Anterior knee pain

Anterior knee pain is common with a variety of causes which can be divided anatomically using a layered approach from superficial to deep:

Superficial soft tissues

• prepatellar bursitis
• Morel-Lavallée lesion
• infrapatellar bursitis 

Extensor mechanism

• quadriceps tendinosis / partial tear
• quadriceps tendon rupture
• patella fracture
• patellar sleeve fractures
• Sinding-Larsen-Johansson disease
• patellar tumors
• patellar tendinosis / partial tear
• patellar tendon rupture
• tibial tuberosity avulsion fracture
• Osgood-Schlatter disease
• patellofemoral instability
• lateral patellar dislocation
• excessive lateral pressure syndrome

Intracapsular extrasynovial

• fat pad impingement syndromes
  • infrapatella fat pad impingement
  • quadriceps fat pad impingement
• para-articular chondroma of the infrapatellar fat pad
• infrapatella fat pad herniation
• cyclops lesion
• ganglion / parameniscal cyst
• iliotibial band friction syndrome

Intra-articular

• plica syndromes
  • mediopatellar plica
  • suprapatellar plica
  • infrapatellar plica (ligamentum mucosum) 
• patellofemoral osteoarthrosis
  • patellofemoral chondromalacia
• inflammatory and depositional arthritis
• lipoma arborescens
• pigmented villonodular synovitis
• focal nodular synovitis
• synovial chondromatosis