Achondroplasia isn’t something newly developed. It has probably been around for thousands of years and occured due to an early gene mutation in the evolution of the domestic dog.
Glen of Imaal Terriers are, by design, achrondroplastic. This means they are a dwarf breed so have shorter legs and a bigger body. This does cause the front legs to bend around the chest and the feet to turn out but it should not be in an excessive way. Feet placed around the 10 to 2 - 5 to 1 position are ideal whilst ¼ to 3 would be rather excessive and probably cause problems in later life due to the pressure on the “ankle” joints.
The longer body of a Glen doesn’t seem to cause any back problems (disc or spine) but this bigger body with the short legs does mean that growth plate problems are sometimes experienced. The weight of the dog on the ankle, elbow or shoulder joints can cause lameness if sudden shocks are experienced. Normal walking on a lead should be no problem at all to a young Glen of Imaal Terrier but jumping, running up and downstairs or a bit too much rough-housing may find a Glen under, say, fifteen months inexplicably limping. Usually rest is sufficient but if there are any doubts do make an appointment at the vet