Knee pain causes include:

1. ACL injury (tearing of the anterior cruciate ligament in your knee)
2. Avascular necrosis (osteonecrosis) (The death of bone tissue due to limited blood flow.)
3. Baker cyst
4. Broken leg
5. Collateral ligament injury
6. Dislocation: First aid
7. Gout
8. Iliotibial band syndrome
9. Knee bursitis (inflammation of fluid-filled sacs in the knee joint)
10. Lupus
11. Medial collateral ligament injury
12. Osgood-Schlatter disease
13. Osteoarthritis
14. Osteochondritis dissecans
15. Osteomyelitis
16. Patellar tendinitis
17. Patellofemoral pain syndrome
18. Posterior cruciate ligament injury
19. Pseudogout
20. Referred pain from hip area
21. Septic arthritis
22. Sprains (Stretching or tearing of a tissue band called a ligament, which connects two bones together in a joint.)
23. Tendinitis
24. Torn meniscus