8.12 Combined ligament injuries around the knee

These injuries include a spectrum of severities ranging from a cruciate ligament rupture plus a minor tear of a collateral ligament to frank dislocation of the tibiofemoral joint (Box 8.12.1). Since most dislocations spontaneously reduce, their incidence is considerably higher than was once thought. Any knee with ruptures of three or more ligaments or a major disruption of two ligaments has likely to have been dislocated at the time of injury. Awareness of this is important because of the risk of neurovascular injury associated with knee dislocation. Although the majority of these major injuries are associated with major trauma, in the morbidly obese, knee dislocation can occur with relatively minor injury.

This is dealt with in detail elsewhere in this book, but some important points need to be made. Firstly, awareness for the potential for a knee dislocation is important. Any knee that has multiple plane laxity may have dislocated, particularly one in which there is not a tense haemarthrosis from leakage of blood into the soft tissues through capsular tears.

Neurovascular injury should be ruled out. The authors’ preference is that all such knees should have an angiogram as Doppler assessment cannot identify intimal flap tears of the artery that may need surgery.

If the knee is dislocated at presentation, it should be reduced immediately. Very rarely it is irreducible if the femoral condyle (usually medial) has protruded through a rent in the soft tissues. The initial management for the knee joint is then to maintain congruent reduction. If the posterior cruciate ligament (PCL) is ruptured, a fixed posterior subluxed contracture can develop. Regular x-rays to ensure maintenance of congruent reduction are important.

Usually an adequate brace will suffice, and allows early joint motion and icing to reduce swelling and avoid early contracture formation. Bridging external fixation should really only be used to protect arterial repairs or reconstructions. In other circumstances, an external fixator interferes with the ability to treat the soft tissues properly, runs the risk of pin tract infections, and frequently holds the joint in a subluxed position.

Magnetic resonance imaging (MRI) helps to establish the anatomy of the injury, but is no substitute for clinical assessment which gives greater detail about the severity of any instability.

There are few justifications for non-surgical management of a knee that has actually dislocated as this tends to lead to an unfortunate combination of stiffness, instability, and rapid deterioration with chondral damage. There is still considerable debate as to whether surgical repair or reconstruction of the injured ligaments should be undertaken within the first 2–3 weeks, or delayed 6–12 weeks following injury. Certain factors may determine the options available. If vascular reconstruction has been undertaken or there has been an open injury, then delayed treatment of the ligaments may well be necessary. Best results from treatment occur when surgery is undertaken around 2 weeks from injury. Any time after this the repair of ruptured soft tissues is often impossible and only reconstructive procedures can be undertaken. Posterolateral corner injuries, in particular, are amenable to repair. The results of successful repair are always superior to reconstruction, presumably due to the restoration of normal anatomy with concomitant proprioception. In addition, where the cruciate ligaments are avulsed from bone, they too can be repaired with possible success. By reconstructing all injured ligaments simultaneously there is less risk of overload of the repair or reconstructions undertaken. The provision of congruent range of motion with stability allows the soft tissue envelope to heal at appropriate tension throughout the range of knee motion and is protective of the chondral tissues. Early mobilization also helps restoration of neuromuscular control of the limb.

These injuries are complex and specialist centres are best to be involved, particularly if early surgery is required.

Careful preoperative assessment is crucial in making the necessary surgical plans. Although most multiligament injuries associated with dislocation require early surgery, a number of injury patterns involving the medial collateral ligament (MCL) and more minor PCL injuries are best treated conservatively at first to allow these structures to heal with bracing. This greatly reduces the amount of surgery that is subsequently required.

Clinical evaluation of the knee includes observation of patterns of bruising and clinical tests of ligament laxity. Plain x-rays including long leg alignment films in chronic cases are essential. MRI scanning is helpful and also highlights significant osteochondral lesions or meniscal pathology.

The management of anterior cruciate ligament (ACL) ruptures is covered elsewhere in this text (see Chapter 8.11). Even with an isolated ACL rupture, the majority of young active patients benefit from reconstructive surgery. In the context of a multiple ligament injury to the knee, however, ACL reconstruction is essential.

The extra-synovial nature of the PCL means that it does have some capacity to heal, particularly if the other ligament injured is the MCL which also has significant healing capacity. Bracing many of the combined PCL/MCL injuries for 6 weeks will restore normal stability and if any subsequent surgery is required it may be much more minor than if undertaken at the very early stage. Nevertheless, if it is clear that clinical assessment shows gross disruption of the PCL then early reconstruction is usually preferable. Clinical examination, which may require an anaesthetic in the acute situation, is best performed by the posterior drawer test. With the foot and therefore tibia in the neutral rotation position and the knee at 90 degrees of flexion, the tibia is pushed posteriorly. If a tibiofemoral ‘step off’ is present but less than the normal side, then this represents Grade 1 laxity. If the tibia is level with the front of the femur (i.e. there is no step off) then this is Grade 2 laxity. If the tibia has sagged behind the distal femur then this represents Grade 3 laxity. If Grade 3 laxity is present then there is virtual certainty of concomitant injury to one or both collateral ligament complexes.

Isolated Grade 1 injuries of the PCL need non-surgical treatment and invariably do well. Grade 3 ligament injuries have a poor prognosis and will require early reconstruction or repair (Figure 8.12.1). This will invariably involve treatment of at least one other ligament disruption. Controversy still reigns regarding the isolated Grade 2 lesions. Patients will often function well with this injury, but there is mounting evidence of significant arthritic damage in the longer term. There is as yet no evidence, however, that early stabilization in this way reduces the long-term risk of arthritis.

The PCL has two functional bundles of fibres, the anterolateral, which is more important, and the posteromedial bundle. Even in cases of complete rupture of both bundles of the PCL, in vitro ‘bench’ testing shows that the addition of a second posteromedial bundle to the reconstruction offers only modest benefit. In the context of acute reconstructions for knee dislocation, most surgeons would only undertake a single-bundle reconstruction. The question remains whether the addition of a posteromedial bundle in the reconstruction is of long-term advantage for more chronic cases.

In the case of a knee with multiligament injury, it is illogical to address all other ligaments apart from the PCL assuming that one will render the knee an isolated PCL-deficient one. Isolated PCL injuries do not involve extensive damage to the capsular structures nor the proprioceptive deficit that occurs with a PCL rupture in the dislocated knee. If one was to reconstruct only one cruciate ligament the PCL should always take precedence. The ACL can always be dealt with at a later stage.

Most MCL injuries of all severities can be treated non-surgically. Those requiring early repair are those in which an MRI scan shows curling up of an avulsed MCL which clearly would not heal well, or cases in which the MCL is ‘flipped’ into the joint or where the meniscus has been extruded with the avulsed ligament. In addition, in cases where both cruciate ligaments are ruptured and require early surgery, failure to undertake early MCL repair is likely to overload the cruciate ligaments’ repairs or reconstructions.

The MCL complex provides the primary restraint to valgus force, which needs to be assessed both in flexion and extension. Opening at all in extension indicates a failure of the posteromedial corner/posterior capsule. In addition, the deep MCL restrains external rotation. A secondary sign of MCL laxity in the presence of ACL laxity, is failure of tibial external rotation to abolish the anterior drawer sign. Knowledge of the anatomy of the medial ligament complex is critical to undertake an effective repair that does not render the knee joint stiff. This anatomy has been described by Warren and Marshall as being in three layers. The most superficial layer 1 can remain intact unless there is major disruption and only once this is incised is the magnitude of the MCL injury visible. The ligament can usually be repaired with suture and suture anchors.

In the chronic setting, most MCL laxity can be dealt with by opening layer 1 and undertaking plication of the loose deep MCL if the laxity is above the meniscus. If braced appropriately this double breasting of the tissue usually leads to good healing. If at arthroscopy it is clear that the laxity is inframeniscal, then layers 2 and 3 may need to be elevated from the tibia before reattachment in an appropriate position. The soft tissue quality may be poor and a simple plicating technique doomed. Although recent focus has been on the posterolateral corner, uncontrolled medial ligament laxity is far more challenging surgically. The superficial MCL and posteromedial corner can be stabilized using a four-strand hamstring tendon or patellar tendon allograft.

The structures involved include the lateral collateral ligament (LCL), the popliteus tendon and associated popliteofibular ligament, biceps tendon and gastrocnemius tendon, and the posterolateral capsule. The primary restraint to varus stress is the LCL. The popliteofibular ligament and attached popliteus tendon form the main restraint to external rotation. Significant injuries to the posterolateral corner are best evaluated by clinical assessment although with improved understanding of the structures comprising this region of the knee, MRI now is increasingly useful.

The LCL is tested by applying varus stress to the knee at 30 degrees but also in extension. Laxity in extension indicates disruption of the posterior structures/capsule. To assess the popliteofibular ligament there are a number of tests. Most knee specialists agree that the ‘Dial test’ is the most reliable. This can be undertaken in the clinic with the patient prone with external rotation of both legs applied simultaneously with the knee at 90 degrees and also, most specifically, at 30 degrees. An isolated posterolateral corner injury will reveal an excess of external rotation most clearly at 30 degrees. If the PCL is involved this increases the sign at 90 degrees. The test is said to be significant if there is more than 10 degrees side-to-side difference in excursion. Also with a PCL rupture, a so-called reverse pivot shift may be present. With the knee flexed and the leg externally rotated to cause posterior subluxation of the lateral tibia, the knee is then extended with concurrent applied valgus to compress the lateral articulation. A ‘clunk’ as the lateral tibial plateau comes forward into reduced position represents a positive result. It is essential to check the opposite knee since around 20% of normal knees have a similar finding. In the chronic case, assessment of gait is essential as significant posterolateral corner injury in the naturally varus aligned limb can lead to a dynamic varus thrust as a patient goes through the stance phase of gait. Particularly bad injuries also have hyperextension present. In these cases, lifting the limb with the great toe will lead to hyperextension, varus and external rotation (a positive Hughston test).

Determining the site of injury to the ligament complex can be helped by MRI scanning and also at arthroscopy where examination of the lateral compartment can show proximal avulsion of the popliteus from direct observation or identify whether opening up occurs above or below the lateral meniscus or indeed both.

Posterolateral corner injuries are best treated acutely since many of the structures can be repaired. This is particularly true in avulsion injuries of the fibular head (Figure 8.12.2). When the biceps, LCL, and popliteofibular ligament all come off as one, or the fibular head is fractured, simple reattachment restores normal laxity to the posterolateral corner. Fibular head fracture fixation is not easy. The common peroneal nerve should be identified and dissected free. The senior author has found that the tension band wiring technique is the most efficient way of fixing the fracture. In other cases in which there are midsubstance ruptures or proximal avulsion-type injuries the structures involved can be repaired directly. At the end of the repair stage of surgery it is essential to check the quality of repair as a reconstruction is usually also required to support the repaired tissues. There are a number of ‘anatomical’ reconstructive procedures described, but unfortunately none of them can provide the dynamic tensioning effect of the popliteus. It may be reasonable therefore to accept non-anatomical compromises such as the modified Larson procedure. This involves taking hamstring tendons from the lateral epicondyle of the femur through a tunnel in the fibular head (Figure 8.12.3). The advantage of this procedure is that it is more peripheral to the centre of the knee at which rotation occurs and therefore its lever arm for effectiveness against external rotation is maximal. If the lateral soft tissues are in reasonable condition then, in chronic cases, a useful option is to detach the lateral epicondyle which is then advanced to retension the posterolateral corner.

Posterolateral corner injuries have a significant rate of common peroneal nerve damage. In a series of 54 cases of posterolateral corner disruption the incidence of injury was 17% and in all but one case this occurred with distal injury to the ligament complex involving avulsion of the biceps’ tendon with or without a fibular head fracture. If a common peroneal nerve injury does occur, then it is essential that an equinus contracture is not allowed to develop and that stretching and splintage are started early.

The main use of osteotomy for multiple ligament injury to the knee is in chronic cases involving a posterolateral corner disruption and natural varus alignment of the limb. In patients who naturally stand in varus, if the soft tissues are simply reconstructed alone then the dynamic stress applied to the reconstruction causes stretching out of the reconstruction or repair over time. In the normal varus knee, this stretching out does not occur since normal proprioception is present through the dynamic contraction of structures such as the biceps, popliteus, and lateral gastrocnemius and the lateral joint is kept closed down under limb loading. Unfortunately, after ligament injury this proprioceptive control is impaired and deliberate realignment of the limb in the coronal plane with osteotomy can be very useful. This is essentially a treatment for LCL laxity, although some authors have suggested that it may enhance restoration of rotational control.

The need for an osteotomy is determined by the presence of dynamic thrust seen on gait or excess varus alignment on long leg x-rays. In osteotomy for osteoarthritis a deliberate deformity is produced to shift the weight-bearing axis to the unaffected compartment of the tibiofemoral joint. When undertaking osteotomy for dynamic laxity for ligament problems, the correction needs to be much less aggressive. The aim is simply to bring the weight-bearing line through the centre of the joint. Calculation of the correct correction is, of course, important. A common error producing overcorrection occurs when there is a failure to recognize that part of the excess varus measured on long leg x-rays may be due to opening of the lateral joint compartment because of LCL laxity. As soon as the weight-bearing line comes across the midline, the lateral compartment will close down as it is loaded, so removing the lateral soft tissue laxity component of the deformity. It should therefore not be included in the calculation of the angle of correction required. A good working rule is that for every excess opening of 1mm, 1 degree of osteotomy correction should be subtracted. The addition of a valgus high tibial osteotomy in the treatment of posterolateral corner insufficiency can be dramatic. It can be undertaken as a preliminary procedure or at the same time as the ligament reconstruction.

The need for distal femoral osteotomy to produce varus in cases of chronic MCL laxity is much less common, but can also be very helpful.

It is easy to think simply in terms of the coronal plane, but the sagittal alignment of the tibial slope is also of great importance in treatment of multiple ligament injury to the knee. The steeper the tibial slope, the greater the tendency there is to anterior tibial translation under knee loading. Equally a flatter than usual or reversed tibial slope will lead to posterior subluxation. Deliberate control of tibial slope at the time of osteotomy can aid ACL or PCL laxity. In cases of ACL deficiency it is preferable to reduce the tibial slope and this is easily accomplished during lateral closing wedge upper tibial osteotomy. Since the approach to the tibia is lateral, the posterolateral corner is easily reconstructed at the same time. If as well as posterolateral corner insufficiency there is PCL deficiency present, then a medial opening wedge osteotomy is preferable. Since this osteotomy is anteromedial, increasing the tibial slope tends to occur when undertaking this procedure.

Realignment of the lower limb with an osteotomy can dramatically improve the quality of results from ligament reconstruction. It is a potent tool in the management of these complex problems.

This is complex and recovery will take place over 2 years following surgery for a knee dislocation. Most of the recovery occurs in the first 6 months, but patients should be counselled about the long process. Soft tissues should be dealt with early on with icing and patellar mobilizations to prevent fat pad contracture. Early motion is also important to reduce stiffness and help protect the joint surfaces. If a PCL reconstruction has been undertaken then flexion should be restricted to 60 degrees in the first few weeks as further flexion increase tension and may stretch the reconstruction. By 6 weeks from surgery, 90 degrees should be achieved in these cases with full flexion allowed by 12 weeks. To help protect the collateral ligaments, restricted extension can be helpful but tends to lead to a fixed flexion deformity which invariably results in a poor outcome. As a result many surgeons now insist on full extension (not hyperextension) as soon as possible after surgery.

Unlike ACL reconstruction, PCL reconstruction has a tendency to stretch and therefore the calf should always be supported when at rest for the first 3 months from surgery. In addition, when undertaking active flexion exercises, the therapist should apply an anterior tibial drawer to protect the PCL. The rehabilitation must progress much more slowly than that for ACL reconstruction.

Weight-bearing status is dependent upon the confidence in the reconstruction, but is generally encouraged as it helps restoration of normal lower limb muscle function.

A strengthening regimen should be started early but must avoid excess stress on the ligament. Proprioceptive drills start early on and become more challenging after 3 months.

With an experienced surgeon the expectation is that at the end of surgical reconstruction in acute or chronic cases, normal laxity of all ligament groups should be obtained (and no more than grade I laxity by end of healing process). The long-term result is usually dependent on the presence or absence of significant chondral damage. In chronic cases, unfortunately most patients will have accumulated some chondral damage from the excess laxity in the ligament complexes, but even in acute cases chondral injury can mitigate against a good result. Although ligament laxity can be restored to near normal, the proprioceptive loss can never be fully addressed. Rehabilitation allows the patient to refine proprioception of the joint by enhanced feedback from structures around the joint. Unfortunately this is never normal and one must never forget what occurs in the situation of a Charcot joint. Some patients who are determined will certainly get back to sport, but particularly where long periods of running are involved, the risk that this will lead to chondral degeneration is high. Most patients are able to undertake activities of daily living and work without difficulty.