Sometimes, knee pain is caused by age-related wear and tear that degrades the cartilage. Cartilage is a type of soft tissue that cushions the spaces between the bones within a joint, such as the knee. If it wears away, the bones can rub against each other, causing pain and inflammation that worsen over time.
This is a companion discussion topic for the original article at https://patient.info/features/bones-joints-muscles/knee-pain-that-wont-go-away-when-is-it-time-to-get-a-scan