Non-traumatic knee symptoms are common in children and mostly so mild that they do not cause functional impairment.
Clinical examination, good history taking and the investigations available in primary health care are enough to exclude most diseases requiring specialized care.
Other types of arthritis (juvenile rheumatoid arthritis, seronegative arthritis)
Hip or back problems causing knee pain
Fractures from accidents that may go unnoticed in small children particularly
Recurrent limping, systemic symptoms such as fever, or clear objective findings such as limited range of movement and swelling of a joint require further investigations in specialized care.
The hip joint should be carefully examined in every child with knee pain.
Examination of patients with knee pain
Ask the child to undress to their underwear.
Examine the entire back and lower limbs.
Assessment of movement
Walking (limp)
Walking on balls of the feet / heels
Squatting (side-to-side difference when squatting on one leg, either doing a single-leg squat or a lunge)
Posture (scoliosis), back bends
Objective status findings compared with the healthy side
Abnormal range of movement or pain on joint movements (including the hip joint)
Swelling, muscle atrophy
Swollen joint
Medial-lateral or anterior-posterior instability of the knee
Patellar instability
Significant coronal (valgus-varus) malposition, difference in length of lower limbs exceeding 2 cm
Temperature difference, erythema
Abnormal muscle tone
There is a lot of structural variation and variation in how children move (such as mild varus or valgus knee, abnormal valgus posture, inward/outward rotation of feet when walking) in growing children. Such findings rarely have any causal connection with the pain symptoms. However, significant malposition, particularly if unilateral, may be due to a disease that requires treatment.
Further investigations should be done based on clinical findings. The primary radiological examination is plain x-ray.
Osgood-Schlatter disease and Sinding-Larsen disease
Definition
These are repetitive strain injuries involving the patellar ligament and knee extension mechanism (traction apophysitis).
The symptomatic focus of Osgood-Schlatter disease is the tibial tubercle of the lower leg and that of Sinding-Larsen disease the distal pole of the patella.
The disease is common in growing children actively doing physical exercise, particularly running or jumping.
The symptom typically occurs on exertion or thereafter. In difficult cases, the pain may be constant and provoked by even the slightest strain.
Osgood-Schlatter disease typically emerges around the pubertal growth spurt, in boys around the age of 13-15 years, in girls a little earlier.
Sinding-Larsen disease is analogous with ”jumper's knee” (patellar tendinopathy) encountered in adults Treatment and Prevention of Sports Injuries. The symptoms usually begin earlier than in Osgood-Schlatter disease.
Findings
In Osgood-Schlatter disease, the tibial tubercle area may be swollen and painful on palpation. In Sinding-Larsen disease, there are symptoms at the inferior patellar pole.
Examination in the doctor's office may not reveal any objective symptoms and the diagnosis must then be based on patient history.
The diagnosis is based on clinical findings. Imaging can be used as necessary to exclude any other causes of pain. The line of treatment will not depend on any imaging findings suggestive of Osgood-Schlatter disease.
Treatment
Treatment can be carried out in primary health care.
It is essential to explain the cause and the benign nature of the condition to the patient and the parents.
The patient should refrain from exercise that induces pain.
The severity of the symptoms varies so much that it is impossible to give any instructions for how long exactly any individual patient should refrain from sports, for example.
In mild cases, a break of perhaps a couple of weeks from exercise inducing pain can be recommended. The patient should be told that a break is indicated whenever symptoms recur. In case of severe symptoms, partial restriction of physical exercise may be indicated for several months.
It is essential to pause only the physical exercise that causes pain. It should be recommended that such exercise be replaced by swimming, cycling, skiing or skating, for example. Varied physical exercise also lowers the risk of overuse injuries.
As overuse injuries are typically associated with guided physical exercise, a child's normal spontaneous physical activity should be restricted only exceptionally.
A physiotherapist can guide muscle training to improve muscle control in the lower limbs. There are no studies available regarding the benefits of such training.
The disease is not treated surgically in growing children.
Symptoms are often preceded by painful acute dislocation. This may be followed by various degrees of patellar instability with either recurrent dislocation or milder sensations of knee instability and discomfort.
The primary line of treatment of patellar instability is conservative.
A physiotherapist can guide thigh muscle exercises to strengthen the quadriceps muscle and its innermost part (vastus medialis) in particular.
If despite training the patient has recurrent dislocation of the patella or milder sensations of instability causing significant harm, they should be referred to specialized care for assessment of surgical treatment.
Habitual dislocation of the patella means that the patella is dislocated every time the person moves his/her knee (typically when bending the knee). Such cases should be assessed in specialized care in the first place.
Discoid meniscus
Discoid meniscus is a structural variant of the meniscus where (nearly invariably the lateral) meniscus is discoid in structure.
There may be mechanical symptoms (snapping felt in the joint space, restricted extension of the knee) or swelling of the knee.
Symptoms typically begin at the age of about 10-12 years. They may begin gradually, or the meniscus may be injured and the symptoms may begin after knee injury.
In case of clear subjectively disturbing symptoms, referral to specialized care and MRI are indicated.
Suspected discoid meniscus causing mild symptoms can be followed up without more specific imaging.
In most cases, children below the age of about 7 years cannot reliably locate the pain to a certain place in the lower limb.
Even in older children, diseases of the hip area often manifest as knee pain.
The hip joint should be carefully examined in every child with knee pain.
Slipped upper femoral epiphysis (SUFE) in particular may misleadingly produce knee pain. Rapid diagnosis and emergency operative treatment may save the patient from difficult late repair and permanent disability.
Unspecific knee pain in growing children
Anterior knee pain is a common multifactorial symptom in growing children; there is often no single clear cause to be found. The symptoms can be considered equivalent to “patellofemoral pain” in adults. See Patellofemoral Pain (Pfp).
There have been attempts to explain the symptoms by factors such as inadequate muscle control associated with growth in height, tense muscles or, particularly in girls, hormonal changes in puberty also affecting the musculoskeletal system.
More accurate imaging methods and their improved availability (MRI) make it possible to detect milder and milder changes.
Chondromalacia
Folds of the synovial membrane (plica)
Anatomical variation associated with the patellofemoral joint
Any causal relationship between such changes and the pain often remains unclear, and their operative treatment in growing children is basically not indicated.
It is important to inform the patient and the family about the benign and transient nature of the symptoms.
Patients should be encouraged to be physically active and to find types of exercise that do not aggravate or cause pain.
Exercises guided by a physiotherapist may be useful.
References
Slotkin S, Thome A, Ricketts C, et al. Anterior Knee Pain in Children and Adolescents: Overview and Management. J Knee Surg 2018;31(5):392-398 [PubMed]
Wolf M. Knee Pain in Children: Part I: Evaluation. Pediatr Rev 2016;37(1):18-23; quiz 24, 47 [PubMed]
Wolf M. Knee Pain in Children, Part II: Limb- and Life-threatening Conditions, Hip Pathology, and Effusion. Pediatr Rev 2016;37(2):72-6; quiz 77 [PubMed]
Wolf M. Knee Pain in Children, Part III: Stress Injuries, Benign Bone Tumors, Growing Pains. Pediatr Rev 2016;37(3):114-8; quiz 119 [PubMed]