Patellofemoral pain syndrome (PFPS)
Iliotibial band syndrome (ITBS)
Chondromalacia patellae (CMP)
Patellar tendinopathy (or as it is commonly known; patellar tendonitis or patellar tendinitis)
Osgood–Schlatter disease (OSD), also known as apophysitis of the tibial tubercle
Medial collateral ligament injury (sprain or tear to the MCL)
Knee arthritis
Knee osteoarthritis
Tear in ACL and meniscus