Hi, thanks for writing to HCM.
Occurence of sudden, sharp and localised pain in the knee joint suggests Intra articular pathology (some problem in the soft tissues inside the joint).
This could be propably due to Meniscal lesion (shock
absorber inside the joint) or due to crushing of infra patellar fat pad (Hoffa's disease) during knee motion.
Inorder to diagnose these conditions, MRI
scan is mandatory.
So i suggest you to consult an orthosurgeon and follow his advice.
Hope this helps