When children complain about pain in the knee, obtaining a detailed history is necessary. The complaints are often diffuse, and it is difficult to determine whether the source of pain is the knee itself or the hip. Pain at rest must be differentiated from pain with activity and from pain after activity.
Typical knee problems in children are as follows.
Osgood-Schlatter Disease and Sinding-Larsen-Johansson Syndrome
Both Osgood-Schlatter disease and Sinding-Larsen-Johansson syndrome are typical overuse syndromes that occur in highly active children, usually ages 10 to 14 years. The reason is apophysitis (irritation and partial collapse of the growth plate) on the respective end of the patella tendon. The muscles straightening the knee are strong, and those forces are transferred to the tibia (shin bone) over the patella (kneecap) and the patellar tendon (tendon between the kneecap and the shin bone).
Osgood-Schlatter disease affects the tendon insertion at the tibia (shin bone), and Sinding-Larsen-Johansson syndrome affects the tendon insertion on the lower tip of the patella (kneecap).
Pain usually starts during sports or in early stages after sports. The pain is activity-related, and children often complain when climbing stairs. In most cases, the pain can be well localized. Diagnosis is based on physical examination and tender points.
Rest and a cool pack or ice pack can help to eliminate pain. Physical therapy, stretching exercises, and activity modification are recommended to minimize symptoms. Symptoms almost always stop at the end of growth, but they can be persistent until then, especially when sports activities are continued.
Jumper’s knee (patellar tendonitis) must be differentiated from Osgood-Schlatter disease and Sinding-Larsen-Johansson syndrome. With Jumper’s knee, the patellar tendon itself is inflamed or injured from overuse. Pain is typically localized at the tendon below the kneecap. This disorder can also be found in adults.
Many of these overuse syndromes can be prevented by a good warm-up regimen that includes stretching and by stretching after exercise.
Osteochondritis Dissecans
Osteochondritis dissecans is most likely caused by repetitive microtrauma and decreased bone blood supply. The subchondral bone is affected and separates the cartilage from the rest of the bone. As a result, the cartilage can get partially or completely separated and the fragment can detach and form a loose body within the joint. Pain can be mild and nonspecific and is usually related to activity. The area mostly affected is the medial (inner) part of the femur (thigh bone).
Early-stage lesions in young children can heal spontaneously with rest and activity modification. In more advanced stages, arthroscopy and drilling through the subchondral bone lamina can increase the healing rate. In cases with partial detachment, refixation with self-absorbing pins can be necessary. When the cartilage has detached completely, the lesion needs to be stabilized and covered with synthetic tissue or cultivated cartilage tissue.
Axial Malalignment and Torsional Malalignment
Axial malalignment (bowlegs and knock-knees) or torsional (rotational) problems (in-toeing or out-toeing) of the lower limbs are common abnormalities that can easily be detected by observing the gait pattern. If the malalignments are symmetrical, they are usually idiopathic deformities (of no specific cause). Malunited (incorrectly healed) fractures and injuries with which the growth plate has been damaged can also lead to axial and/or torsional malalignment.
Patella-Femoral Dislocations and Ligament and Meniscal Injuries
The patella (kneecap) sits in the trochlear groove of the femur (thigh bone) and is fixed on the sides with ligaments. If the kneecap leaves the groove, we speak of a patella dislocation.
Patella dislocation can occur with trauma, sometimes in the presence of predisposing factors. If the predisposing factors are substantial, the patella can dislocate with minimal trauma or “habitually” on its own without any traumatic event.
In cases of first-time traumatic dislocations, physical therapy is often enough to provide correction. In other cases, especially in cases of repeated dislocation, soft tissue surgery with reconstruction of the ligament that stabilizes the patella (medial patellofemoral ligament [MPFL] reconstruction) or displacement of tendons might be necessary to enable a central and stable position of the patella. In certain cases, predisposing factors, such as knock-knees, torsional malalignment, or a shallow trochlear groove, must also be addressed. Fortunately, damage to the meniscus or cruciate ligaments is exceedingly rare in children. However, such injury patterns can be found in professional and semi-professional young athletes and require age-appropriate treatment taking into account residual growth.