In Gbaya, the notion of weak knees is emphasized in Psalm 109:24 with gbɛŋɛnyɛŋɛ, an ideophone that usually refers to calming down, being at peace. Here: «my knees died [metaphorically] in weakness (gbɛŋɛnyɛŋɛ).»
Ideophones are a class of sound symbolic words expressing human sensation that are used as literary devices in many African languages. (Source: Philip Noss)