In children and adolescents, a number of conditions involving this region have been described. They are treated by attempting to improve the basic biomechanical forces.

Chondromalacia is a nonspecific term that refers to the appearance of softening and degeneration of the patellar cartilage. Patellar subluxation refers to partial lateral displacement of the patella. The terms patellofemoral stress syndrome, patellar malalignment, and excessive lateral pressure syndrome refer to the abnormal mechanics causing stress concentration and pain.

The quadriceps-patella mechanism is in valgus, as measured by the Q (quadriceps) angle from anterior superior spine to patella to tibial tubercle. Possible factors contributing to patellar pathology include increased valgus of the knee, increased anteversion of the femur or external torsion of the tibia, a high patella (patella alta), abnormal shape or development of the quadriceps, or flattening of the femoral groove. Underdevelopment of the medial side of the quadriceps restraints contributes to subluxation or dislocation. Females normally have slightly greater valgus of the knee than males. Cartilage degeneration occurs beginning in the deep layers and becoming visible later.

Clinically, patellar problems cause symptoms of aching in the anteromedial region of the knee. This is usually worse with stair-climbing or prolonged sitting because flexion increases patellofemoral force. Crepitus may be felt, but this may be painless in some patients and is not in itself pathologic. “Catching” or “locking” may be noted. A feeling of “giving way” may be related, especially with subluxation of the patella. On physical examination, the most reliable way to test patellar tenderness is by direct compression of the patella against the femur. Palpation under the patella is not diagnostic. Effusion is present only if patellar degenerative changes or extreme overuse have occurred. In most cases, there is no effusion. Reproducing patellar subluxation by laterally directed pressure may produce apprehension (the apprehension test). Radiographs are usually nonspecific, but occasionally lateral displacement or tilt of the patella may be seen on the sunrise view.

Patellofemoral stress disorders are common between the ages of 10 and 20 years, but often become less bothersome after these years and do not usually progress to arthritis.

Differential diagnosis includes a synovial fold or plica, a medial meniscus tear, tendinitis of the quadriceps or patellar tendon, and osteochondritis dissecans of the patella or distal femur.

Treatment consists of decreasing activities performed with knees flexed, such as stair-climbing and prolonged sitting. Temporary rest from sports and use of nonsteroidal antiinflammatory agents may be necessary. Exercises to strengthen the medial (stabilizing) part of the quadriceps include extension from 0 to 30 degrees, by lifting weights within this range or extending the knee on a pillow to compress it. Muscles should be stretched if they are tight. Arch supports may help if flexible flat feet are contributing to tibial torsion. Surgical measures are rarely needed, but they include release of a tight lateral patellar retinaculum, medial soft-tissue tightening, tibial tubercle transfer, or correction of valgus, anteversion, or patella alta. These all produce satisfactory pain relief in 75% to 90% of cases.

Patellar dislocations may be acute or recurrent. The patella usually dislocates laterally. An acute dislocation is associated with significant swelling and medial knee pain, and follows valgus or rotating force. This should be treated for 4 to 6 weeks with the knee extended, using a knee immobilizer, except in cases with bony avulsion. Recurrent subluxation is common; the patient has less pain and swelling, and subluxation often occurs during everyday activities. A realignment operation as described earlier is the only effective way to stop frequent and bothersome episodes.

Osgood-Schlatter disease, patellar tendinitis (jumper’s knee), and quadriceps tendinitis are all manifestations of excessive, repetitive stresses on the extensor mechanism. They are listed in order of decreasing frequency in children.

Osgood-Schlatter “disease” is a traction-induced inflammation of the tibial tubercle, not really a disease. Rather, it is a reaction of the bone and growth cartilage of this region to repetitive stress. The tibial tubercle is a distal extension of the proximal tibial epiphysis. It develops an ossification center between ages 9 and 12, but does not completely ossify until ages 15 to 17 years. It is within this age range that repetitive stresses can gradually deform the tubercle, causing enlargement of the tubercle and local inflammation. Tenderness and swelling are localized to the tubercle only and do not extend to the joint. Running, jumping, or kneeling exacerbates symptoms. Treatment involves decreasing activity to a level at which symptoms are minimal, occasionally using a knee immobilizer, crutches, and ice after activity in severe cases. The patient may be vulnerable to recurrence for up to 2 years until the tubercle matures. If he or she is educated about this likelihood, individual regulation of activities can be effective. Complete avulsion of the tubercle is extremely rare and seems more related to sudden stress than to apophysitis.

Patellar tendonitis, inflammation at the origin of the patellar tendon (at the inferior pole of the patella), is related to the same type of overuse as Osgood-Schlatter apophysitis. It is most often seen in basketball players, and is therefore known as jumper’s knee. Pain present during both rest and activity is more worrisome than pain occurring just after activity. Treatment is the same as for Osgood-Schlatter disease. Warm packs before and cold packs after activity may also be of help. Rarely, pain may occur at the proximal pole of the patella and is termed quadriceps tendinitis.

Popliteal cysts in children are localized on the medial side of the popliteal region (Fig. 105-5). They occur most commonly in boys younger than age 9 years. Unlike popliteal cysts in adults, these cysts in children are usually not associated with any intraarticular pathology (17), and they usually regress spontaneously with time. The recurrence rate is higher after surgical excision than after observation. The origin of these cysts is a slitlike communication through the joint capsules between the knee joint and the gastrocnemius-semimembranous bursa on the medial side of the popliteal region.

These cysts often present as tumors but can usually be differentiated clinically by their characteristic location, firm consistency, discrete encapsulation, and slight mobility. Transillumination is helpful because the whole contents of the mass lights up when the room is darkened, distinguishing it from a blood-filled or a solid tumor. Biopsy should rarely be necessary.

A discoid meniscus is an acquired flattening and deformation of the normally semilunar lateral meniscus. In some cases, this flattening occurs because of the absence of normal peripheral attachments. Symptoms such as pain, clicking, and locking often develop in the absence of trauma in children from age 2 to adulthood (18). The meniscus should be trimmed or excised if symptoms become severe.

Bowed leg or genu varum of up to 20 degrees is normal in children until the age of 18 months. Bowing normally does not increase significantly after walking begins (12). After the age of 24 months, valgus of the knee begins to develop instead (19). Radiographs are indicated if varus is present after this age or is progressive after 1 year, if it is unilateral, if it appears to be severe, or if it occurs in a high-risk group such as heavy black children who walk early (12). Radiographic findings of benign genu varum include bowing of the tibia and femur; a normal-appearing growth plate physis, without narrowing or step-off; and a generalized, rather than focal, varus angle.

Treatment of physiologic genu varum is observation until resolution. On physical examination, the measurement should be performed with the child standing and may also be confirmed by measurement of the distance between the femoral condyles. These methods are not as accurate as radiographs, but they are a practical way of following change in patients when the presumptive diagnosis is physiologic genu varum.

Differential diagnosis of physiologic genu varum includes Blount disease, rickets, posttraumatic growth plate disturbance, enchondromatosis, achondroplasia, or other skeletal dysplasias.

Blount disease (tibia vara) is an idiopathic, mechanical overload of the medial tibial growth plate that may be unilateral or bilateral. It presents initially in two different age groups, childhood and adolescence.

If untreated, infantile tibia vara is almost always progressive; along with the varus, it includes flexion and internal rotation and often increased lateral knee laxity. Radiographs demonstrate progressive depression of the medial metaphysis, growth plate, and epiphysis. Eventually, the medial metaphysis fuses to the epiphysis in severe cases. A helpful early distinction unique to tibia vara is the focal nature of the change (Fig. 105-6), with sharp angulation of the proximal tibial metaphysis, resulting in a metaphyseal-diaphyseal angle of 11 to 16 degrees or more. This is a specific sign because such localized angulation occurs in fewer than 5% of children with physiologic varus, but in essentially all cases of Blount disease (20).

Treatment with a night brace, although not scientifically proven to be effective, is usually used for the mild but definite cases of Blount disease up until about age 3 years. Valgus-rotational osteotomy of the tibia is indicated if the angulation progresses, if growth plate depression occurs, and if the patient is older than 3 years. Recurrence is a risk if treatment begins after 4 years of age, if the epiphysis is fragmented, or if the child is obese. Persistent varus leads to early knee arthritis.

Adolescent tibia vara has onset after 9 years of age. It is to be distinguished from persistent cases of infantile tibia vara. It is most common in obese males. It is believed to be due to decreased growth of the medial tibial physis from excessive medial stresses. Radiographs show medial femoral and tibial bowing. Treatment is osteotomy to realign the limb, or closure of the lateral growth plate to allow catch-up growth medially.

The knee goes through a series of phases of normal alignment. Varus is common before age 2. Valgus of the knee is normal after age 2, reaches a mean of 12 degrees at 3 years, and remains at a mean of approximately 7 degrees in boys and 9 degrees in girls after 8 years of age. If valgus remains over 15 degrees at 10 years, early growth plate stapling or later osteotomy of the affected region may be
indicated to prevent patellofemoral problems and degenerative changes. Valgus of the proximal tibia often develops after medial tibial metaphyseal fractures, but it usually spontaneously corrects at least partially.

The hip develops from a common cartilage anlage resulting from reciprocal contact between the femur and acetabulum during growth. Loss of this contact may occur at any point in development as a result of abnormal in utero positioning; neuromuscular abnormalities such as myelodysplasia, arthrogryposis, and Larsen syndrome; or intrinsic abnormalities in the connective tissue. The earlier this loss of relationship occurs, the more severe are the femoral and acetabular abnormalities; the earlier it is corrected, the more the remodeling potential and the better the potential outcome.

The etiology of dislocation of the hip in an otherwise normal child is multifactorial. Mechanical factors play a role, and the frequency is greatly increased in breech presentation [a factor in 30% of all developmental dysplasia of the hip (DDH)], in firstborn children, and in oligohydramnios. Breech position causes the hip to be hyperflexed and the muscle forces to be increased, causing the femur to be directed out over the edge of the acetabulum. The left hip is slightly more commonly involved than the right. These factors are associated with increased force across the hip, positioning, or both. Hormonal factors may play a role because there is generalized ligamentous laxity around the time of birth due to increased circulating estrogens and relaxin. The incidence of DDH is sixfold greater in girls than in boys. Evidence for hereditary control of these and other factors is that more than 20% of patients have a positive family history.

There are three degrees of hip dysplasia—subluxable, dislocatable, and dislocated hips—in order of increasing severity. In the first type (subluxable), the femoral head rests in the acetabulum and can be partially dislocated by examination. A dislocatable hip is also located normally when at rest, but it can be fully dislocated. A dislocated hip rests in the dislocated position. The combined incidence of these three types is about 1 in 60 births; incidence of a true dislocation is only 1.5 in 1,000. Because of this variability, a change in terminology from congenital dislocation to developmental dysplasia of the hip has become widely accepted. Dysplasia better describes the spectrum of severity, from malformation to dislocation of the hip. Developmental is meant to acknowledge that some cases are not detectable at birth and may occur later; the anatomic findings are continually evolving. The pathologic anatomy includes laxity of the capsulae, which progresses to capsular contraction with time if the hip remains out. The acetabulum becomes shallow because of lack of concentric contact with the femoral head. A false acetabulum may form where the femoral head contacts the lateral wall of the ilium above the normal location. The outer rim of the acetabulum becomes rounded during the period when the femoral head is able to slide in and out of the acetabulum. The movement over this ridge is felt as the “clunk” of the Ortolani and Barlow tests. The proximal femur remains anteriorly rotated (anteverted) as the head rests against the lateral iliac wall.

Physical examination remains the most important means of diagnosis. A general rule is that the signs in the newborn period usually consist of instability without significant fixed deformity, whereas in the later months an untreated dislocation becomes more fixed, and there is less instability and more limitation of certain motions. The Barlow and Ortolani signs should be sought in the newborn (Fig. 105-7). A positive Barlow sign consists of the ability to dislocate the hip; a positive Ortolani sign is the ability to relocate the hip with easy physical manipulation. When performing the tests, the child should be relaxed by keeping him or her warm and on the parent’s lap, and using a pacifier. Only one hip should be examined at a time. The pelvis should be held by one hand of the examiner, whereas the other hand controls the femur with fingers on the greater and lesser trochanters. With adduction
and posteriorly directed pressure, the femur can be felt to slide posterosuperiorly over the deformed acetabulum in the abnormal hip (Barlow sign; Fig. 105-5A) and back in with abduction, causing a dull clunk (Ortolani sign; Fig. 105-5B). Thus these signs, dislocation and relocation, are both aspects of the same condition of hip instability.

Possible errors include examining both hips at once, which impairs proprioception, and mistaking insignificant soft-tissue “clicks” for the more important and palpable “clunk.” These innocent clicks may be due to movement of fascia over the greater trochanter, clicking of the meniscus or the patella, or the stretch of a normal labrum.

Routine screening of neonates since the 1970s has resulted in a dramatic increase in early diagnosis of DDH (21), and thus more successful treatment (22). Approximately 60% of all unstable newborn hips spontaneously become normal within the first 2 to 4 weeks as perinatal laxity resolves. A severely dysplastic hip may have a negative examination due to lack of an acetabular shelf. It is important to stress, however, that not all hips are reducible at birth. This is presumably because of development of dislocation earlier in utero, with evolution of fixed-joint contractures. Similarly, it is believed that a few cases of dysplasia may develop after birth. In most large series, it has been shown that not all abnormal hips can be detected by screening, even by skilled examiners (23). This is because the physical findings are variable and may fall within the range of normal. If the hip remains dislocated, contractures develop, so by the age of about 6 months most cases cannot be relocated on physical examination in the awake patient. Findings of asymmetry, such as limitation of abduction and of full extension, as well as apparent shortening of the thigh, are more sensitive at this time. This last sign, known as the Allis or Galeazzi sign, is noted by comparing the lengths of the two flexed thighs when held together. Asymmetry of skin folds by itself is unreliable and not a highly specific sign, although it is a supportive finding. When the child begins to walk, a positive Trendelenburg sign is noted during gait: When weight is borne on the dislocated side during gait, the pelvis inclines downward, dropping on the other side. Pain is not present, and walking may begin at about the normal age.

The surgeon should be especially alert to the possibility of DDH in children with connective tissue disorders, genetic syndromes, or neuromuscular disease.

Except in teratologic conditions, radiographs are not commonly used before 6 months of age because interpretation is more difficult during this time; physical examination remains more reliable. Many centers are using ultrasonography as an objective tool, but interpretation requires much experience and should be performed by a pediatric radiologist or orthopedist who is familiar with the technique. Ultrasound is indicated for diagnosis if the neonatal examination is abnormal or questionable, as well as to guide initial treatment (22) (Fig. 105-8A and 105-8B). As the infant grows, plain films may more clearly show cephalad and lateral migration of the femur with a break in the Shenton line (Fig. 105-6C), delayed appearance of the femoral ossific nucleus, a shallow and more vertical acetabulum, and, later, formation of a false acetabulum.

Treatment involves different measures at different ages. The aim of these measures is to restore contact between femoral head and acetabulum. Because a high percentage of patients experience spontaneous improvement of lax hip capsules in the early perinatal period, most orthopedists recommend observation of a mild subluxable type of hip, with reexamination at 3 weeks. Dislocated hips are treated at the time of diagnosis. An abduction-flexion device such as a Pavlik harness is most often used. This allows some motion while maintaining the appropriate femoral-acetabular contact. The alignment should be checked by ultrasound or radiography in 1 to 2 weeks (23). The brace is worn until the clinical and radiologic examinations are normal, a duration approximately equal to one to two times the child’s age at diagnosis. If treatment is begun after 6 months of age, the child is usually too large and active to tolerate the brace. Then reduction must be preceded by traction to bring the femoral head down toward the acetabulum, decreasing the muscle forces that could contribute to avascular necrosis. A manipulative (closed) reduction is thus attempted under general anesthetic (24). If closed reduction is not successful, open surgical reduction should be carried out. This involves tightening the lax superior capsule and releasing the tight psoas tendon and inferior capsule, allowing the femoral head to be brought down to its appropriate location.

If there is extensive bony deformation, such as a shallow acetabulum or rotated femur, a femoral or pelvic osteotomy and open reduction might be indicated. This is more common after the age of 2 years.

Possible complications include persistent dysplasia from failure of normal development, redislocation, and avascular necrosis of the femoral head. The last condition is due to impairment of the epiphyseal vessels by excess pressure or capsular stretch. It is the most serious complication. Its occurrence is more likely if the hip is reduced under excessive tension or if excessive abduction is used.

The earlier treatment is carried out, the better is the resultant hip development and the safer each of the steps in treatment. Early detection, when possible, can decrease the need for complex orthopedic procedures later.

Transient (toxic) synovitis of the hip is a diagnosis of exclusion; it is a self-limited condition that is the most common cause of an irritable hip in children. The usual presentation is a painful limp or hip pain of acute or insidious onset, usually occurring unilaterally. The most common ages are 2 to 6 years, but patients from 1 to 15 years have been reported (25). There is moderate spasm on testing of hip range of motion, particularly internal rotation. Temperature, white blood cell count, C-reactive protein, and erythrocyte sedimentation rate may be normal or slightly elevated. The etiology is unknown; an immune mechanism and viral infection have been postulated. Some examples of viral-associated anthropathy have been described. Differential diagnosis should include septic arthritis, osteomyelitis, and Legg-Calvé-Perthes disease, which usually has a subchondral crescent of lucency or further changes in the femoral head on radiograph. Juvenile rheumatoid monarthritis and slipped capital femoral epiphysis should also be considered. Admission to hospital, observation, and early aspiration should be performed if septic arthritis cannot be ruled out. Treatment consists of bed rest with oral analgesics as needed for 2 to 7 days. This can sometimes be performed on an outpatient basis with frequent follow-up if septic arthritis is ruled out. Persistence of symptoms beyond 1 week should prompt the physician to perform reevaluation, although persistence of symptoms for as long as 1 month has occasionally been reported.

Legg-Calvé-Perthes disease was first differentiated from tuberculosis within a decade after clinical use of radiography at the turn of the century, but its etiology is still unknown. This disorder consists of ischemia of the proximal femoral epiphysis (26). The amount of the femoral epiphysis rendered ischemic is variable and affects the outcome. The ischemia is followed by resorption, then reossification with or without collapse of the femoral head. It most commonly affects children 4 to 8 years old, although exceptions are often seen. Males are affected four times as often as females. Affected patients as a group have slightly shorter stature and delayed bone age compared with peers. Fifteen percent of cases are bilateral, although both sides are not usually affected at the same time.

Clinical presentation is usually a limp, such as abductor lurch, with minimal pain of either short or long duration. The pain is not as acute or severe as that of transient synovitis or septic arthritis. Motions that are especially limited are internal rotation and abduction of the hip. Internal rotation is performed with the patient supine, the hip flexed, measuring the angle to which the leg may be rotated laterally. These movements may be resisted by mild spasm or guarding. At the earliest stage, radiographs may be normal or may reveal the slightly smaller size of the affected femoral epiphysis compared with the other side due to its temporary inhibition of growth (27,28). Later, there may be a narrow crescentic lucency, best seen on the lateral view (28), which is due to a microfracture of the bone just underneath the joint surface. This reveals the extent of bone involved. In some cases, revascularization may occur without collapse of the epiphysis, but in others, revascularization of the femoral head is accompanied by progressive resorption and deformation (Fig. 105-9). Reossification follows, and the femoral head continues to grow. Whether this further growth occurs spherically
depends on the patient’s age, the amount of collapse, and the method of treatment.

Differential diagnosis should include transient synovitis, septic arthritis, hematogenous osteomyelitis, sickle cell infarct, hemoglobinopathies, steroid-induced necrosis, Gaucher’s disease, hypothyroidism, and the epiphyseal dysplasias. The last two are often synchronous bilaterally, whereas Legg-Calvé-Perthes is not. Avascular necrosis may also be a serious complication of femoral neck fracture or hip dislocation.

Treatment follows two principles: containment of the femoral head within the acetabulum and maintenance of range of motion. In the early stages of Perthes disease, the avascular portion of the femoral head is less likely to become deformed and more likely to regrow spherically if contained within the mold of the acetabulum by abduction. Children younger than 6 years of age or with involvement of less than one-half of the femoral head may be followed without active treatment if a full range of motion is preserved; patients in this age group have a good prognosis.(26) More aggressive treatment is indicated in patients with involvement of more than one-half of the femoral head or age older than 6 years.