Alpine skiing is an increasingly popular recreational sport worldwide. While the overall injury rate has declined and the pattern of injury changed over the years, the incidence of knee injuries has not changed substantially and accounts for 20 to 30% of all alpine skiing injuries. Medial collateral ligament (MCL) injuries are the most common in skiing, accounting for 15 to 20% of all skiing injuries and 60% of knee injuries in skiers. Tears are commonly isolated, but may occur in association with other ligamentous injuries. Associated meniscal pathology is rare. Isolated MCL injuries are treated nonoperatively with a programme of initial immobilisation, early range-of-motion, and isometric quadriceps strengthening exercises. When full range of motion is achieved, a programme of progressive resistance exercises, isokinetic and closed chain exercises, and functional rehabilitation is instituted. Good results with return to skiing can be expected in most cases. Isolated lateral collateral ligament (LCL) injuries are rare in skiers. There is usually associated cruciate or arcuate ligament complex. Careful physical examination is essential to rule out associated ligament injuries and more complex instability patterns. In the rare case of isolated LCL injury, a similar approach to isolated MCL injury should be instituted. Anterior cruciate ligament (ACL) injuries have become increasingly common in skiers. This may reflect a true increase in the incidence or an improved awareness and ability to diagnose ACL injury. Physical examination and arthrometric analysis are important in assessing the integrity of the ACL. Radiographic and magnetic resonance imaging (MRI) evaluation may be helpful in assessing associated meniscal pathology. Treatment of the ACL-deficient knee is usually surgical. However, prior to reconstruction, a programme aimed at reducing effusion and regaining a full, pain-free range of motion is recommended. Surgical reconstruction is usually with the central third of the patella tendon using a bone-tendon-bone autograft. Postoperative rehabilitation employs a functional staged approach, requiring vigilant supervision by the surgeon. Isolated posterior cruciate ligament (PCL) injury is rare in skiing, constituting less than 1% of all knee injuries in most series. Careful physical examination must be employed to rule out associated arcuate ligament complex injury and more complex patterns of instability. Most isolated PCL injuries are treated nonoperatively with a programme of initial immobilisation in extension, ice, protected weight-bearing, early range-of-motion exercises and progressive isometric strengthening.(ABSTRACT TRUNCATED AT 400 WORDS)