Never ignore anterior knee pain!!
Recently I saw many patient with various severities of anterior knee pain, usually it is called patellofemoral pain syndrome by doctors. Some patients just feels knee pain behind the knee cap when walking downstairs and running with a negative MRI finding; some with mild damage to the patellofemoral cartilage, some with no cartilage left so severe function limitations (patellofemoral arthritis).
The treatment of patellofemoral pain syndrome is straightforward, stretching vastus lateralis and strengthening vastus medialis. Combining acupuncture, it usually can be solved in 4 to 5 sessions.