Keywords

Patellofemoral disorders are very common among adolescents and include a number of diseases that are not always easy to identify. Patellar malalignment is a clinical sign frequently observed and represents a generic and multifactorial static anatomical disorder. The direct response to this static malalignment is patellofemoral maltracking, which consists of abnormal sliding of the patella within the trochlear groove during flexion and extension of the knee. This may be reflected on radiological surveys [1]. As a consequence, the patellofemoral relationship is dysfunctional.

Different classifications have been proposed for dysfunctional patellofemoral malalignment. Some are based on the severity of the problem, and others on the mechanism of action or on the onset. The most well-known classification refers to how the patella sets in the femoral groove and has three main categories: patellar tilt, patellar subluxation, and patellar tilt with subluxation [2]. All of these pathological relationships must be confirmed by dynamic studies on transversal plane.

15.1 Patellofemoral Development

The embryonic outline of the lower limb appears at about 28 days of gestation.

A 37-day period then begins the endochondral ossification of the femur, tibia, and fibula together, with early differentiation of the patella and patellar tendon [3]. The secondary centers of ossification of the patella do not appear until 3–5 years of age, depending on sex [4]. The final form of the trochlea is already present in the fetus [5]. Wiberg has classified the patellar facet size into three subtypes [6].

The patella has several functions. First, it allows increasing of the lever arm of the extensor apparatus, improving the action of the quadriceps muscle using the patella as a fulcrum for a better mechanical advantage [7]. The patella also brings together the divergent forces of the four beams of the quadriceps muscle, transmitting the force to the patellar tendon and the tibial tuberosity without friction [8, 9]. Finally, this great sesamoid bone physically protects the cartilage of the femoral condyles from any traumatic frontal impacts and adds to the cosmetic contour of the knee.

15.2 Anatomy

The extensor mechanism of the knee is formed from the quadriceps, its tendon, the patella and the patellar tendon. The normal alignment of this mechanism is in slight valgus, with the apex at the center of the knee. The patella articulates with the femoral groove beginning at approximately 20° of knee flexion, and the contact area between the patella and the femoral groove increases with greater degrees of flexion. The medial and lateral patellofemoral ligaments act as guy wires for statically stabilizing the patella in the sulcus. Medial soft tissue restraints account for resistance to lateral patellar translation in lesser degrees of flexion. At ≥30° of flexion, bony constraint affords patellofemoral stability. In the first degrees of flexion, the patella is superior to the osseous constraints of the femoral sulcus. In particular, the medial patellofemoral ligament (MPFL) acts as the primary soft tissue restraint to lateral dislocation. This ligament extends from the anterior aspect of the femoral epicondyle to the superomedial margin of the patella, lying superficial to the joint capsule and deep to the vastus medialis obliquus (VMO) [10, 11]. The fibers of the MPFL fan out and insert with the vastus medialis tendon. The medial patellotibial ligament (MPTL) acts as a secondary medial stabilizer. MPTL fibers run from the medial side of the tibia, below the joint line and medial to the patellar tendon inserting into the lower pole of the patella [12].

15.3 Patellar Tracking

In normal conditions, the patella slides freely and in a linear fashion in the trochlear groove. In these conditions, the patella follows a toroidal path from extension through flexion. Thus, a great dynamic and multidirectional stability is required. The patellar tracking is influenced by the rotation of the tibia relative to the femur, by the patellofemoral joint morphology and the direction of the tensile force of the quadriceps.

The external rotation of the tibia by 30° of flexion to extension is responsible for the lateral displacement of the tibial tuberosity [9]. This determines an angle subtended between the line of pull of the quadriceps and the direction of the patellar tendon called Q angle. Increased femoral neck anteversion and proximal tibial external torsion makes lateral dislocation of the patella more likely because these conditions generate an increase in the Q angle.

15.4 Patellar Stability

The patella is controlled by the dynamic and static elements of the extensor mechanism and also significantly influenced by torsional and angular alignment of the proximal and distal lower extremity segments. The “dynamic elements” are the four quadriceps muscle proximally, the pes anserinus tendon medially which internally rotates the tibia and the biceps tendon laterally which externally rotates the tibia. The “Q” angle can dynamically change by hamstring activity causing that rotation. The static stabilizing elements of the extensor mechanism are the patellofemoral joint contains and congruency reflected by depth of the sulcus and fit of the patella, in the medial and lateral retinaculum, the medial and lateral patellofemorals ligaments, the medial and lateral patellotibial ligaments and the patellar ligament whose length establishes the height of the patella in relation to the femoral condyles and also transmits the forces of the quadriceps contraction to the tibia. The MPFL is the primary static stabilizer of the patella and prevents it from subluxating or dislocating laterally. Its importance in controlling lateral patellar dislocation has been well documented in several biomechanical studies [13, 14]. Cadaveric studies have shown that 50–60 % of the restraint to lateral translation is provided by the MPFL [15]. The MPTL contributes to 13 % of medial stability [12] and plays an important role as a secondary medial patellar stabilizer [16], helping the patellar tendon to limit upward displacement of the patella during strong quadriceps contraction [17].

The bone conformation of the knee contributes to static patellofemoral stability with the lateral condyle of the femur more prominent than the medial condyle. This limits lateral displacement of the patella. The femoral sulcus is flattened at its proximal part, becoming deeper in the distal portion. Therefore, it is more likely that dislocation of the patella will occur in extension or early flexion.

Dynamic forces include the quadriceps muscle and specifically the medial structures (VMO) that control the movement of the patella during the full range of motion, preventing lateral dislocation especially in early flexion. All conditions that weaken the stabilizing action of the vastus medialis may predispose to lateral dislocation of the patella. Other muscle groups (hamstrings, gastrocnemius-soleus, ankle and foot flexors and extensors) indirectly participate to the stability of the extensor mechanism of the knee [18].

15.5 Clinical Assessment

Malalignment of the lower limbs should be looked for during clinical examination. When lower limb malalignment is present, it generally is associated with patellofemoral malalignment. Skeletal changes of the static balancing of the lower limbs, even on the frontal and sagittal planes, need to be carefully recognized to assess their impact on the patellofemoral relationship. The first assessment should be performed on a standing patient to check for abnormalities of the axis of the lower limbs, like valgus or varus knee or torsional defects. The affected limb should always be compared with the contralateral extremity. The physiologic varus or valgus deformity that occurs during skeletal growth is generally bilateral and symmetrical. Normal knee alignment changes as a child grows. Measuring the femoral–tibial angle in standing and supine positions assesses the presence of a varus or valgus deformity. A varus angle between 10 and 15° is normal in neonates. The femoral–tibial alignment becomes neutral between 14 and 20 months of age, to a maximum valgus of 10–15° by 3–3½ years of age. The normal femoral–tibial alignment of 5–7° is achieved between 6 and 8 years of age. Genu varus (bowlegs) is assessed for by placing in contact the two medial malleoli and measuring the distance between the femoral condyles. Genu valgum (knock knee) can be assessed for in the supine position by measuring the distance between the medial malleoli, with fully extended knees and the patellae facing upward and the medial femoral condyles in contact. The examiner must define the alignment in the sagittal plane to focalize a genu recurvatum or procurvatum. On the axial plane, torsional defects of the lower limbs may be present. The term “torsion” refers to a rotational change between the epiphysis of a bone. These torsional defects can be isolated or, more frequently, combined. The most common types of torsional defects in children are increased femoral anteversion combined with proximal or distal tibial external torsion (Fig. 15.1). In the coronal plane, femoral anteversion is defined by the angle of the femoral neck in relation to the femoral shaft. Children with isolated increased femoral anteversion have an intoeing gait that becomes evident when running. In the prone position, there is an excessive internal rotation of the hip and decreased external rotation. In the standing position with full extension of the knees and the feet aligned, the legs appear bowed and “squinting patellae” are present. Typically, the child plays sitting on his knees with the lower legs positioned laterally relative to the thighs (“frog-like position”). In most cases, the tendency to intoe becomes less evident as the femoral anteversion decreases or, in other cases, as the external tibial torsion increases.

Fig. 15.1
figure 1

Lower limbs malalignment in mother (35 years old) and child (6 years old). Increased anteversion of the femoral neck associated with tibial external rotation. In standing position in full extension of the knee with the feet aligned the legs appear bowed and a squinting patella is present. When the patella is maintained on coronal plane, external tibial torsion becomes clear

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Isolated tibial torsion, internal or external, is observed during skeletal growth. Tibial rotation can be cause of intoeing or outtoeing in children up to 3–4 years of age. Internal tibial torsion is a cause of intoed walking in childhood. In this case, patients sit down on their feet. At clinical examination, the lateral malleolus lies anterior to the medial malleolus and, in the standing position with front-facing patellae, internal rotation of the legs and feet is evident. The amount of lateral tibial torsion increases from about 5° at birth to an average of 15°/20° at maturity. Therefore, spontaneous improvement is often due to physiological skeletal growth.

Isolated external rotation of the tibia is less frequent. The child walks with the feet turning out. In the standing position with the feet aligned, the kneecaps present a convergent squint. The frequent association of marked anteversion of the femur with increased external tibial rotation can be characterized by intoeing of the knee with right assessment of the foot. The child will sit down in a frog-like position showing the disharmonic circling of the legs during running.

The presence of lower limbs malalignment associated with an abnormal patellofemoral relationship associated constitutes a diagnostic and therapeutic problem that is not always easily solved in adolescents. A complete and careful diagnostic pathway should precede any form of treatment.

15.5.1 Physical Examination of the Knee

The examiner can visually observe a squinting patellae or a bayonet deformity of the patellar tendon. With the patient sitting with his legs held out of bed, it is possible to evaluate the appearance of the patellae. In particular, cases of high patellae can be seen by examining the knees frontally. If also associated with a patellar tilt, it is possible to appreciate a squinting patella that appears like the “eyes of a grasshopper.” Examination in the upright position allows evaluating the clinical Q angle between a line drawn from the anterior superior iliac spine and the center of the patella, and from this to the tibial apophysis. In a lateral view, a deformity of the sagittal profile of the knee that seems like a “camel” is frequently associated with high patella. The examination should be extended at the presence of a prominence of the anterior tibial apophysis as observed in case of Osgood–Schlatter disease. In the supine position, great attention must be given to examination of the knee (Fig. 15.2). The measure of the Q angle is repeated, and patellar tracking is checked during full flexion and extension. On palpation, patellofemoral ligament insufficiency must be ruled out and points of pain accurately monitored. Finally, it is necessary to search for all signs that may indicate a patellofemoral problem with the Fairbanks apprehension test [19], the patellar tilt test and the Glide test [20]. During the examination, the possible presence of a valgus hindfoot or equinus deformity of the foot, which could cause alterations on patellar tracking, must also be sought. An associated pronation of the foot should be assessed for when the patient is walking. A prolonged half-squat test can evoke anterior knee pain (AKP). The comparative analysis of both lower limbs is essential and can attest to the presence of hypotrophy of the quadriceps.

Fig. 15.2
figure 2

Knee of a 12-year-old female suffering from recurrent patellar dislocation. In conditions of muscle relaxation, the patella appears normal (a), while the isometric contraction of the quadriceps muscle (b) pulls the patella laterally and patellar subluxation becomes evident

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15.5.2 Symptoms and Signs

Anterior knee pain is one of the symptoms that appear either isolated or combined with other symptoms. It is important to underline that a knee pain of a pediatric patient is hip pain, until proven otherwise. A more typical assessment concerns symptom characterization. When pain is isolated, it is typically undefined, poorly localized and may be exacerbated by prolonged sitting position with knee flexed, climbing the stairs, squatting or changing direction. Patients indicate the entire front of the knee as the focus of discomfort. This complaint is frequent in females. In the absence of true chondromalacia, it is unlikely to find true joint swelling, although the patient may report a sensation of a bloated knee.

Sometimes the patients may complain of a feeling of the knee “catching” or pseudolocking, which is usually transient. In these cases, it is very important to differentiate this from other causes of joint block (meniscal lesions and osteochondritis dissecans). Patients should be questioned about feelings of instability. In fact, pain is often one of the clinical signs in cases of patellar instability, especially if associated with a secondary chondromalacia.

15.6 Instrumental Assessment

Using clinical findings alone, diagnosis may be elusive in some instances. The identification and classification of symtomatic patellofemoral malalignment requires visualization of the patellofemoral joint in early flexion, because the patella has a tendency to line up in the trochlear groove at flexion over 25–30°, even in the cases of patellofemoral malalignment. Moreover, considering that maltracking is a dynamic condition, radiographic assessment should focus on the dynamic phase. For this reason, routine anteroposterior, lateral and axial views are not specifically useful.

Therefore, if patellofemoral maltracking is clinically suspected, the adolescent knee is submitted to static and the dynamic computed tomography (CT). The static CT provides complete information about the patellofemoral relationship [2], the morphology of the femoral condyles and trochlear groove, the distance in the frontal plane between the apex of the tibial tuberosity and the bottom of the trochlear groove (TTTG) and also allows evaluation of the height of the patella. During dynamic isometric quadriceps contraction, the behavior of different types of patellofemoral malalignment (improvement and unmodified or worsening) [21] is clarified, and this confirms the observations of the past [22], when it was stressed the importance of the dynamics to various forms of instability (subluxation and dislocation).

If the knee pain is associated with the CT evidence of patellar tilt alone, it may be attributed to an excess of stability and then compatible with lateral patellar compression syndrome. In other circumstances, the knee pain is associated with CT evidence of patellar subluxation or subluxation and tilt, being only one of the symptoms of different degrees of patellar instability. The recent introduction of dynamic MRI will soon replace the use of static and dynamic CT [23].

15.7 Lateral Patellar Compression Syndrome

The syndrome is generally characterized by AKP. The patella tends to move laterally while remaining stable during the full range of motion. The lateralization forces determine the loss of the balance of the extensor mechanism of the knee resulting in a pathological shift of the patella to the lateral femoral condyle [18]. Listen carefully to the patient and correctly interpret the characteristics of the pain is always the best way to address the diagnosis.

Clinical examination is critical in the diagnosis. The tightness of the lateral retinaculum should be sought to confirm the suspicion. With the patient in a supine position, the inability to elevate the patella medially over the tangent plane of the femoral condyles (passive patellar tilt test) gives evidence of a retraction of the lateral retinaculum. With the knee flexed at 20–30° degrees, it should be possible to push the patella medially more than one-fourth of the patellar width (Glide test) [20]. The lateral retinaculum is tight if the patella moves medially less than this distance. Clinically, there are no signs of instability. Radiographic examination with axial views at different degrees of flexion has various limits like the difficulty of evaluation with quadriceps contraction, the absence of a defined reference plane for measurement, the overlapping of images and no detection of minimal rotational malpositioning [21]. CT scan and, recently, MRI are much more useful, because they allow the documentation of patellar tilt that does not improve or worsen during the dynamic test with quadriceps contraction. Conservative treatment is the first choice [24]. Rest, immobilization with brace and, occasionally, the use of anti-inflammatory drugs can sometimes be helpful. However, rehabilitation is the basis of therapy. The exercises aim to loosen the retracted lateral structures and to strengthen the medial dynamic stabilizers (vastus medialis oblique and adductors) and to restore the balance of the extensor apparatus. Surgical treatment should be considered if conservative therapy fails. When this occurs, lateral retinacular release is indicated. Sectioning of the lateral retinaculum must be accurate and complete, taking care not to leave any residual fibers in tension. At the end of the intervention, it is necessary to verify the ability to push the patella medially over two quadrants with the knee flexed at 30°. Postoperative rehabilitation starts as soon as possible in order to avoid scar tissue formation, but return to sports activities should be avoided for at least 3–4 months after surgery.

15.8 Patellar Instability

Patellar instability is a frequent condition in children and adolescents. The instability is a dynamic clinical state that in 20 % of patients is secondary to a direct blow, whereas in a high percentage of cases is possible to individualize the presence of predisposing factors which alter the normal patellafemoral function. Both subluxation and patellar dislocation (acute or recurrent) are different degrees of patellofemoral instability syndrome.

15.8.1 Acute Patellar Dislocation

Acute patellar dislocation is the most common acute knee injury in active children and adolescents, and it may lead to functional disability and failure to return to full sports participation. The majority of injuries occur in the early adolescent age group. The incidence of primary patellar dislocation is 5.8 per 100,000, increasing in adolescents to 29 per 100,000 [25]. About 60 % of acute dislocations in younger patients occur during physical activity. The most common activities in which these injuries occur are ball sports (football, basketball, and baseball), accidental falls and gymnastics.

Traumatic patellar dislocation causes a high incidence of injuries to the MPFL. MPFL injury patterns in skeletally immature patients are different from those skeletally mature patients. The most frequent anatomical site of complete MPFL lesions in children and adolescents is the patellar attachment. The patellar insertion remains cartilaginous until 16–18 years of age, in contrast to the distal femoral attachment, making it more vulnerable and favoring avulsion fractures associated with MPFL tear rather than MPFL tear only [26]. Traumatic patellar dislocation may result in an osteochondral fracture in about 5 % of cases [27]. These are from either the lateral femoral condyle or from the patella itself, usually caused by shear forces induced by contraction of quadriceps muscle at the lateral femoral condyle during the relocation of the dislocated patella.

A complete medical history and careful clinical examination, supplemented with imaging, are essential to define the type and severity of dislocation and the presence of predisposing factors in order to plan the most appropriate treatment.

15.8.2 Mechanism of Injury

Indeed, the purely traumatic patellar dislocation is not frequent. Usually, the etiology includes predisposing factors. Up to 80 % of patients sustaining patellar dislocation have anatomic variables that predispose to lateral instability [28]. High patella, trochlear dysplasia, hyperlaxity, an increased quadriceps angle due to various torsional deformities of both the femur and the tibia, female gender, and a positive family history have all been associated with patellofemoral dislocation [25, 27, 29–31]. Acute patellar dislocation may occur from either a direct or indirect mechanism of trauma. Direct injuries result from a medial blow to the patella, which forces it laterally. Indirect trauma is more common and involves a valgus force with the foot fixed to the ground and either internal rotation of the femur or external rotation of the tibia. In this position, common in sports, the Q angle is increased and contraction of quadriceps pulls the patella laterally, exceeding the tensile strength of the MPFL. The direction of dislocation is typically lateral. Medial dislocations are uncommon and usually iatrogenic [32].

15.8.3 Clinical Presentation

At the time of initial evaluation, patients frequently report a “giving way” or “going out of joint” sensation during twisting movements of the knee. Usually, the patella has spontaneously relocated before the patient presents to the physician. On the rare occasion when the patella remains dislocated at initial evaluation (fewer than 20 % of cases), the knee is in the flexed position, and the patient has significant pain and swelling with extreme apprehension. The femoral condyles are readily palpable medially, and the patella is visualized laterally as a mass. In this case, extension of the knee will reduce the patella. The injured knee is initially examined in extension. In the acute setting, patients will often be tender in all areas of the knee, so palpation is not always useful. Later, palpation allows to identify the specifically injured areas. The physician should assess the retinacular structures, ligaments and joint lines for swelling or tenderness. After a first episode of dislocation, hemarthrosis will rapidly develop. Tenderness, often accompanied by significant medial ecchymosis, is usually encountered over the medial origin of the MPFL at the adductor tubercle or along the medial facet of the patella. If arthrocentesis reveals fat droplets in the joint fluid, an associated osteochondral fracture should be suspected. Attempts to displace the patella laterally will be prevented by the patient’s apprehension.

The contralateral knee should be examined for the presence of predisposing factors. An examination of knee stability is also essential to exclude ACL injuries. The differential diagnoses include acute sprain of the medial collateral ligament, avulsion of tibial eminence, isolated osteochondral fractures, and rupture of the quadriceps or patellar tendons.

15.8.4 Imaging

With a suspected diagnosis of acute patellar dislocation, radiographic assessment should include anteroposterior, lateral and tangential views of both knees, according to the Merchant technique, in which the knee is supported at 35–45° of flexion to allow evaluation of the patellofemoral joint [33]. These radiographs may show displacement or residual lateral placement of the patella because of the disruption of the medial stabilizers (Fig. 15.3), but in most cases, the patella is reduced.

Fig. 15.3
figure 3

X-ray examination of a skeletally immature patient (13-year-old girl) showing acute lateral dislocation of the patella

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Anteroposterior views allow evaluation for the presence of possible osteochondral fragments from the medial patellar margin or the lateral femoral condyle. The lateral view allows for assessment of a high patella, based on the Insall–Salvati ratio. Oblique and notch views may be necessary to identify any loose bodies or osteochondral defects, although a significant number of these injuries are missed on plain radiographs. Stanitski el al correlated arthroscopic and radiographic findings in 48 adolescents with acute patellar dislocation. Only 23 % of these had an osteochondral lesion detected by radiographs, whereas arthroscopy found chondral or osteochondral injury in 71 % [33].

MRI is routinely indicated after acute patellar dislocation. Advancements have greatly improved the imaging capability of MRI for detecting soft tissue injury to the MPFL with a sensitivity of 85 % and an accuracy of 70 % [15, 34]. MRI is also useful for detecting chondral and osteochondral lesions and can help both diagnosis and evaluation of the extent of injury (Fig. 15.4). The classic MRI findings in acute patellofemoral dislocations include focal impaction injuries of the lateral femoral condyle, osteochondral injuries to the medial facet and medial retinacular injuries. “Kissing lesion” bone bruises on the lateral femoral condyle and the medial patella result from lateral dislocation of the patella and its relocation. MRI may also demonstrate inflammation around the VMO and may show MPFL tears or avulsions [34]. CT scans can be useful in the acute setting for assessing the presence of osteochondral detachment.

Fig. 15.4
figure 4

The MPFL tear with an osteochondral fragment avulsed from patellar insertion at MRI study (from [38], with permission)

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15.8.5 Treatment

Most patients present with the patella reduced and rarely require reduction by the physician. Arthrocentesis of the joint can be performed to reduce pain. Management of the first episode of patellar dislocation is still up for debate but the conservative approach continues to be the most common, except in the presence of osteochondral lesions. Normalization of the strength and function of the quadriceps remains the gold standard of conservative treatment. After a brief period of immobilization in extension with protected weight bearing (5–10 days), the patient should initiate quadriceps isometrics, straight leg raises and single plane motion exercises. It is important to recover the entire quadriceps muscle in the strengthening program despite the traditional teaching, which focused primarily on the vastus medialis. As symptoms allow, the patient can progress to running and then ultimately advance to sport-specific activities.

Patellar taping and bracing have been performed as adjunctive non-operative rehabilitative techniques to medialize the patella, but recent studies have shown that they provide only symptomatic relief without actually medializing the patella [35]. However, despite the fact that a recurrent history of patellar dislocation in children and adolescents after conservative treatment has been reported to be benign, a significant number of patients will experience chronic instability, redislocation, or chronic patellofemoral pain. After non-operative treatment, redislocation rates range from 15 to 71 % [15, 25, 36]. The cause of this high frequency of redislocation is found not only in a persistent insufficiency of the MPFL secondary to its tear, but also in the presence of predisposing factors [28]. For this reason, direct reconstruction of the MPFL did not give better results than conservative treatment [25, 37]. The role of the MPFL as a guide for a static stabilizer of the patella in the sulcus was better defined [38]. In fact, biomechanical research has demonstrated that the MPFL accounts for 50–60 % of the medial soft tissue restraining force against lateral patellar subluxation or dislocation [12, 14, 39, 40]. Because of its specific function, the focus on reconstruction of the MPFL has increased in recent years. Different techniques are proposed for MPFL reconstruction, with greater attention on minimally invasive surgical approaches and respect for esthetics [16, 25, 37, 38, 40]. In addition, even MPTL insufficiency, which antagonizes the lateral displacement of the patella in measure of 13 % of patients, can facilitate redislocation [12].

Indeed, the MPTL plays an important role as a secondary medial patellar stabilizer [16], helping the patellar tendon to limit upward displacement of the patella during strong quadriceps contraction [17]. So in the presence of predisposing factors for instability such as high patella, severe Q angle (>15°), increased tibial tubercle-trochlear groove distance (TT-TG > 1.2 cm), trochlear dysplasia and hyperlaxity, the reconstruction of both the MPFL and MPTL, by combined use of ST and G, allows to achieve greater stability [41]. This approach avoiding physeal plate is utilized for recurrent dislocation of the patella and described later [38].

While surgical treatment for acute patellar dislocation remains controversial, in cases of osteochondral lesions, surgical reconstruction of the MPFL and MPTL with cartilaginous defect repair is accepted and considered the gold standard. Osteochondral fragments can be managed with either an arthroscopic approach or through a small arthrotomy. The osteochondral lesion detaches from the lateral femoral condyle or the patellar articular surface. The central and medial patellar facets are the most frequent site of injury. An arthroscopic examination allows the surgeon to accurately determine the size of the fragment, the extent of subchondral bone on the fragment, the anatomic location of the fragment and the need for fixation. The loose fragment is often far from its origin and is most easily retrieved and positioned near its bed with the arthroscope than during an arthrotomy.

Surgical management of an osteochondral fragment is critical to long-term prognosis of knee joint function. There is other treatment of choice for osteochondral lesions. Whenever possible, fragments >1.0–1.5 cm in diameter should be replaced and stabilized with headless compression screws or absorbable pins, which provide stable fixation and compression of the fragment and permit early joint motion. Microfractures, drilling, osteochondral grafting, or autologous chondrocyte implantation may be considered for various cases. More often, the bone is thin and does not allow a firm fixation. In these cases, arthroscopic removal is preferable. Postoperative management includes knee brace immobilization for 4 weeks with protected weight bearing, followed by early physical therapy for range of motion and strengthening exercises.

15.8.6 Recurrent Patellar Dislocation

In younger patients, the rate of recurrent dislocation is higher than in patients over 20 years of age [36]. These patients have frequently had a first episode of acute dislocation of the patella, and patient history is often sufficient to guide the diagnosis. Several abnormalities are responsible for this severe degree of instability in a high percentage of cases: flattened or hypoplastic lateral femoral condyle, hypoplastic or high patella, trochlear groove dysplasia (short and shallow), axial (genu valgum) and sagittal (genu recurvatum) deviations or torsional deformities of the legs (excessive femoral anteversion or external tibial torsion), lateral offset of the tibial tuberosity, generalized ligamentous laxity and contracture dysfunction of the vastus lateralis [25, 27, 29–31]. These combined anatomic and constitutional factors predispose to patella maltracking with recurrent lateral dislocation, especially in early flexion.

15.8.7 Physical Examination

From a clinical point of view, recurrent patellar dislocation may manifest as repeated episodes of patellar dislocation or, become evident after a history of AKP associated with instability symptoms. A complete medical history and careful clinical examination are essential to define the type of dislocation and should be supplemented with imaging. Clinical examination should include everything stated above for the evaluation of patellofemoral joint disorders.

15.8.8 Imaging

The use of conventional axial views at 20–30° of flexion (Laurin views), posteroanterior weight-bearing views of both knees at 45° flexion, lateral views and Merchant views are all often used in cases of recurrent patellar dislocation. However, it is preferable to use static or static and dynamic CT study [21] and MRI, which are now considered reliable methods of identifying risk factors for chronic patellar instability [23] especially in pediatric and adolescent patients. These images show different degrees of subluxated patellae or tilted and subluxated patellae.

15.8.9 Treatment

Conservative treatment based on a physical therapy program should be pursued to decrease the frequency of episodes of patellar instability. However, if the quality of life is undermined and expectations related to sports are disappointed, surgical treatment must be considered. In this case, the patella must be studied with imaging: often a subluxated or tilted or only subluxated aspect on static CT worsens during dynamic study. The choice of surgical procedure is closely related to the skeletal age of the patient, the severity of instability, the patient’s sports performance and especially to any factors predisposing to instability.

In growing patients, physeal-sparing procedures are recommended. The aim of treatment for patellar instability should be to prevent repeated episodes of dislocation, give the patient the feeling of stability during activities, regain good joint function, reduce the patient’s risk of injury and, preserve the esthetic appearance of the knee and reduce hospitalizations. Several techniques have been proposed for the surgical treatment of recurrent patellar dislocation in adolescents.

The distal bony realignment of the tibial tubercle is not recommended in skeletally immature patients because it can induce premature physeal closure and subsequent genu recurvatum. However, some authors have utilized distal periosteal patellar tendon realignment, either partial, as described by Goldwaith in 1904, or total, as suggested by Dal Monte in 1979 and Ippolito in 2011 [42].

In 1922, Galeazzi described an effective technique for physeal-sparing MPTL reconstruction with the semitendinosus tendon. The purpose of this technique is to direct the pull of the quadriceps in line with the intercondylar notch of the femur. This aim is also reached in reconstructing the MPTL, which contributes to establish the height of the patella in relation to the femoral condyle and also transmits the force of the quadriceps contraction to the tibia [43]. This technique was adopted and modified by Fiume in 1954, who added lateral retinacular release and medial retinacular reefing. In 1972, Baker adopted this technique but made an oblique mediolateral tunnel across the patella.

The technique requires a preoperative arthroscopic evaluation to assess for the presence of meniscal or cartilage defects. The operation is performed with the patient in a supine position, using a pneumatic tourniquet applied to the proximal thigh. A medial longitudinal parapatellar incision is made to expose the extensor apparatus. A lateral release is performed, taking care to avoid tearing the synovial membrane. After the semitendinosus tendon is identified, it is divided at the muscle–tendon junction. The tendon must be at least 12–13 cm long. An oblique 4-mm hole is drilled through the patella from the inferomedial to the superolateral side, and the tendon is passed through it from the medial to the lateral. After firmly drawing the patella medially and downward to reposition it in the trochlea, the tendon is sutured with considerable tension (Fig. 15.5). Successively the lax medial retinaculum is reefed. The knee is immobilized in a 20° flexion brace for 3 weeks. Postoperative CT scans are routinely performed to check for overcorrection, which can lead to development of a medial patellar subluxation [42]. Isometric muscle exercises of the quadriceps are started in a brace the day after the operation. Once the immobilization device is removed, continuous passive motion of the knee and volitional exercises, combined with neuromuscular electrical stimulation are started, along with exercises to strengthen the quadriceps and hamstring muscles. One month after surgery, the patient can begin knee flexion of more than 90° and progressive weight-lifting until normal function is reached. Sports activities should be avoided for 4–6 months.

Fig. 15.5
figure 5

Galeazzi’s semitendinosus tenodesis modified by Baker. The semitendinosus tendon was passed through the patella in an oblique tunnel and was sutured to itself. After finding the right tension and obtaining a repositioning of the patella medially and downward, the operation is completed by lateral release and medial retinacular reefing

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In the author’s experience, with 4 years of follow-up, Galeazzi’s semitendinosus tenodesis modified by Baker, with adequate lateral release and medial retinacular reefing, produces good clinical mid-term results in skeletally immature patients [44]. Other studies have reported unsatisfactory results at long-term follow-up [43].

Three important factors that may influence of Galeazzi’s technique results have been reported: appropriate tension before suturing the tendon to the patella, adequate lateral release and a normal joint surface of the patella at the time of surgery [30]. The data obtained with static CT at follow-up showed that the patella reached a satisfactory congruence with the trochlea in all knees that were subluxated and tilted prior to surgery [44]. However, dynamic CT showed that this technique is unable to counter the tendency of upward displacement of the patella, or to prevent subluxation and tilting of the patella in patients with high patella preoperatively [44]. The maintenance of this malalignment in dynamic conditions could lead to a risk of chondromalacia and perhaps explains the poor results reported by other authors at long term follow-up [45]. These results require the development of new technical solutions. In recent years, it has been published that the MPFL accounts for 50–60 % of the medial soft tissue restraining force against lateral patellar subluxation or dislocation [15], and this has increased interest in surgical reconstruction of the MPFL alone [39, 46]. Even if the indications for the reconstruction of the MPFL are not yet fully clarified [47], it may reach good results alone in the absence of predisposing factors for instability. However, the presence of an excessive Q angle or a high patella may complicate the outcome of this technique, as suggested by Mountney [48]. This report stated that patellofemoral joint stability problems are rarely straightforward and may be influenced by other factors such as articular geometry, alignment of the lower limb, rotational deformities, patellar height and ligamentous laxity [48]. Because of these considerations, the presence of a high patella, a high Q angle or other risk factors should put to increase stability and obtain better results at follow-up [25, 39, 40, 49] reconstructing both MPFL and MPTL.

The choice to reconstruct both the MPFL and MPTL ligaments is based on the reported importance of the MPFL as a primary medial patellar stabilizer [13, 14, 50] and of the MPTL as an accessory stabilizer [16] and patellar height regulator during strong quadriceps contraction [17]. The use of combined MPFL/MPTL reconstruction using the ST tendon and G autograft augmentation contributes to maintain patellar stability in opposition to the stress occurring during the growth period. This neo-ligament consisting of two tendons gives greater resistance against to ligamentous laxity and to the high patella and/or abnormal TTTG that often characterize recurrent patellar dislocation in skeletally immature patients. The surgical technique (Fig. 15.6a and b) requires a preoperative arthroscopic evaluation to assess for the presence of meniscal or cartilage defects and involves four mini-incisions. First, a transverse skin incision is made medial to the anterior tibial apophysis to identify the insertion of the pes anserinus tendons. After dissection, the harvested semitendinosus and gracilis tendons are sutured, preserving the distal insertion site. A second mini-incision is made just medial to the inferior patellar apex. An additional 2-cm incision is made at the superomedial border of the patella. A longitudinal 2-mm Kirschner nail is driven into the medial third of the patella. A distal-to-proximal intraosseous longitudinal, 4-mm diameter tunnel is created. Once the tunnel is expanded to a diameter of 4.5 mm, the ST and G tendons are passed over the tibial growth plate and through the soft tissue and are brought distal to proximal into the patellar tunnel. A fourth skin incision is made to expose the femoral adductor tubercle. The proximal portions of the ST and G tendons are tunneled into the medial parapatellar subfascial soft tissue. The ST and G tendons are tensioned at 30°–45° of flexion [44] and fixed at the middle of the edge of the adductor tubercle of the medial femoral condyle by a titanium suture anchor (Arthrex Corkscrew suture anchor with needles: 5 × 12.1 mm with two size-0 fiber wires). The ST and G autografts are secured to the periosteum of the proximal pole of the patella with a bioabsorbable suture. Patellar stability is checked in full knee extension, allowing congruent smooth tracking of the patella. The knee is then positioned in a 20° flexion brace for 3 weeks. Postoperative CT scan is performed to check for overcorrection. Isometric quadriceps muscle exercises are started in the brace the day after surgery. Once immobilization is removed, controlled passive motion of the knee and neuromuscular electrical stimulation are started, along with quadriceps and hamstring muscle strengthening exercises. One month after surgery, knee flexion of more than 90° and progressive weight bearing are allowed. Sports activities are restricted for 4–6 months. The technique, which does not require a lateral release and/or medial retinaculum reefing, is in continuity with Galeazzi’s procedure but also represents a theoretical and practical improvement to it.

Fig. 15.6
figure 6

Combined MPFL/MPTL reconstruction by ST tendon and G autograft augmentation by mini-incisions: a the harvested semitendinosus and gracilis tendons prepared preserving the distal insertion site with longitudinal 2-mm Kirschner nail driven into the medial third of the patella (from [38], with permission); b the proximal portions of the ST and G tendons are passed into the 4 mm longitudinal patellar tunnel avoiding tibial proximal growth plate, tunneled into the medial parapatellar subfascial soft tissue, tensioned at 30° to 45° of flexion and fixed in the medial condylar femoral insertion area of MPFL by a titanium suture anchor (from [38], with permission)

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However, if the predisposing factors for patellar instability could exceed the strength carried by the ST and G tendons during growth, at the end of skeletal growth, distal non-physeal-sparing alignment techniques could be adopted to perform a definitive surgical correction.

15.9 Anterior Knee Pain

Anterior knee pain is a non-specific symptom commonly seen in the pediatric and adolescent populations and should be considered a “working diagnosis” until a specific diagnosis is made [1]. Several causes may create AKP and the correct clinical approach is “always looking for the cause.” If a child reports knee pain, hip pathologies typical for the age should be ruled out first [synovitis, slipped capital femoral epiphysis, Legg-Calvè-Perthes disease, necrosis of the femoral epiphysis, tumors, juvenile idiopathic arthritis (JIA)]. Articular disorders that may occur with AKP are divided into four subgroups: (1) intra-articular disorders (a) synovial causes (trauma, JIA, plica syndrome); patellar causes (patellar lateral pressure syndrome, chondromalacia, chondral lesions, osteochondritis dissecans, shape dysplasia); (b) intercondylar notch causes (fat pad, ganglia, hematoma, ruptured ACL); (c) femoral causes (osteochondritis dissecans); (2) extra-articular disorders (capsule, collateral ligaments, subcutaneous tissues, retinacular stress) [51], Fig. 15.7, tendons and/or apophysis (Osgood–Schlatter, Sinding-Larsen-Johansson, patellar tendinitis, iliotibial band tendinitis), quadriceps atrophy; (3) articular disorders (reflex sympathetic dystrophy, chondroma, osteoid osteoma); (4) para-articular disorders (benign and malignant tumors).

Fig. 15.7
figure 7

Histological appearance of retinacular nerve excised for biopsy during a lateral release procedure. Nerve demyelination and fibrosis are highlighted, similar to those typical of Morton’s interdigital neuroma (personal observation)

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The surgical treatment of a patient with AKP must be performed after the whole diagnostic algorithm. Anterior knee pain can be attributed to lateral patellar compression only if patellofemoral malalignment (usually a tilt) is documented. If a specific cause cannot be found for the adolescent’s anterior knee pain, it is defined as idiopathic.