A 27-year-old male patient, an elite footballer, presented with complaints of knee instability (sensation of knee giving away while running). Medical history revealed that the patient sustained a tackle injury (direct kick to the anteromedial proximal tibia with the knee in hyperextension) one week prior to admission.
Physical examination revealed ecchymoses-skin abrasions on the anteromedial proximal tibia and clinical evaluation showed abnormal fibular head motion while the anterior and posterior drawer and Lachman tests were negative for a cruciate ligament tear (Fig.1).An ultrasound examination was performed upon request that demonstrated a hypoechoic area posterolaterally to the fibular head (Fig.2).An MRI examination was carried out subsequently that showed hyperintensity throughout the popliteal musculotendinous junction and a feathery appearance of the popliteus muscle with perifascial fluid collections (Fig.3,4).Additional findings were also a wavy popliteofibular ligament, increased signal in and around the fibular insertion of the lateral collateral ligament, integrity of the cruciate ligaments, tibial bone marrow oedema and increased signal-wavy contour of the anterior tibiofibular ligament (Fig.4,5).Fluid collections were also depicted around the interosseous tibiofibular membrane (Fig.5). The diagnosis of a complex posterolateral corner knee injury was thus established and the athlete was referred to a specialised orthopaedic centre for surgical reconstruction.
The posterolateral corner (PLC) of the knee is a complex area both anatomically and functionally [1-3]. It consists of several structures that are responsible for posterolateral knee stabilisation by resisting and preventing external rotation, varus angulation and posterior translation [1-3]. The PLC is not consistently defined in the orthopaedic-radiologic literature but most anatomic dissections and biomechanical studies include the popliteal tendon, the lateral collateral ligament, the popliteofibular ligament, the posterolateral capsule, the arcuate ligament and the fabellofibular ligament [1-4]. The PLC is also reinforced superficially by the iliotibial tract and the biceps femoris tendon. Variations in PLC anatomy do exist and may complicate image interpretation [1-4]. Injuries of PLC are usually traumatic and most commonly are associated with other ligamentous-meniscal injuries. The fundamental role of PLC as a static and a dynamic knee stabiliser is also attenuated by the fact that reconstruction of cruciate ligaments tears may result in failure if concomitant PLC injuries are not identified and treated [1-5]. Isolated injuries to the PLC without associated cruciate ligament tears, like in our case, occur rarely and represent less than 2% of all knee ligamentous injuries [1-5]. Acquisition of a precise history of the mechanism of trauma is of paramount importance and may aid in the correct diagnosis. Two patterns of force exertion are described that may result in PLC injury: a) a direct mechanism, in which a posterolaterally directed force is applied in the proximal medial tibia, causing knee hyperextension with concomitant varus and external rotation and b) an indirect mechanism which is characterised by a forceful knee hyperextension with concurrent tibial external rotation [1-5].A combination of forces-mechanisms may also contribute in PLC injury as in sports and motor vehicle accidents. Magnetic resonance imaging may demonstrate the entire spectrum of PLC structures and associated injuries that may go undetected on clinical examination [1-5]. What makes our case interesting is the combination of a PLC injury with an associated superior (proximal) tibiofibular joint injury. The anterior tibiofibular ligament is composed of two to three bandles while the posterior tibiofibular ligament is usually a single thick band [6-8]. The interosseous membrane plays also a great part in the tibiofibular syndesmosis. Our patient sustained a direct kick in the anteromedial proximal tibia and the posterolaterally directed force resulted in this uncommon complex PLC injury. Familiarity with the anatomy of this region and a mechanism-based image interpretation algorithm may help correct assessment of such complex knee injuries.
A complex posterolateral corner injury
Based on the patient’s past history of trauma (a front tackle leading to force on the anteromedial aspect of the proximal tibia, causing knee hyperextension combined with valgus and external rotation stress) and the provided MRI images, there is evidence of varying degrees of injury to the posterolateral corner (PLC) structures of the right knee, primarily including:
Considering the patient is 27 years old, a professional soccer player, presenting with a “giving way” sensation in the knee, the mechanism of injury, and the MRI findings described above, the most likely diagnosis is:
If further confirmation via arthroscopy or additional MRI sequences is obtained, the precise degree of ligament tear can be clarified, and surgical indications can be assessed.
Based on the current diagnosis, the following is a general treatment approach and recommended rehabilitation exercises:
When developing a specific exercise prescription, the FITT-VP principle can be applied:
Throughout the rehabilitation process, especially post-surgery if applicable, closely observe whether there is any recurrent instability or risk of re-injury during knee activities. Adhere to recommended timelines for bone healing and ligament reconstruction as indicated by medical guidelines.
Disclaimer:
This report is based on the existing imaging and clinical information for reference only. It does not replace an in-person consultation or individualized treatment plan by a professional physician. If there are any concerns, it is recommended to seek medical attention or consult an orthopedic specialist.
A complex posterolateral corner injury
