Feeling discomfort, pain on right knee when sitting. already done an arthoscopy and found chondromalacia on the other knee ( left)?

Knee pain etiologies: There are multiple origins for knee pain. If you've already been diagnosed with chrondromalacia patella in one limb, that would be a likely possibility for the other (softening of the cartilage) can signal blood flow changes to the subchondral bone plate under the cartilage and future fibrillation and destruction. You also need to rule out plica syndrome and sciatica. Seek an MRI of the extremity.