A sharp ache beneath the knee after a five kilometre run can be easy to dismiss, especially if walking home was still manageable. The picture may look different the next morning, when stairs hurt and the knee feels less settled. Stopping all activity is not always necessary, but pushing through worsening pain can also prolong the problem.
A sports physiotherapist can assess whether symptoms relate to a rapid increase in training, reduced muscle capacity, joint movement, footwear, technique, or a condition that needs medical review.
Pain signals that something needs attention, but it does not identify the cause by itself. A local sports physio cronulla search can be a starting point, provided the appointment includes a careful assessment rather than a quick label.