Elbow is related to Knee. Knee is related to Bend. Bend is part of Road. Road is related to Similar. 
Bridge is part of Guitar. Bridge is related to Troubled. Troubled is related to Concerned. 
Elbow <--RelatedTo--> Knee <--RelatedTo--> Bend --PartOf--> Road <--RelatedTo--> Similar 
Guitar <--PartOf-- Bridge <--RelatedTo--> Troubled <--RelatedTo--> Concerned 