The popliteal fibular ligament in acute knee trauma: patterns of injury on MR imaging

Objective To describe the patterns of injury associated with injury to the popliteofibular ligament injury. Materials and methods A retrospective review was performed of 180 MRI scans undertaken for acute knee trauma. Scans were excluded if the time of injury was over 4 weeks from the time of the scan, or if there was a history of septic arthritis, inflammatory arthropathy, previous knee surgery, or significant artefact. An agreed criterion for assessing the structures of the posterolateral ligamentous complex was defined and in each scan, the popliteofibular ligament (PFL) was scored as normal or injured. The menisci, ligaments, and tendons of each knee were also assessed. Results The mean age was 25.7 years (range, 9–65 years) and 72.2 % ( n = 130) patients were male. The PFL was injured in 36 cases (20 %). There is a significant association between PFL injury and ACL rupture ( p = 0.0001), ITB injury ( p = 0.0001), PCL injury ( p = 0.0373), in addition to associations with injury to other posterolateral corner structures including the lateral collateral ligament ( p = 0.0001), biceps femoris tendon ( p = 0.0014), and popliteus tendon ( p = 0.0014). Of our series of PFL injuries, nine cases (25 %) were associated with further injuries of posterolateral corner structures and in 27 cases (75 %) the PFL was the only posterolateral corner structure torn. Conclusions PFL injury is not uncommon in acute knee trauma and is associated with significant internal derangement of the knee, especially anterior cruciate ligament rupture, ITB sprain, and injury to other structures within the posterolateral corner.