Myotonia Congenita in Labrador Retrievers: When Muscles Won't Relax

Myotonia congenita is a genetic disorder affecting the muscle cell membrane's ability to regulate chloride channels, which are part of what allows a muscle fiber to relax normally after contracting. In an affected dog, muscles remain contracted longer than they should after voluntary movement, producing visible stiffness, a stilted or bunny-hop-like gait, and sometimes an enlarged, firm appearance to affected muscle groups, particularly noticeable in the hind legs and sometimes the face and tongue.

This is fundamentally a muscle and nerve-signaling issue, not a joint, bone, or ligament problem, which is an important distinction because it means the usual orthopedic workup — X-rays, joint palpation — won't show anything abnormal. Diagnosis instead relies on the characteristic clinical presentation plus electromyography (EMG), which can detect the specific abnormal electrical activity in affected muscles, and sometimes genetic testing if a specific mutation has been identified in a dog's lineage.

This is a genuinely rare, hereditary condition, documented in only a small number of individual lines across several breeds including some Labrador lineages, rather than being a widespread breed-level concern the way hip dysplasia or ear infections are. Most Labs will never encounter this condition at all.

The pattern here is genuinely different from typical growth-related awkwardness — here's what to look for specifically.

If you think your Lab has myotonia congenita, the plan is three steps: write down what you have seen and when it started, book a veterinary appointment rather than waiting for the next flare, and take video of the behaviour or symptom before you go — the thing you are worried about rarely happens in the consulting room. Screening in the parents covers hip dysplasia, elbow dysplasia, obesity.

What the vet visit should produce is a diagnosis and a written plan, not just reassurance: what is being ruled out, what the monitoring interval is, and which signs mean you come back sooner. Ask what the treatment costs across a year rather than per visit, because that is the number that decides whether you are managing this condition or reacting to it.

Between appointments, keep a short log — dates, what you saw, what changed. It is the single most useful thing an owner brings to a follow-up, and for myotonia congenita it is often what separates a clear pattern from a guess.