Red flag rules for knee and lower leg differential diagnosis.

Physical therapists can be frequently a patient's initial encounter after a lower extremity injury, as access to physical therapy services have become readily available without a physician's referral. In 2017, over 65% of physical therapy providers are treating via direct access in United States that allow unrestricted access. In addition to direct access, in an age when at least one of four Americans have multiple chronic medical conditions, it is vital to be able to perform a comprehensive examination, which includes a thorough patient history, systems review, and objective test and measures. Physical therapists should identify red flag symptoms and signs indicating possible pathological condition(s). Based on the findings, a clinical decision should be made to either treat the patient, refer the patient to an appropriate healthcare practitioner, or initiate both treatment and referral. If serious pathology is suspected, it is most prudent to refer the patient appropriately to a qualified medical practitioner.