Knee injuries affect millions of Americans each year. Acute injuries, which commonly occur among athletes or in occupational accidents, include injuries to the ligaments and menisci. Overuse syndromes include patellofemoral pain syndrome, tendonitis, bursitis, and iliotibial band friction syndrome and occur as a result of repetitive soft-tissue trauma. Whether knee pain is acute or gradual in onset, the treatment plan is based on a timely and accurate diagnosis. This article discusses appropriate examination of the knee and common knee injuries and their causes and treatments, as well as a primer on anatomic function.