Medial-Side Injury of the Knee P

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Introduction

Whereas in lateral-side injuries of the knee, clear distinctions have been made between the lateral and posterolateral structures as separate entities, both of which are important in controlling varus laxity and external rotation, medial-sided knee injuries have often been identified with injuries to the superficial medial collateral ligament (MCL). In actual fact, the internal aspect of the knee is a far more complex structure, and the posteromedial corner, with its static and dynamic stabilisers, plays a fundamental role in medial knee stability, in controlling rotation, in the stabilisation of the medi- al meniscus, and in controlling anterior stability when the anterior cruciate ligament (ACL) is insufficient.

Anatomy

The anatomy of the medial aspect of the knee has been adequately described in the literature [1–3]. It extends from the medial edge of the patella to the medial edge of the posterior cruciate ligament (PCL). It can be divided into anatomical areas [2] or layers [1] whereas on a functional level, it is composed of static capsular and non-capsular ligaments and dynamic stabilisers, con- stituted by the semimembranosus tendon with its relative expansions.

According to Sims and Jacobson [4], in the past, the contribution of the

dynamic stabilisers and the effects of injury to the same have been underes-

timated, as most studies are performed on cadavers. Warren and Marshall

divided the internal aspect of the knee into 3 layers according to cadaveric

dissection [1]. The most superficial layer is constituted by the sartorius and

its fascia. The pes anserinus tendons are located between the first and second

layer. The second layer is constituted by the fibres of the anterior retinaculum,

which blends with the first layer to the front, inserting the anteromedial tib-

ial periosteum by the superficial MCL and to the posterior by the semimem-

branosus tendon. The superficial MCL extends from the medial femoral epi- condyle and inserts the proximal tibia 8–10 cm below the articular margin and, deep down, the pes anserinus tendons. The thicker anterior fibres are arranged in a parallel manner whereas the posterior ones are oblique and blend with the posterior capsule of the posteromedial corner of the knee that forms the third layer. This third, deeper layer is constituted by the articular capsule, which is slender to the front and grows thicker centrally and to the rear. Centrally, the articular capsule is reinforced by the deep MCL composed of the meniscofemoral and meniscotibial ligaments. The posteromedial cap- sule blends with the posterior oblique fibres of the superficial MCL and is reinforced by the insertions of the semimembranosus tendon and the poste- rior oblique ligament (PCL). The PCL continues to the posterior and oblique- ly and inserts the adductor tubercle. It is constituted by the upper, middle, and lower bands [5]. The upper most proximal band is attached to the poste- rior capsule and connects below and behind in the expansion of the semi- membranosus. From the adductor tubercle, the middle band inserts the meniscus posterior to the deep MCL and the proximal tibia, just above the direct arm of the semimembranosus. The lower band inserts distally on the semimembranosus and the tibia. It is intimately connected to the meniscus and the posterior capsular, and together with the expansions of the semi- membranosus tendon, they constitute the posteromedial corner of the knee.

This particular anatomical structure was described by Hughston et al. [2] and later by Müller et al. [3] as a static and dynamic stabiliser during coupled motion of the knee, restricting anteromedial rotation (Fig. 1). Five semi-

Fig. 1.Medial side’s ligament of the knee and semimembranosus tendon. 1, Posterior oblique ligament; 2, deep fascicle of medial ligament; 3, superficial fascicle of cut medi- al ligament; 4, semimembranosus tendon

membranosus expansions have been described [1]. The broadest expansion is the direct arm that inserts on the posteromedial corner of the tibia. The pars reflexa passes in depth to the superficial MCL on the medial edge of the tibia.

The third superomedial expansion inserts at the PCL, the posterior capsule, and the medial meniscus, reinforcing them. The fourth insertion is the popliteal oblique ligament and extends laterally to reinforce the posterior capsule, whilst the fifth expansion continues distally and to the rear, blending with the popliteal fascia (Fig. 2).

Functional Anatomy

Müller et al. [3] and Warren and Marshall [6] stated that the anterior fibres of the superficial MCL are tight during flexion and lax during extension whereas the posterior fibres exhibit an opposite behaviour. These concepts were con- firmed by Gardiner et al. [7] in their studies with sensors positioned on the structures of the medial aspect. The deep MCL is tight during flexion and lax during extension. The posterior capsule and the PCL are tight during exten- sion and lax during flexion; however, their function as dynamic stabilisers cannot be evaluated during usual investigations on cadavers [4]. It has been suggested that thanks to the insertions on the PCL, on the posterior horn of the inner meniscus and on the posterior capsule, the semimembranosus tight- ens structures that should be lax when the knee is flexed and contributes to

Fig. 2. Semimembranosus tendon and expansions

meniscus retraction during the flexion of the knee, thus preventing impinge- ment between the femur and the tibia [3, 8, 9]. In their papers, Hughston et al.

[2, 9, 10] emphasised the role of the PCL as the main medial stabiliser against valgus stress and introduced the concept of anteromedial rotational instabili- ty (AMRI), intended as an abnormal excess opening of the medial joint space at 30° of knee flexion, with an anterior dislocation of the medial tibial plateau in relation to the medial femoral condyle. The concept of the PCL as a dynam- ic stabiliser through the expansions of the semimembranosus was taken up by Müller et al. [3], who wrote: “despite its closed topographic relation to the medial collateral ligament, the posteromedial corner is fundamentally differ- ent in nature and function from the tibial collateral ligament”. Warren and Marshall [1], in contrast with Hughston et al. and Müller et al., described the superficial MCL as the main medial stabiliser to valgus stress; however, in their study, they did not find the PCL as a separate anatomical entity.

In studies on cadavers, the section of the superficial MCL causes between 2° and 5° of medial laxity at 30° of knee flexion. The total amount of valgus laxity is limited. The cutting of the PCL and the posteromedial capsule increases medial laxity from 7° to 10° [6, 11–14]. There is agreement in stat- ing that the rupture of the superficial MCL causes laxity during flexion and association with the PCL and the posteromedial capsule in extension. In addi- tion, the cutting of the superficial MCL causes an increase in external rotation [6, 12, 14–17], which is 4–10° greater when the knee is flexed whereas it does not affect internal rotation.

The cutting of the posterior capsule and the PCL causes a 5–10° increase in extra-rotation. Internal rotation also increases considerably after addition- ally cutting the posteromedial complex [12, 14]. The fibres of the PCL are par- allel at the PCL and resist posterior translation and internal rotation.

Through their insertion on the posterior horn of the inner meniscus, the PCL and the posterior capsule act as secondary stabilisers to the anterior transla- tion of the knee when the ACL is injured [3, 8, 18]. The deep MCL does not appear to play an important role in stability in valgus tests but, rather, acts as a medial meniscus stabiliser through the meniscotibial ligament. In the event of a tear of the meniscotibial ligament, there is an increase in the stress on the other knee structures, which resist anterior and anteromedial dislocation, with risks of condyle and inner meniscus damage [19]. In conclusion, one may state that:

- Rupture of the superficial MCL causes a valgus laxity of 2–5° when the knee is flexed and an increase in external rotation when the knee is flexed at 4–10°. The knee is stable in extension.

- Rupture of the deep MCL does not cause an increase in medial instability;

however, rupture of the meniscotibial ligament increases mobility of the

medial meniscus.

- Rupture of the PCL and the posteromedial capsule occurs in association with superficial MCL injury and causes a 7–8° increase in valgus laxity.

Laxity is also present in extension. External rotation with the knee flexed increases by 10–20°, and internal rotation also increases. The meniscotib- ial fibres contribute to the stability of the medial meniscus.

Injury Mechanism

Medial-sided knee injuries are usually caused by an injury of the lower thigh or on the side of the upper leg. They can also be caused by distortion injuries in external rotation. These distortion injuries usually cause injury to the PCL and the posterior fibres of the MCL and may cause a partial or total tear of the ACL. When the valgus injury is associated with external rotation, simulta- neous rotation of the MCL, PCL, and ACL is almost certain [20].

Diagnosis

Clinical inspection is important in identifying the site of tumefaction. The presence of medial tumefaction suggests pathology of the medial aspect and must be differentiated from a haemarthrosis, an indication of ACL tearing.

The site of tumefaction and pain, especially when pressed with the fingertips, indicates the site of the injury. The valgus test at 30° of flexion remains the most important test for evaluating medial knee damage. As with all clinical tests performed on the knee, it must be compared with the healthy side. It must be performed with the patient relaxed and the muscles not contracted.

Extension of the hip helps to keep the ischiocrural muscles relaxed. The thigh rests on the bed, and the knee is flexed by 30°, allowing the leg to hang from the edge of the bed, supporting the limb with a hand whilst the other hand grips the foot and the ankle. In order to better appreciate rotatory instability, which consists in the simultaneous valgus stress opening of the knee associ- ated with the anterior dislocation of the medial tibial plateau in relation to the medial femoral condyle, Sims and Jacobson suggest supporting the sole of the foot rather than the ankle [4].

The positive outcome of the anterior drawer test in external rotation is

another index of rotatory instability. This test is positive when the medial tib-

ial plateau dislocates anterior to the medial condyle whereas the external

aspect of the knee remains stable [10, 21]. According to certain Authors, it is

important to evaluate the presence and absence of a rigid stop during the exe-

cution of valgus stress tests. However, opinions differ regarding the interpre-

tation of this test, as according to Indelicato [20], the absence of a rigid stop

indicates a simultaneous tear of the ACL whereas other Authors indicate the

rupture of the superficial MCL and the PCL. The valgus test must then be repeated with the leg extended. Positive valgus stress tests with the leg extended are an index of a rupture of the superficial MCL and the PCL. A combined tear of the ACL and the PCL must be suspected. As regards the clas- sification of medial stability, as Ballmer and Jakob observed, there is no stan- dardised method or evaluation uniformity [22].

Many Authors divide medial injuries into 3 grades: grade I (first-grade sprain with minimal disruption of fibres, tenderness, solid end point), 0 to 5- mm laxity; grade II (second-grade sprain with more fibre disruption, firm endpoint), 5 to 10-mm laxity in flexion; grade III (complete rupture, no end- point), >10-mm opening of the joint in flexion and extension [23–25]. From this imprecise classification, it is not clear which ligaments are ruptured. The classification method put forward by Hughston et al. [10] also entails a dis- tinction between 3 grades; however, it is more precise in quantifying laxity and the ligaments concerned:

- Grade I: rupture of few fibres, localised pain, and no instability;

- Grade II: rupture of more fibres, pain is more widespread; however, there is no valgus instability;

- Grade III: complete rupture of the ligament with valgus instability. This instability is in turn broken down according to the medial opening: 1+ (<5 mm, IIIA), 2+ (6–10 mm, IIIB), and 3+ (>10 mm, IIIC). A 1+ laxity indi- cates complete rupture of the superficial MCL, and the extension test is negative. A 2+ or 3+ laxity in flexion indicates rupture of the superficial MCL, the PCL, and the posteromedial capsule. Medial laxity is also present in extension.

Treatment

Treatment of isolated medial-sided knee injuries has changed over the past 20

years. Whereas conservative treatment in grades I, II, and IIIA and B injuries

is universally accepted, there is disagreement on whether conservative or sur-

gical treatment is best suited to severe grade IIIC injuries, especially in world-

class athletes, although most Authors favour the conservative treatment

option. Grade IIIA and B injuries of the MCL are treated using an orthosis in

extension and the use of crutches to relieve pain. As soon as pain permits, the

patient starts a rehabilitation programme for joint recovery and isotonic, iso-

metric and, when possible, isokinetic exercises. Load is encouraged with the

orthosis, and crutches are gradually eliminated. Various rehabilitation proto-

cols can be followed for this type of lesion [26]. The resumption of sports

activities depends on the type of sport and the gravity of the injury. On aver-

age, grades I and II injuries require 10 days and grade III injuries 3–6 weeks.

However, in the sports at greatest risk, such as football, the period of inactiv- ity could be longer [26]. In those patients who experience persistent pain caused by lesions to the femoral insertion of the MCL, immobilisation must be maintained until the disappearance of symptoms [20]. If pain and tume- faction appear during rehabilitation, a fracture of the meniscus or cartilage damage must be suspected. The persistence of pain at the articular margin beyond 3 weeks also suggests meniscal injury.

According to many Authors, isolated injuries with valgus laxity of 2+ heal well with conservative therapy although some patients heal with slight resid- ual laxity [27–34]. Isolated grade IIIC lesions will also heal with functional conservative treatment [22, 31, 32, 34–36]. Fetto et al. [27] and Sandberg et al.

[37] found no improvement after operative treatment of isolated grade III lesions. Conservative treatment has also been used on world-class athletes with excellent results [32]. Reider et al. [36] reported outstanding results in 35 athletes monitored for approximately 5 years; 19 patients resumed sports practice within 8 weeks, of whom 16 resumed sports practice within 4 weeks.

The treatment proposed for grade IIIC injuries of the medial aspect [20] con- sists of a knee brace in extension for 2 weeks, however, commencing articular recovery without limitations compatible to pain, load with crutches just bear- able, and without crutches when the patient has achieved a noticeable limp.

The knee brace is gradually removed after 3–4 weeks. Training can be resumed when the limb has regained 80% of its strength in isokinetic tests. In one series, Kannus [33, 38] observed a higher percentage of arthritic degen- eration following conservative treatment of severe medial laxity in grade IIIC injuries.

The criticism of systematic conservative treatment of even isolated medi- al-side knee injuries lies in the fact that such series often do not specify the severity of medial instability [39]. Hughston holds that when talking of grade III lesions, the severity of grade IIIC injuries must be specified and claims that they must be treated surgically. Sims and Jacobson [4] emphasise the concept of AMRI, presented previously by Hughston, as an index of complex rupture of the medial and posteromedial structures of the knee, which requires surgical treatment even in the case of isolated injuries. PCL repair and, when necessary, repair of the semimembranosus tendon and menis- cotibial ligament insertion is of fundamental importance to countering anteromedial rotatory instability. Furthermore, in the event of meniscotibial ligament rupture, the tibia slides forwards, and the stabilising action of the meniscus is therefore lacking and the articular cartilage and the meniscus risks further damage and at higher stress level, as do the other joint struc- tures that resist anterior and anteromedial dislocation of the knee.

In conclusion, many authors believe that acute isolated grade IIIB and C

injuries can be treated conservatively, thus saving surgery for acute-phase

bony ligament avulsions. Others believe that medial injury repair is more suitable, even in isolated injuries where medial laxity is higher than 10 mm with anteromedial rotatory instability. Chronic instability of the MCL/poste- rior MCL is a relatively rare operation indication [40]. Shahane et al. [41]

reported favourable results after an “isometric” proximal advancement and recession of the MCL. Kim et al. [42] and Borden et al. [43] reported anatom- ic-like reconstructions with semitendinosus tenodesis for repair of the super- ficial MCL and PCL, but results were not available. A strip of semitendinosus tendon can also be used to support the PCL [3] (Fig. 3).

Surgical Technique

Surgical technique for medial-side knee injury repair is broken down into four stages:

1. Repairing the meniscus and the posteromedial capsule, fastening it to the tibia

2. Repairing the superficial MCL (tight in flexion)

3. Repairing the PCL and the posteromedial capsule (tight in extension) 4. Repairing the semimembranosus and the capsular extensions thereof.

Firstly, an arthroscopy is performed to exclude intra-articular injury. This examination makes it possible to assess two indirect signs of posteromedial corner injury: meniscal rise during adduction stress at 30° of flexion (Fig. 4)

Fig. 3.Strip of semitendinosus tendon used to support the posterior oblique ligament (POL) and the superficial medial collateral ligament (SMCL)

and injury-site bleeding. Surgical technique involves a curved incision 5 cm above the epicondyle directed distally towards the medial margin of the patel- la. Once the fascia has been exposed, it is cut from proximal to distal anterior to the epicondyle and posterior to the medial vastus muscle fibres as far as the insertion of the pes anserinus tendons. This allows the observance of the pes anserinus tendons distally and the posteromedial corner. The superficial MCL that inserts the medial epicondyle is identified. The deep MCL inserts slightly distally, and the PCL and posteromedial capsule insert at the adduc- tor tubercle. It is also necessary to identify the distal insertion of the superfi- cial MCL situated beneath the pes anserinus tendon (Fig. 5) and the semi- membranosus tendon, with its expansions. The gastrocnemius insertion is freed from the posteromedial capsule using a Homan retractor to protect the vasculo-nervous structures. A retro-LLI arthrotomy is performed through an oblique incision and the posteromedial capsule and semimembranosus ten- don are examined and repaired using bone anchors (Figs. 6, 7), and any meniscal disinsertion is sutured to the capsule. If damaged, the meniscotibial ligament is now repositioned using bones-anchors. A valgus stress test at 30°

allows a clearer indication of the superficial MCL rupture site. Bony avulsions

are fastened using washers and screws, and ligament avulsions are repaired

using bone anchors or screws with toothed washers. The superficial MCL is

repaired with the knee flexed. The posteromedial capsule and the PCL are

then repaired with the knee extended using bone anchors or detached sutures

according to the site of rupture. If necessary, the direct expansion of the

semimembranosus at the tibia is repaired. Tension the PCL distally with

sutures from proximal to the semimembranosus or tibia or do so proximally

if the femoral attachment is loose. The knee should be stable now in exten-

sion. Advance and retension of the posterior extension of the PMCL (oblique

popliteal ligament) to the semimembranosus corner by closing the posterior arthrotomy, and use multiple sutures for fixation. Advance and retension of the capsular arm to the semimembranosus and advance the semimembra-

Conclusion

Isolated medial-side knee injuries in athletes are usually treated conserva- tively with excellent results. However, in particularly severe cases with valgus

Fig. 5.Superficial medial collateral ligament rupture at the tibial site

Femoral condyle

Capsule tear

at the tibial junction

laxity of 10–15 mm, surgical treatment is suggested. In such patients, the presence of anteromedial rotatory instability could condition functional results. During the operation, surgeons must examine all the various medial structures involved rather than simply repairing the superficial MCL. The posteromedial corner constituted by the PCL, the posteromedial capsule, and the tendinous expansions of the semimembranosus at the tibia to the capsule and the posterior horn of the medial meniscus constitute an important medi- al stabiliser and restriction to internal and external rotation. The posterior horn of the medial meniscus is also a secondary stabiliser to anterior tibial translation in the event of ACL insufficiency but not in cases of meniscotibial ligament and capsule rupture posterior to the tibia. A lack of stabilisation of the posteromedial corner and medial meniscus could cause condyle and meniscal damage secondary to the greater mechanical strain placed on the ACL.

a

b

Fig. 7a, b. Introduction of the suture anchor to repair the medial capsule at the tibial junction

Introduction of the suture-anchor

Repaired of the medial capsule

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