Undiagnosed anterior cruciate ligament rupture. A common problem with poor prognosis

Our knowledge on how often tears of the anterior cruciate ligament (ACL) initially remain undetected and the outcome of the resulting non-operative regimen is still incomplete. To investigate these issues, we conducted a follow-up study in young individuals that 4 to 5 years earlier had sustained a knee injury during a sports event that had been diagnosed as a first-degree sprain.

The patients (n = 54) were grouped according to present symptoms (pain or instability): A, no symptoms (n = 27), B, moderate symptoms (n = 16) and C, severe symptoms (n = 11). Eight group A patients, 11 group B patients and 8 group C patients participated in the follow-up study. Symptoms and level of activity were evaluated and clinical examination of the knee and KT-1000 instrumented measurement of anterior knee laxity were performed.

Increased anterior laxity was demonstrated in 7 patients (1 in group B and 6 in group C). In the same period these injuries occurred, acute ACL rupture was diagnosed in our region in 16 patients. The proportion of overlooked ACL ruptures to injuries interpreted as a first-degree sprain and to total number of ACL ruptures sustained during the same period was at least 7 out of 54 (13%) and at least 7 out of 23 (30%), respectively. The subjective symptom score was higher and Lysholm's and Tegner's scores lower in the patients with increased anterior laxity compared to the patients with no increased anterior laxity. We conclude that ACL rupture may be overlooked in a rather high proportion and that the 4-5 years' result in such injuries is poorer than in those without increased anterior laxity.