Irreducible knee dislocations (IKD) are rare and can often be missed or mis-daignosed. The incidence of knee dislocation is quoted between 0.01% and 0.2% of all orthopaedic injuries, with up to 4% of these dislocations sub-classified as irreducible. The primary aim of this systematic review was to analyse cases of IKD described in the literature, with a secondary aim of producing a streamlined approach for managing these patients.
Patients & Methods: A systematic review of the literature was conducted on 1st September 2021 in accordance with the PRISMA guidelines using the online databases Medline and EMBASE. The review was registered prospectively in the PROSPERO database. Case reports or clinical studies or reporting on IKD were included. The studies were appraised using the Methodological Index for Non-Randomized Studies (MINORS) tool and Newcastle-Ottawa quality assessment scale.
The search strategy identified 60 studies eligible for inclusion, giving a total of 114 cases of IKD. Posterolateral dislocation was most common, seen in 85% of cases. The dimple sign was present in 70%. All cases required surgical intervention to achieve joint reduction. The most commonly involved structure blocking reduction was the medial collateral ligament (MCL) ± medial structures, seen in 52.4%. MCL reconstruction or repair was carried out in 32.3% cases. The overall incidence of neurovascular injury was 9% and the overall complication rate was 14.4%.
Based on the findings of this SR we conclude that:
i) the most common type of IKDs are PL dislocations, and
ii) the MCL, medial retinaculum and capsule and vastus medialis oblique form the most common structures involved in block to reduction and often will require open reduction and repair in acute setting if arthroscopic reduction fails. The most common pattern of injury to ligament is likely to be ACL, PCL, MCL +/- other structures but the MCL will be the most commonly repaired ligament. The dimple sign is often present and is highly pathognomonic of IKD. The incidence of neuro-vascular injury is uncommon.
iii) The most common post-operative complications likely to be encountered is medial skin necrosis and post-operative knee stiffness. Therefore, patients should be mobilised as early as possible with ROM hinge brace.