What would cause knees to suddenly start acking?

Sudden knee pain can be caused by various factors, including injuries such as ligament strains, tendinitis, or meniscus tears. Additionally, conditions like bursitis or Arthritis can lead to inflammation and discomfort in the joint. Changes in activity levels, improper footwear, or overuse can also contribute to the onset of knee pain. If the pain persists, it's advisable to consult a healthcare professional for an accurate diagnosis and appropriate treatment.