Rapidly progressing medical technology sometimes obscures the importance of history and physical examination. This study was designed to assess the value of MRI and clinical examination in the diagnosis of ligamentous and meniscal knee injuries in comparison with arthroscopic findings. In the year 2003-2004, we conducted a prospective, single blind study to assess ligamentous and meniscal injuries of the knee in patients with acute knee trauma. The mean age was 27.9 years. The sex distribution was 81.4% male and 18.6% female; 42.9% of injuries affected the right knee and 57.1% the left knee. All the included patients were ordered a MRI, executed in five separate centres. All patients underwent arthroscopy by the author. Arthroscopic findings were the diagnostic reference. Clinical examination was accurate in 91.4%, and MRI in 88.5% of anterior cruciate ligament injuries. For posterior cruciate ligament injuries, clinical accuracy was 100% and MRI 94.6%. Clinical examination was accurate in 96.9% and MRI in 85.9% of medial meniscal injuries. For lateral meniscus injuries, clinical accuracy was 85.4% and MRI 73.8%. MRI findings showed the lowest correlation with arthroscopic findings in lateral meniscus injuries (r = 0/47). Clinical diagnostic performance was poorest in case of combined cruciate ligament and meniscal injuries. We found an excellent correlation between MRI and clinical findings. However, when MRI is normal, high clinical suspicion and a skilled clinical examination are more reliable.