Knee pain in children and adolescents is one of the most prevalent complaints in a pediatric practice, accounting for at least a third of musculoskeletal complaints. Accurate diagnosis requires an understanding of knee anatomy and patterns of knee injuries and skill in physical examination. This review covers the most common causes of knee pain in children and adolescents, including overuse issues, such as Osgood-Schlatter and osteochondritis dissecans, as well as traumatic injuries, including tibial spine fractures and anterior cruciate ligament injuries.
Key points
- •
A patient’s description of knee pain is helpful in focusing the differential diagnosis.
- •
A good history and physical examination, followed by appropriate imaging is paramount for the diagnosis. Always check and examine the hip joint as well.
- •
A history of locking episodes could suggest meniscal injury or plica.
- •
A sensation of popping at the time of injury suggests a ligamentous injury. Giving way of the knee may represent ligamentous injury, patellar subluxation or dislocation, or even quadriceps inhibition or malfunction.
Introduction
Knee pain is one of the most common musculoskeletal complaints seen in the pediatric and adolescent population. The complaint is most prevalent in physical active patients, with up to 54% of athletes having some degree of knee pain per year. The knee is a trocho-ginglymus joint allowing flexion and extension as well as slight internal and external rotation. The 2 joints within the knee consist of the patellofemoral articulation between the patella and femur and the tibiofemoral joint between the tibia and femur. A fairly extensive differential diagnosis exists for knee pain and can present a challenge to physicians. A detailed history, focused physical examination, and, when indicated, appropriate use of imaging modalities and laboratory tests can lead to accurate diagnosis and treatment.
Assessment
A patient’s description of knee pain is helpful in focusing the differential diagnosis. As with any patient evaluation, a history of the pain must be elicited and should include the characteristics of the pain, onset (acute or insidious), location, duration, severity, quality, and radiation. Aggravating or alleviating factors should be identified, and if the knee pain was caused by acute injury, the ability to weight bear after the injury should be discerned. Mechanical symptoms, such as locking, popping, catching, or giving way of the knee, should be ascertained. A history of locking episodes could suggest meniscal injury or plica. A sensation of popping at the time of injury suggests a ligamentous injury. Giving way of the knee may represent ligamentous injury, patellar subluxation or dislocation, or even quadriceps inhibition or malfunction. A history of prior knee injury or surgery is important, as is a history of rheumatologic disease.
The presence of an effusion is important to note for knee pain. Rapid onset of effusion after an acute injury suggests a hemarthrosis and could represent fracture or cruciate ligament injury. A slow onset of effusion may represent meniscal injury or ligament sprain. An effusion in the absence of injury may indicate infection. If an acute injury occurred, the patient should be questioned about the specific mechanism of injury. It is important to determine if there was a direct blow, the direction of the blow, if the foot was planted at the time of injury, if the patient was accelerating or decelerating, a twisting component, or if landing from a jump. An anterior blow to the tibia with the knee in flexion can cause posterior cruciate ligament (PCL) injury. A valgus force produces a medial collateral ligament (MCL) injury whereas a varus force produces a lateral collateral ligament (LCL) injury. The anterior cruciate ligament (ACL) can be ruptured with a deceleration, hyperextension, and rotational injury. A rotational injury can also cause meniscal damage or patella subluxation. Any of these forces in children could produce fractures other than ligamentous injury due to the relative strength of the ligament compared with bone in this age group.
Physical Examination
The physician begins the examination of the knee by starting at the more proximal joint, the hip. Pain from the hip can be perceived as knee pain, likely due to the innervation of the anterior branch of the obturator nerve or articular branches of the femoral, common peroneal, or saphenous nerves. It is, therefore, mandatory that a complete examination of the hip accompany an examination of the knee. The knee evaluation is conducted by comparing the asymptomatic knee to the painful one. The injured knee is inspected for erythema, bruising, swelling, and discoloration. The musculature around the knee should be symmetric on both sides, and, in particular, the vastus medialis obilquus should be noted for any signs of atrophy.
The knee is then palpated, and areas of tenderness should be noted, particularly at the tibial tubercle, patella, joint line, and femoral condyle in flexion. The patella should be checked to see if it is ballotable, indicating effusion of the joint, and any warmth of the knee noted. Range of motion should be examined by flexing and extending the knee as far as possible. During the range-of-motion examination, patellofemoral tracking should be noted and the presence of crepitus detected. The Q-angle can be determined by drawing a line from the anterior superior iliac crest through the center of the patella and a second line from the center of the patella to the tibial tuberosity. A Q-angle greater than 15° may be a predisposing factor for patella maltracking. A J-sign is noted, which is the movement of the patella laterally on terminal extension of the knee. Patella mobility can be assessed both laterally and medially, in which one quadrant of motion is considered normal, and a patellar apprehension test can be performed. With a laterally directed force on the medial aspect of the patella, the physician attempts to subluxate the patella from 0° to 90°. If this reproduces a patient’s pain or feeling of giving way, this test is positive.
Assessment of the cruciate ligaments begins with the knee flexed at 90° ( Table 1 ). Normally, the medial tibial plateau extends 1 cm anteriorly beyond the femoral condyle when the knee is flexed to 90°. Posterior displacement of the tibia indicates a torn PCL. Next, the examiner sits on the foot and positions a hand behind the proximal tibia with the thumbs on the tibial plateau. A posterior directed force assesses for the posterior displacement of the tibia; increased posterior displacement compared with the contralateral side is indicative of a partial or complete tear of the PCL. An anterior drawer test can also performed, which can compare anterior displacement of the tibia with the uninjured side. Increased anterior displacement suggests ACL disruption. Chronic injuries tend to be more sensitive to the anterior drawer test than acute injuries. In general, the Lachman and pivot shift tests are both more sensitive and specific to ACL injuries and are the preferred tests to the anterior drawer. The Lachman test is performed with a patient in the supine position and the knee flexed to 30°. The examiner stabilizes the distal femur with one hand and the proximal tibia with the other. The tibia is then attempted to be subluxated anteriorly; lack of a clear endpoint to translation or increased translation compared with the uninjured side is indicative of a positive test.
The collateral ligaments are tested with a patient’s leg in slight adduction. The examiner places one hand on the lateral aspect of the knee joint and the other hand on the medial aspect of the proximal tibia. Valgus stress is applied at the knee at both full extension and at 30°. Laxity of the tibia or absence of an endpoint on examination indicates disruption of the MCL at 30°; at full extension, it indicates disruption of the MCL and one of the cruciate ligaments. Varus stress testing is similar to valgus stress testing except the examiner’s one hand is placed on the medial aspect of the knee joint and the other hand on the lateral aspect of the proximal fibula.
Patients with injury to the meniscus usually demonstrate tenderness at the medial or lateral joint line. Flexion of the knee enhances the palpation of the anterior portion of both menisci. The McMurray test as originally described involves the patient supine with the knee fully flexed. With the knee in flexion, the tibia is rotated internally to test for the posterior horn of the lateral meniscus and externally rotated to test for the medial meniscus. An appreciable snap is considered positive and indicative of a torn meniscus. By altering the position of flexion, the whole of the posterior segment of meniscus can be examined (see Table 1 ).
Protocols have been developed to try to reduce the number of radiographs used in the evaluation of extremity injuries. The two best-known guidelines are the Ottawa knee rules and the Pittsburgh rules. In a prospective study, the Pittsburgh rules were more specific and sensitive than the Ottawa rules. If using the Pittsburgh rules, the inability to bear weight, effusion, or ecchymosis is an indication to obtain anteroposterior, sunrise, and lateral radiographs of the knee ( Box 1 ). In patients with chronic knee pain and recurrent effusions, a notch or tunnel view (posteroanterior view of the knee flexed to 40°–50°) should be obtained. Clinical judgment should always be used, however, for the determination if radiographs are necessary. If radiographs are inconclusive, advanced imaging, such as MRI, may be necessary.
Full access? Get Clinical Tree
