Although knee dislocations are uncommon injuries with a reported incidence of 0.2–2 % of all orthopedic injuries, the severity of injury presents multiple challenges to treatment [26]. A systematic approach to management of knee dislocations and their sequelae may avoid missed injuries and devastating complications [27]. The initial encounter with a patient with a PCL and lateral-sided injury may occur after a high-impact injury such as motor-vehicle collision, motorcycle collision, motor–pedestrian collision, fall from height or sporting injury, but it may also occur after a low-impact ground level fall, especially in obese patients. By definition, multiligament knee injuries are high-energy injuries, but may occur via high, low, or ultralow velocity mechanisms. If the encounter occurs in the trauma bay or on the playing field, Advanced Trauma Life Support (ATLS) protocol should be followed. As with any initial patient encounter, a thorough history of the accident will yield information as to the mechanism of injury and the velocity of the injury. A large majority of multiple ligament knee injuries stem from knee dislocations that often spontaneously reduce. Because concomitant and potentially devastating neurovascular injuries are common, a high suspicion for a multiple ligament knee injury must always be maintained. It will be important to obtain information from emergency responders, family, and perhaps on-field physicians who may have witnessed the injury and an observation that “the leg was bent the wrong way” [27]. Obvious physical findings of combined sagittal and coronal plane instabilities are diagnostic of polyligamentous injuries.

If a knee dislocation presents unreduced, the first step should be prompt assessment of neurovascular status and immediate reduction, repeat assessment of neurovascular status, and splinting. The common peroneal nerve may be injured in up to 40 % of all knee dislocations; therefore, the neurologic status is a key step in evaluation [28]. Furthermore, the association of arterial injury after knee dislocation with peroneal neuropraxia or permanent peroneal injury can be as high as 62 % [27]. Thus, any nerve palsy warrants a high index of suspicion for vascular injury.

A thorough assessment of vascular status is a vital step in the evaluation of a known knee dislocation or multiple-ligament-injured knee as up to 64 % of patients may have a vascular injury involving either the artery, vein, or both [26]. Although published reports note that serial physical exams (over a 24-h period) and selective arteriography are a safe practice after knee dislocations [29], most authors recommend assessment of ankle–brachial index (ABI) as a diagnostic predictor of vascular injury after knee dislocation [30–32]. Published reports note 95–100 % sensitivity and 97–100 % specificity of ABI in detecting arterial damage in the absence of hard signs (active hemorrhage, expanding hematoma, absent pulse, distal ischemia, or bruit) [30–32]. The senior author (C.J.W.) has previously published an algorithm for diagnosis of vascular injuries in knee dislocations or multiple-ligament-injured knees (Fig. 16.2) [33]. Even after normal ABIs, suspected knee dislocations should be admitted for serial ABIs (every 4–6 h) for 24 h to detect the formation of thrombus resulting from intimal injury or pseudoaneurysm. If the ABI is < 0.9, then either the “gold standard” arteriogram or a computed tomography (CT) angiogram should be obtained to discover the location and extent of vascular injury. Recent evidence demonstrates that CT angiogram may replace arteriogram as the “gold standard” due to availability and lower cost profile [34].

A detailed physical exam will reveal additional objective characteristics of the knee injury. This begins with inspection for effusions, abrasions, ecchymosis, skin dimples, or lacerations. Multiple studies have documented that an acute traumatic knee hemarthrosis often indicates severe structural damage [3, 4, 35–37]. Fanelli found at arthroscopy that PCL injuries occurred in 38–44 % of knees with traumatic hemarthrosis, and of those injuries more than 90 % occurred in the presence of other knee ligament injuries [3, 4]. Following inspection, ROM and ligament stability testing will reveal any limitation to normal motion and uncover suspicions of ligament injury. Ligament stability tests include posterior sag sign, Lachman’s test, posterior drawer test, pivot shift test, reverse pivot shift test, varus recurvatum test, and the dial test [38]. Combined injuries to the PCL and PLC are suggested by a grade III posterior drawer test, increased rotational laxity of the dial test at both 30° and 90° of flexion, positive varus recurvatum test, and a large reverse pivot shift test [8, 38–40].

Radiographs can be very important in the documentation of knee injuries when abnormalities are present, but normal radiographs do not preclude the presence of a severe injury. Findings of capsular avulsions, marginal tibial plateau fractures, large Segond fractures, or proximal fibula fractures may be harbingers of ligamentous injuries [27]. These findings are distinct from typical tibial plateau fractures (which are less commonly associated with neurovascular injuries). Stress radiograph s can be useful to further characterize injuries to the PCL and PLC [40–42]. For chronic injuries, full-length films may uncover limb alignment abnormalities that when corrected may improve sagittal stability [43, 44]. Multiple authors have highlighted the importance of assessing the posterior tibial slope in treating chronic PCL and PLC injuries. Finally, MRI of the injured extremity will confirm suspected ligament damage and provide information regarding additional intraarticular pathology. In addition, MRI can help to indicate the “personality” and energy of the injury, give the surgeon an indication of the location and extent of injured structures (Fig. 16.3).

Postreduction radiographs should demonstrate a concentric reduction. Hinged knee braces locked in extension stabilize the knee with padding placed in the brace to assist with reduction as necessary. After approximately 1 week of immobilization to permit tissues to stabilize, patients begin gentle ROM. Unstable fractures or vascular injuries may warrant external fixation, but otherwise reestablishing ROM of the injured knee should be the goal. In the senior author’s experience, multiligament knee injuries that have undergone extensive immobilization or external fixation not infrequently develop what we term the “FLASCID” knee syndrome (flexion loss with axial, sagittal, and coronal instability after dislocation). This syndrome is characterized by a woody, stiff knee with highly abnormal translation/rotation kinematics at the tibiofemoral articulation. The FLASCID knee is extremely difficult to treat.

There is much debate regarding management of multiple-ligament-injured knees. The Knee Dislocation Study Group reported on many controversies, including nonoperative versus operative treatment, repair versus reconstruction, open versus arthroscopic, early versus late repair, autograft versus allograft, external fixation versus hinged knee bracing, graft fixation, and rehabilitation [45]. Unfortunately, most treatment decisions are based on lower-quality evidence because published high-quality evidence (levels 1 and 2 randomized controlled trials) is scarce. In general, operative treatment is preferred over nonoperative treatment because of improvements in postoperative outcome scores, and reconstruction is preferred over repair [45–48]. Recently, Stannard et al. published a level I randomized controlled trial comparing postoperative treatment of multiple-ligament-injured knees with hinged external fixator versus hinged knee brace [49]. This report noted that reconstructions that were supplemented with a hinged external fixator had fewer ligament reconstruction failures than those supplemented with a hinged knee brace. However, hinged external fixators can be technically demanding to apply and maintain in the hands of surgeons who are unfamiliar with the device. Furthermore, there are often confounding management issues, including medical condition, obesity, concomitant fractures, extensor mechanism disruption, alignment, and social factors that further complicate treatment decisions [50]. Another factor to consider for PCL injuries is its notable healing capacity. In one study, the authors found that more than one third of MRI grade III PCL injuries (complete discontinuity) are clinically stable at the time of repair, and thus the clinical exam of the PCL at the time of surgery should dictate treatment [51].

In general, we advocate an “all-or-none” approach to surgical management of PCL and lateral-sided structures. This recommendation is based on evidence that the PCL and PLC are codominant in controlling posterior translation, external rotation, and varus, so it is ideal to perform concomitant repairs/augmentations/reconstructions so that all repairs are healing in a kinematic environment that is as close to normal as possible. After an acute presentation, the goal is to address injuries in a window from 14 to 21 days after injury. The scheduled delay provides time for an injured capsule to heal, allows the patient to regain knee ROM, and allows for the repair of torn structures before extensive scarring, shortening, and distortion of normal anatomy has taken place. If surgery is not possible within 3 weeks after injury or the patient presents after 3 weeks, it is typical to delay surgery until at least 6 weeks after injury, when the acute inflammatory response has settled, the knee has quieted, and improved ROM has been restored. Prior to delayed reconstruction, a supervised protocol of motion, ice, and compression will help decrease inflammation and “woodiness” of the injured limb. Attempted reconstruction in the maximally inflamed 3–6-week interval after a high-energy injury is often hampered by difficult anatomic dissection secondary to dense fibrotic tissue, protracted ROM recovery, and arthrofibrosis.

Chronic presentation of PCL and PLC injuries can be mired by loss of ROM as a result of extended periods of immobilization. It is crucial to eliminate a bucket-handle meniscus tear, incarcerated cruciate stump, or unreduced tibial eminence fracture as a cause of loss of ROM before instituting a physical therapy program. If a formal course of therapy fails to improve ROM, arthroscopic lysis of adhesions in the suprapatellar pouch, gutters, and the anterior and posterior compartments of the knee as well as manipulation may be required. Delayed reconstructions can be performed to address residual instabilities once the patient has reestablished a more normal knee ROM.

The following instruments/implants can be helpful and should be available:

Of primary importance to the success of any operation is a knowledgeable operating room team that has experience with the planned procedures. The surgeon, of course, should be prepared for the intended surgery but also unexpected complications that may occur. Patients are positioned supine with the popliteal fossa at the flexion break. The bed should be equipped with a lateral leg post and variable-flexion positioner to support the leg at various flexion angles. Fluoroscopy should be positioned on the opposite side of the bed to confirm radiographic landmarks during reconstruction. Generally, the sterile C-arm is placed in a “rainbow” configuration, so it can be slid into or out of the operative field for fluoroscopic viewing during PCL elevation and PCL/PLC tunnel drilling. The proximal thigh should have a tourniquet for safety but should only be inflated in the absence of arterial injury, and then, only for short periods as necessary. The contralateral limb is often prepped to allow comparative exam as well as a source of potential autografts.

The following steps are generally adhered to for PCL and lateral-sided injuries:

The EUA is an integral part in creation of the surgical planning. As discussed above, the PCL has a remarkable healing capacity, thus a PCL and PLC reconstruction should only be undertaken with clear examination evidence of incompetence. PCL and PLC injury is apparent with a positive varus recurvatum test, unstable posterolateral drawer test, positive dial test, and reverse pivot test. The intraoperative exam can assist the surgeon in selecting the most appropriate reconstruction option (Fig. 16.4). In the absence of recurvatum or excessive external rotatory deformity, it is possible to obtain successful results using a modification of Larson’s technique as described by Arciero [52]. However, when gross disruption of the posterolateral capsule and supporting ligamentous structures is present (evidenced by a positive recurvatum-varus test), it is the author’s preference to utilize a modification of the reconstruction technique originally described by LaPrade [53].

Even in the absence of gross sagittal plane instability, it is the author’s preference to reconstruct/augment the PCL if clinical grade II (B) or worse instability is present (when the tibial plateau lies flush with the femoral condyles on draw testing). In cases where varus/valgus instability is appreciated, a careful comparison to the other extremity is useful. In trying to distinguish between acceptable (trace) instability versus physiologically relevant varus, it is often useful to arthroscopically measure the degree to which the lateral compartment opens to varus stress. Opening of greater than 8–10 mm is likely to create undue strain on the PCL reconstruction if the PLC is not addressed. Once the decision to proceed with reconstruction is reached, the lateral side is exposed prior to arthroscopic reconstruction of the central pivot. Dissection is easier prior to imbibition of the tissues with fluid, and the dissected lateral corner allows low-pressure fluid egress, thereby decreasing the risk of compartment syndrome.

The authors advocate augmentation of the PLC even when primary repair is possible, as outcome studies have shown repair with augmentation to be superior to repair alone [48]. In the literature, there are multiple methods of reconstructing the posterolateral corner. Scientific studies have yet to agree on a method of repair that most accurately reconstructs the native ligaments to a state that leads to an optimal clinical result. Good clinical results have been documented with multiple techniques including the Larson technique, anatomic reconstruction described by Arciero, and by anatomic reconstruction described by LaPrade and colleagues [52–54]. Although the merits of each technique can certainly be debated, significant importance should be directed at the effective implementation of a single technique rather than ineffective implementation of multiple techniques.

The severity of injury to the PLC may dictate the best technique for repair (Figs. 16.3 and 16.4). In cases where mild varus and external rotation instability is present in the absence of recurvatum, the authors utilize the Arciero modification of the Larson technique (Fig. 16.5). However, in cases of moderate-to-severe varus and/or external rotation instability, and any time recurvatum is increased, it is preferable to reconstruct the PLC using the technique described by LaPrade [53]. The senior author has modified LaPrade’s technique to employ suspensory fixation in the tibia, and base the FCL femoral tunnel on both isometric and anatomic landmarks (Fig. 16.6). This reconstruction technique theoretically reconstructs key determinants of lateral-sided stability by reconstructing/augmenting the lateral collateral ligament, creates a “static” popliteus limb that also buttresses the posterolateral capsule, and stabilizes the proximal tibiofibular articulation. The use of suspensory fixation allows for a reconstruction using a shorter graft length.