors …they also regulate your dog’s growth.

Breeders can easily spot the difference between an intact dog and a neutered dog. Neutered dogs have longer limbs, narrower heads and bodies, and they’re lighter in bone.

But spay/neuter doesn’t just change the look of your dog. Here are som facts you need to be aware of …


Dogs’ long bones have a a band of cartilage near the joint called a growth (or epiphyseal) plate. As the growth plate builds bone, the bones become longer.  Once the dog matures, this growth plate turns into bone and the puppy reaches his full height.

1991 research at the University of Florida showed that sterilizing dogs before maturity may delay the closure of some growth plates. This is especially true when only some of his growth plates are closed.


The dog’s elbow and stifle (knee) joints have one bone above and two bones below the joint … so one bone sits on top of two.

If one of those two lower bones stops growing before the other one, they can be different lengths. This means weight isn’t evenly distributed, and there’s increased load on the lower part of the elbow or knee joint.

Chris Zinc DVM PhD DACVP explains …

… if the femur has achieved its genetically determined normal length at eight months when a dog gets spayed or neutered, but the tibia, which normally stops growing at 12 to 14 months of age continues to grow, then an abnormal angle may develop at the stifle. In addition, with the extra growth, the lower leg below the stifle likely becomes heavier (because it is longer), and may cause increased stresses on the cranial cruciate ligament.

In 1993, researchers at UC Davis found that spayed and neutered dogs were twice as likely to suffer cranial cruciate ligament (CCL) rupture.

Other researchers have found sterilization can cause obesity and reduced bone mass, especially in females, which also increases the risk of CCL tears. And spayed or neutered dogs are more than three times more likely to suffer from patellar luxation.


There’s a lot of research into hip dysplasia because it’s so common in large breeds.

Studies show that dogs sterilized before six months have a 70% increased risk of developing hip dysplasia. Van Hagen et al found that dogs neutered six months before hip dysplasia diagnosis were nearly twice as likely to develop hip dysplasia.


Although not technically a joint issue, osteosarcoma is a cancer of the bone … and spayed and neutered dogs are twice as likely to develop this deadly disease.

One study showed that male Rottweilers were nearly four times more likely to develop osteosarcoma than intact dogs. The researchers concluded that the longer the dogs were exposed to sex hormones, the lower their risk of osteosarcoma.


There are other related risks with spay/neuter, including …

• Increased risk of many cancers

• Hypothyroidism

• Diabetes

• Urogenital disorders

• Cognitive impairment

• Obesity

• Surgery or anesthesia complications

Sex hormones play a synergistic role in your dog’s growth and development. Removing them will create imbalance in the body.

Growth plates close at different times depending on your dog and breed. In general, the larger the dog, the later the growth plates will close. In giant breeds, this could be nearly two years old