Is a displacement of the medial meniscus root a tear? What kind of damage is being done every time the knee clunks?

Something slipping. In the knee there is both a medial meniscus and a lateral meniscus. The meniscus is cartilage and it can tear and it can slip. Slipping can be felt as you suggest but other things can cause a clunk like the patella - the kneecap. Imaging studies can actually show slippage. Does your knee lock. Locking is a common complaint of meniscus tears. To tell if you have damage you need evaluation.
Usually does. Displacements of meniscii usually happen after a tear of its attachments or injury to its substance. In either case it can be symptomatic and needs to investigated as the treatment depends on the findings.

Related Questions

What causes my knee to throb all the time? Could this be caused by a medial meniscus displacement that I have? Please explain

Knee pain. Two most common reasons for knee pain at your age are 1) inflammatory issues such as arthritis/chondromalacia and 2) meniscus tears. If your doctors do not recommend surgery, then you should try pt and/or injections of either cortisone or hyaluronic acid. Read more...