We retrospectively reviewed the hospital records of 68 patients diagnosed with posterolateral corner (PLC) knee injuries by a specialist knee consultant in two hospitals over the period from 2005 to 2009.

Injuries were diagnosed based on a combination of findings from clinical testing together with results of imaging and arthroscopic findings.

Over 75% of patients presented within 24 hours of their injury with an average presentation at 8 days post-injury. 92% of patients complained subjectively of instability.

We found PLC injuries were most often combined with ACL injury and secondarily with PCL injury and only 12% were isolated lesions of the PLC. The most common mechanism of injury was a non contact twisting injury (52%) confirming the importance of recognising that often no direct contact occurs in PLC injured knees.

The average delay to diagnosis was 30 months from time of injury. Over 70% of the injuries were not identified at the time of initial presentation, with the PLC injury only recognised in those patients who had severe multi-ligament injuries. At the time of referral to the specialist knee clinics only 50% of patients had correctly been given a diagnosis that included injury of the PLC.

Magnetic resonance imaging (MRI) correctly identified 93% of the PLC injuries when performed acutely (within 12 weeks of the initial injury) but only in 27% of patients whose scan was performed over 12 weeks following injury.

We conclude that the diagnosis of PLC injury appears to be frequently missed apart from cases where severe multiple ligament injury has occurred. Clinical history and thorough examination with a high index of suspicion are key in avoiding misdiagnosis of PLC injury.

MRI scans accurately identify PLC injury in the acute phase (within 12 weeks of injury) but may be of limited use following this time period.