Carpal Hyperextension in Nigerian Dwarf Goats

March 31, 2025Goat Journal ContributorHealth, Members Only, Ownership

Carpal hyperextension (CH) is a debilitating orthopedic disease that afflicts many Nigerian Dwarf goats. No scientific literature has yet addressed this disorder, and goat owners have struggled to find effective preventives or treatments. But now, new preliminary research from Oregon State University sheds light on the root causes of CH and opens up the possibility that breeders may be able to eliminate it from the Nigerian Dwarf breed.

What is Carpal Hyperextension?

When a healthy, conformationally sound front leg is viewed from the side, one can draw a straight line from the elbow joint through the knee and fetlock joints. In carpal hyperextension cases, the carpal (knee) joint extends, or bends backward, beyond its normal range of motion. Most affected goats are born normal and develop CH in one or both front legs by around 2 years of age. The condition varies in severity and may worsen over time. Goats with slight hyperextension can live comfortably if given appropriate supportive care; however, goats suffering from severe cases become lame and may experience significant pain and reduced quality of life.

Though injuries can cause CH, Nigerian Dwarf goats are particularly prone to developing CH without any evidence of injury. This has led breeders to hypothesize that carpal hyperextension in Nigerian Dwarf goats results from genetics, improper diet, inadequate mineral supplementation, a problem metabolizing minerals, or a combination of these factors. The fact that CH turns up frequently in some bloodlines and rarely in others suggests that the condition may have a hereditary basis, even if other factors contribute.

Some owners believe that providing free-choice, comprehensive mineral supplementation prevents carpal hyperextension in their goats, but results and opinions regarding the efficacy of this method vary. Once CH manifests, no reliable cure has been found. Improvement is uncommon. Pain and inflammation management is usually the most the goat’s owner can do to help.

New Research on Carpal Hyperextension

In response to the goat community’s entreaties for answers, Dr. Erica McKenzie from the Carlson College of Veterinary Medicine at Oregon State University and Dr. Leah Streb of the UC Davis School of Veterinary Medicine teamed up to research carpal hyperextension. The study was entirely crowdfunded through OSU’s “The Wonky Leg Campaign,” demonstrating goat owners’ desire to get to the bottom of the problem.

Dr. Streb and Dr. McKenzie shared their initial findings in a Zoom presentation entitled “Characterization of Carpal Hyperextension in Nigerian Dwarf Goats.” The study included 36 goats with CH and a healthy control group of 64 related animals from 17 farms. They selected only registered animals for pedigree analysis.

From this pool of goats, the researchers collected a wide array of information — including weight, body condition, medical history, and management/dietary history — to determine which factors were associated with carpal hyperextension.

“Probably the most important part,” Dr. Streb says, was the goniometry (range of motion/joint angle) measurements they took to develop the first clinical description of CH in Nigerians. Healthy goats’ carpal joint angles were 0 degrees (i.e., straight), whereas the joint angles of the affected goats measured -10 degrees or more.

Healthy legs: This Nigerian Dwarf doe, SG Better Wayz Isabelle, received an official linear appraisal score of Excellent in front leg conformation. Note her straight, healthy legs. Photo credit: Kathy Beck-Mullins, A Better Way Farm.

This young doe began exhibiting carpal hyperextension in her right front leg when she was just over a year old. CH can be much more severe than this. Photo credit: Preferred to remain anonymous.

The researchers also collected blood samples for DNA analysis and trace mineral testing. No significant differences were found between the blood trace mineral levels of affected and healthy goats, and the researchers currently see no clear evidence that either diet or minerals play a role in CH. However, this is an area of ongoing study, as it’s difficult to identify trends among the countless variables in different farms’ feeding and management practices.

Interestingly, pedigree analysis revealed that all the affected goats descended from a single buck. However, Dr. McKenzie and Dr. Streb stress that the common ancestry among goats with CH may only reflect the widespread shared ancestry within the breed. All Nigerian Dwarf goats in the U.S. descended from a relatively small population of founding animals, so the researchers need to look at more pedigrees before determining that one buck is solely responsible for CH. Even if he is, many healthy goats may descend from him as well; therefore, the researchers won’t release his name at this time.

Regardless, the preliminary evidence does point to a genetic component. In an interview on the American Association of Small Ruminant Practitioners’ podcast Baas & Bleats, hosted by Dr. Sarah Lowry, Dr. Streb explained that their DNA analysis identified a “region of interest” in which they suspect a gene might be causing the problem. Dr. McKenzie added, “There is supporting evidence … that it does appear it might be heritable, and if there is any chance to isolate that gene and come up with a simple hair or blood test … that would be wonderful.”

The research needed to confirm that CH is genetic is on hold until they receive enough funding. Developing a genetic test would cost around $50,000.

Selectively Breeding to Prevent Carpal Hyperextension

With both experiential and scientific evidence indicating that carpal hyperextension likely has a genetic component, Nigerian Dwarf breeders should consider how to address the issue going forward. Is it worthwhile or even ethical to breed or sell goats with CH? Many breeders believe it is not. To answer that question, we need to understand how offspring inherit the disease from their parents and if preventable secondary factors trigger it. However, as more research emerges and public awareness of CH grows, we expect buyers will gravitate toward breeders who actively select against CH in their herds.

It’s an inconvenient fact of livestock breeding that no animal will ever be perfect, but an ethical breeder’s goal should be to reduce the prevalence of bad traits and perpetuate the healthiest animals possible. Genetic testing has been used to successfully control or eliminate genetic diseases in other animals, and, thankfully, Nigerian Dwarf breeders may soon have that tool available. Until then, they can continue to use selective breeding and good management to minimize occurrences of carpal hyperextension in their herds.

REBECCA KREBS is a freelance writer who breeds registered Nigerian Dwarf goats at Krebs Dairy Goats in the Rocky Mountains of Montana. She enjoys poring over pedigrees and participating in the DHIR milk test program. Find her farm online at www.krebs.farm.

Sources:

Lowry, S. (Host). (2024, May 2). Carpal hyperextension in Nigerian Dwarf goats with Dr.’s Erica McKenzie & Leah Streb (Season 3, Episode 5) [Audio podcast]. In Baas & Bleats. American Association of Small Ruminant Practitioners. https://baasandbleatsaasrp.buzzsprout.com/1986892/episodes/14999620-carpal-hyperextension-in-nigerian-dwarf-goats-with-dr-s-erica-mckenzie-leah-streb
Niemann, D. (Host). (2024, February 28). Carpal Hyperextension in Nigerian Dwarf Goats (Episode 123) [Audio podcast]. In For the Love of Goats. Thrifty Homesteader.
https://thriftyhomesteader.com/carpal-hyperextension-in-goats/ Streb, L., & McKenzie, E. (2023, June 6). Characterization of Carpal Hyperextension in Nigerian Dwarf Goats [Video].

Originally published in the March/April 2025 digital issue of Goat Journal