Acute rotational trauma to the knee: poor agreement between clinical assessment and magnetic resonance imaging findings.

OBJECTIVES

To determine the incidence of anterior cruciate ligament (ACL) injuries in the general population; the pathology associated with a knee sprain verified by magnetic resonance imaging (MRI); and the agreement between clinical findings and MRI.

MATERIAL AND METHODS

Inclusion criterion was an acute rotational trauma to the knee associated with effusion. One hundred and fifty-nine consecutive patients, mean age 27 years and 36% women, were included after clinical assessment at the orthopedic emergency unit. Patients were referred to an MRI examination (1.0 or 1.5 T) performed within a median of 8 days of the initial visit.

RESULTS

The annual incidence of MRI verified ACL injuries was 0.81/1000 inhabitants aged 10-64 years. Fifty-six percent (n=89) of those included had sustained an ACL injury of whom 38% had an associated medial meniscus tear. There was a poor agreement between initial clinical antero-posterior laxity and MRI verified presence of an ACL tear (kappa 0.281). Every second patellar dislocation was diagnosed as a ligament injury.

CONCLUSION

Our findings indicate that the incidence of ACL injuries is higher than previously described. We also show that the first clinical examination after an acute knee trauma has a low diagnostic value. Further assessment with MRI improves the chances of a correct diagnosis of intraarticular pathology and is recommended in the early phase after a rotational knee trauma.