What is the definition of lameness in dogs?

Lameness in dogs is characterized by an irregularity in the dog's gait, which can manifest as limping or difficulty bearing weight on one or more limbs. This abnormality indicates that there is an issue affecting the dog's mobility, often related to pain, discomfort, or an underlying medical condition. By recognizing these gait irregularities, owners and veterinarians can identify potential issues such as injuries, joint diseases, or musculoskeletal problems, making it crucial for accurate diagnosis and treatment.

The other options do not accurately define lameness. A decline in energy levels, for instance, may indicate other health problems but does not specifically pertain to gait irregularities. Similarly, changes in dietary habits or a decrease in playful behavior can be symptoms of various health issues, but they are not direct indicators of lameness.