Brief Answer:
Softening of cartilage to down to bone

Detailed Answer:
Hello
Thanks for posting
I have gone through your query and understand your concern.
Chondromalacia is graded on a 1-4 scale. 1 means softening of cartilage, 2 means some frayed edges, 3 is "crabmeat", 4 is down to bone.
Hope this helps.
Take care

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Brief Answer:
Gas bubbles and tendon may produce sound

Detailed Answer:
Hi
It’s good to see you.
If knee popping occurs without any associated pain, it is usually due to either gas bubbles building up inside the joint and bursting, or ligaments/tendons snapping over the joint:
1. Changes in joint pressure can cause tiny bubbles of gas to slowly form in joints. When these gas bubbles burst quickly, they make a popping sound, in a similar way to when you pop bubble-wrap. The technical term for this is cavitation. There is no harm in this and the myth that it makes you prone to arthritis is unfounded.
2. Ligaments and tendons are soft tissues that are positioned around all the joints in our body. Sometimes, when you move a joint (eg. your knee), a ligament or tendon may stretch slightly as it goes over a small bony lump around the joint and then snaps back into place making a popping sound. Again, there is no harm with this knee popping no pain and it doesn’t make you more prone to an injury.

Hope this helps.
Take care

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