Knee problems in children are encountered regularly by primary care physicians.
It is important to carry out a thorough clinical examination. Referred pain from a back or hip disease should be excluded during the examination. The need for further investigations depends on the degree of clinical signs present.
Most knee problems in growing children - often vaguely associated with exercise or physical activity - are so mild that they do not cause functional impairment. However, a significant mechanical defect, an overuse injury or arthritis may be suspected if the pain makes the patient limp continuously or limits sports activities, or if the patient describes mechanical locking of the knee or, for example, dislocation of the patella.
The affected knee should be compared with the contralateral knee. Positive clinical signs include the following: limited range of motion, instability, effusion, synovial swelling, other swelling or deformity, differences in temperature (heat or coolness), atrophy of thigh muscles, local tenderness in sites typical of overuse injuries, asymmetrical tenderness during patellofemoral compression, continuous limping and a side-to-side difference when squatting on one leg.
It is common for the child and the accompanying adult to assume that the current knee problem is associated with a structural abnormality of the foot or knee. The observations of the accompanying adult should be taken seriously even though a causal relationship between a structural variation and knee pain is extremely rare.
This term, together with ”anterior knee pain”, has been used loosely to describe unspecified and indeterminate anterior knee pain in adolescents and adults.
Chondromalacia literally refers to damage, softening or cracking of the patellar cartilage, or its detachment from the bony surface, which can be verified with arthroscopy or an MRI scan.
In fact, the condition is an osteoarthritic change caused, for example, by trauma, recurrent partial or complete dislocation of the patella, prolonged inflammation, repeated bleeds or patellar osteochondritis dissecans.
Symptoms
Symptoms are similar to those seen in patellofemoral osteoarthritis: anterior knee pain on weight bearing felt during heel strike and/or when the patient pushes with the affected leg when, for example, running or climbing or descending stairs.
The ”cinema sign” is typical: the patient experiences knee pain, and a desire to straighten the knee, when sitting for prolonged periods with the knee flexed during car journeys or visits to the cinema.
Clinical signs
Muscular atrophy develops quickly in the anterior thigh.
Resisted knee extension with the patient sitting, for example, on the edge of a bed produces pain at a specific angle between 90 and 20 degrees of flexion, as does squatting with one leg.
Crepitus may be heard and felt.
In some cases, chondromalacia is associated with clinically observable patellofemoral joint instability.
Treatment
If the patient has objectively established arthritis of the patellar cartilage, no curative treatment is available.
The symptoms are usually intermittent, and even a considerable cartilage defect may become asymptomatic over time.
Restraint should be exercised as regards invasive treatments in children, such as injections and arthroscopic smoothing of the cartilage.
The first-line treatment should consist of a sufficiently long monitoring period or an attempt to treat the condition with muscle exercises, NSAIDs and possibly by strapping carried out by a physiotherapist.
Osgood-Schlatter disease and Sinding-Larsen disease
Definition
These are repetitive strain injuries involving the patellar ligament attachment sites and knee extension mechanism. 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.
Osgood-Schlatter disease is encountered frequently. The patient is usually a young athlete, who may even participate in competitive sports. The symptoms emerge around the pubertal growth spurt, in boys around the age of 13-15 years, in girls a little earlier. An ambitious training programme is often behind symptoms that emerge before the growth spurt.
Sinding-Larsen disease is analogous with ”jumper's knee” (patellar tendinopathy) encountered in adults Treatment and Prevention of Sports Injuries. Typically, the afflicted patient is around 10 years of age, sometimes younger.
Symptoms
Running and jumping will produce focal pain in the upper part of the lower leg or the anterior knee.
When running the pain is more intense at the moment of heel touch than at take-off (physiology of the knee extensor apparatus and muscles!).
Clinical signs
In Osgood-Schlatter disease, the tibial tubercle is prominent and painful on palpation and percussion. In an acute phase, the skin over the tubercle feels hot to touch.
In Sinding-Larsen disease, the distal pole of the patella is painful when pressed. The pain is most easily elicited by first making the patient relax the front thigh muscles and the patellar ligament as ligament tone will mask any tenderness on palpation.
An x-ray will show a tibial tubercle or a fragmented distal pole of the patella. In a typical case, an x-ray is not necessary.
Treatment
Treatment can be carried out in primary health care. The condition must be explained to the patient and the parents.
The patient should refrain from exercise that induces pain (exemption from sports involving running or jumping for 3 months at a time).
Recommended exercises during the prohibition of running and jumping include swimming, cycling, skiing, skating or weight training in a gym.
Commercially available jumper's knee supports may also relieve symptoms.
Running should not be allowed until percussion tenderness on the tubercle has completely subsided.
In very mild cases the child may be allowed to continue with physical exercise as tolerated and according to symptoms, but this may lead to the symptoms persisting for several years, until growth has been completed.
If the symptoms are very severe, the treatment options include immobilisation in a plaster cast for 4-6 weeks and the excision of a very prominent tibial tubercle and/or the intratendinous loose body after growth has ceased.
Intra-articular folds (plicae) of the synovial membrane are normal structures and are encountered in almost all people, including asymptomatic people. This diagnosis is often reached when persistent, unspecified knee pain warrants arthroscopy. If the only finding during the arthroscopy is a synovial fold it is usually removed in the hope that the patient's symptoms would improve.
In some cases the symptoms improve, in others not. The clinical relevance of this diagnosis is therefore controversial. It has been assumed that a fold may scar or thicken as a result of trauma or overuse, and these indications have been cited postoperatively when justifying the surgical intervention.
There must be good grounds to carry out knee arthroscopy in a child since the procedure must be carried out under general anaesthesia, and it is unlikely that an untreated fold would lead to significant permanent damage. If the assumed fold causes clinical signs, e.g. limping, limited range of movement or muscle atrophy, the procedure is warranted after an MRI scan.
Unspecified knee pain in an adolescent
A very common reason for seeking medical attention, especially in girls at the end of their growing period.
Symptoms are associated with the growth spurt. The condition is referred to as ”adolescent growing pains” and will improve spontaneously within weeks to months.
Other diagnoses can with sufficient certainty be excluded in the initial assessment if there are no objective clinical findings and if the native x-ray is normal.
The pain is nonspecific and the episodes of pain last from a few seconds to several hours. The symptoms are often not related to exercise or are vaguely associated with school sports or other physical activity.
Diagnosis
When taking the history it is important to ascertain how great a problem the pain is in reality.
A careful clinical examination and a plain x-ray
The absence of thigh muscle atrophy supports the diagnosis.
If other clinical signs are also absent, there is no need to proceed with further investigations.
Treatment
Over diagnosis and excessive treatment should be avoided.
If there are no clinical signs, there is no need to proceed with MRI scanning, knee arthroscopy or experimental treatments, such as physiotherapy or shoe inserts.