Modifiers matching stiffness:

• muscular,

Simple categories matching muscular:

• tissue,
• activity,
• abnormality,
• joint,
• work,
• disorder,
• structure,
• symptom,
• phenomenon,
• organs,
• region,
• control,
• sac,
• effort,
• pathology,
• exertion,
• discomfort,
• artery,
• problem,
• vessel,
• pain,
• area,
• spasm,
• ache,
• dystrophy,
• group,
• action,
• organ,
• dog,
• movement,
• stiffness,
• condition,
• lameness,
• disease,
• part,