If the kneecap does not track smoothly a patient may develop pain in the front of the knee - so-called 'anterior knee pain' - often on going down stairs or on squatting and often accompanied by alarming crunchy noises. Noises may precede any pain and are a warning symptom.
The pain and noises in the early stages do not necessarily mean the there is joint damage - but that the mal-alignment (i.e. bad alignment) and mal-tracking of the bone over the knee joint on bending and straightening is causing excessive strain on the bones and soft tissues.
The telling symptom is that the pain and noises are related to going down hills or stairs, and that there is no problem with going up hill or up stairs.