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Knees in children and adolescents

The knee is the largest joint in the human body, extremely complex in structure, and therefore prone to various diseases and injuries. Children primarily experience height growth “from the knees,” and due to the increasing and more intense involvement in sports at an early age, knee issues in children and adolescents are one of the common reasons for visits to pediatric orthopedists. Children often attribute knee pain to rapid growth, and parents frequently share in the clinic that they had similar knee problems as children, requiring exercises.

The knee joint consists of three bones:

• the lower part of the femur (thigh bone)
• the upper part of the tibia (shin bone)
• the patella (kneecap).

To improve the congruence (matching) of bones in the knee, crescent-shaped cartilaginous structures called menisci are located between the femur and tibia. Numerous ligaments in and around the knee, along with tendons and muscles, contribute to the knee’s stability, ensuring a full range of motion. Each of these knee components can be a source of issues in children and, therefore, a reason for a visit to a pediatric orthopedic surgeon.

Examination of the knee in children and adolescents

Every examination begins with a conversation with the child and their parent or legal guardian to identify the reason for the visit. If pain is involved, it is essential to determine when it started, how long it has been present, whether it worsens with activity, and if there have been any injuries or specific moments triggering knee pain. Children often do not recall traumatic events, and the pain may gradually appear. The nature of the pain is crucial – severe, limiting pain differs from evening discomfort or nighttime pain. Checking for swelling or changes in skin color around the knee is important. Understanding whether there is pain and restricted mobility in the knee, indicating a possible meniscus injury, is crucial. Attention should be given to feelings of knee instability, which may signify a torn anterior cruciate ligament (ACL) or patellar instability.

Continuing the examination, an inspection of the child’s knee is performed. The child should be in their underwear for a full view of the leg. Observations include assessing leg axes, whether there is pronounced valgus (knock knee, “X” shape) or varus (bow knee, “O” shape) alignment, or if the knee is slightly bent and cannot be fully extended. Contours of the knee, patella position, swelling, thickening, or changes in skin color are examined. Hypotrophy of the thigh muscles is a sign of weakness or chronic knee pain and should be noted. Finally, observing the child’s gait, checking for any signs of limping, finalize this part of the examination.

Following the standing examination, the child lies down for palpation, where specific areas of tenderness in the knee are assessed through touch. Sometimes, it’s helpful to have the child point to the most painful spot. Palpation includes checking the patella – assessing its stability, ends of the femur and tibia, joint line, and the posterior (popliteal) part of the knee. Patellar tip tenderness indicates Sinding–Larsen–Johansson disease, while tenderness of the tibial tuberosity (bony bump under the knee cap) suggests Osgood–Schlatter disease. If a child experiences pain during palpation of the femoral ends in the knee, with a feeling that something is skipping in the joint, the cause may be osteochondritis dissecans. Palpation also helps identify the presence of joint effusion, which may indicate bleeding following meniscus injury, anterior cruciate ligament injury, or patellar dislocation. Effusion in the knee without a previous injury may signal transient synovitis, juvenile idiopathic arthritis, or septic arthritis.

Next, specific tests for ligamentous stability of the knee are conducted to assess the condition of the anterior and posterior cruciate ligaments, medial and lateral collateral ligaments, and ligaments associated with the patella. The condition of the meniscus is evaluated using compression and rotation tests in various positions. The range of motion in a child’s knee is from fully extended to approximately 150º when the knee is bent. Some children may have more lax ligaments, allowing them to extend the knee 5-10º more than straight. During this part of the examination, it’s also checked whether there is any shortening of the thigh muscles, which can occur in children during periods of rapid growth. Finally, during every knee clinical examination, an assessment of the range of motion in the hip is conducted, as children may perceive hip issues as knee pain.

After the clinical knee examination, if there is a need for clarification of issues or confirmation of certain suspicions, knee imaging is required. An ultrasound of the knee can be performed immediately in the clinic to confirm the presence of effusion, the existence of a popliteal cyst, or assess the condition of ligaments around the knee. Knee bones should be visualized through X-ray imaging, at least in two projections: anteroposterior (AP; front view) and lateral (LL; side view). When there is suspicion of patellar issues, an axial patellar view should also be taken. In the case of pronounced “X” or “O” leg shapes, panoramic X-ray images of the lower extremities are needed, taken while standing, to assess anatomical and mechanical leg axes. However, the knee comprises many ligamentous, tendinous, and cartilaginous structures not visible on X-ray images. Therefore, for insight into their condition, an MRI is necessary, for instance, to evaluate meniscus, cartilage, or cruciate ligament injuries.

While visiting a pediatric orthopedist, it’s crucial to approach the problem from a medical context. However, the social and psychological significance of the occurrence and development of knee disorders in a child should not be neglected. For example, a child with an unstable knee may not feel comfortable playing, avoid socializing due to fear of new injuries, and ultimately withdraw and suffer. Therefore, timely intervention and bringing the child for an examination are essential to prevent further negative consequences from all possible aspects.