A 13-Year-Old Boy

and Iain McNamara¹

(1)

Trauma & Orthopaedics, Norfolk & Norwich University Hospital, Norwich, United Kingdom

A 13-year-old boy presents to the clinic with gradual onset of left anterior knee pain, particularly associated with sport, worsening over the previous 6 months. He is otherwise fit and well and plays football. It does not really limit what he does, but it does ache afterwards.

On examination the only abnormal finding was a lateral-to-medial movement of the patella at 20° of flexion.

It was felt that some VMO strengthening exercises would improve his symptoms. He was referred to physiotherapy.

Question 1

What is the most likely diagnosis?

Question 2

What is its natural history?

Question 3

What in the history and examination would suggest further investigations should be requested?

Question 4

What diagnoses should be considered and what further investigations specific for each?

At the age of 15 years old, he was admitted via the Emergency Department following a twisting injury to his left knee playing soccer. He had immediate swelling and was unable to weight-bear on the leg.

Question 5

What is the most likely diagnosis?

Examination on the ward found that his knee was swollen. He could flex the knee comfortably to 45⁰ but was unable to extend actively because of discomfort. Palpating the extensor mechanism showed that it was intact. He had “some” tenderness on the anterior part of the medial tibiofemoral joint line. He was tender over the medial retinacular ligament. The ACL was noted to be normal.

Question 6

What is the diagnosis or differential diagnosis?

Question 7

What would you expect to see on the plain X-ray of the knee?

He was mobilised in a knee orthosis locked in extension, outpatient physiotherapy organised and a clinic appointment for 12 days later arranged.

Examination at that time was recorded as “he has no tenderness over the medial patellar retinaculum or the medial facet of the patella but tenderness over the lateral border and medial joint line. He was able to straight leg raise and his collaterals were not lax; his ACL, however, did seem to be more lax than the other side and he has 0–90⁰ of flexion”.

Question 8

What other examination findings should be recorded?

His plain radiographs were reviewed and showed “a possible osteochondral fragment, but this may well be old and particularly given the fact that he was non-tender in the medial patellar facet today. I wonder whether he has an ACL injury”. The notes also commented, “He is not particularly lax with a low Beighton score, but his trochlear groove is quite shallow”.

The management plan then was to unlock the orthosis, continue physiotherapy, book an MRI scan, and review in 5 weeks.

Question 9

What findings on the MRI scan would support a diagnosis of an ACL rupture?

Question 10

What would you look for on the MRI scan if the trochlear groove is shallow?

Following his MRI scan, he was referred to the Patella Clinic where he was seen 4 months after injury. At that stage, he reported recurrent instability of the knee from the age of 11 years old with the most recent episode being the soccer injury 4 months previously. He had had gradual improvement, but his knee that still had not settled down still became swollen and was uncomfortable. He had tried to return to sports but was not fully back. He still awaited physiotherapy. There was no significant family history. His Kujala score was 81.

Question 11

What would you look for on examination?

The examination findings showed that the Beighton score was 0. He had a mild femoral anteversion with internal tibial torsion. He had no patellar apprehension, slight J-shape tracking of the patellae. There is a firm end point with an ML glide of the patella in full extension of 2+, slightly less than on the right knee. There was a full range of knee movements.

Question 12:

(a)

What is the Beighton score and how is it assessed?
(b)

How is the rotational profile assessed clinically?
(c)

How is patellar apprehension measured?
(d)

How is patellar tracking recorded?
(e)

How is the mediolateral glide assessed and recorded?
(f)

What other tests for patellofemoral instability are there?
(g)

What is the evidence for the validity of these tests?

The plain radiographs taken at the time of injury are shown below:

Question 13

Describe the findings on the plain radiograph and from these what is the diagnosis?

The MRI scan is shown below:

Question 14

(a)

What is the MRI sequence?
(b)

What is shown?
(c)

What is the diagnosis?

Question 15

How would you now manage him?

He returned to the Patella Clinic 7 months after his injury with a further episode of patellar instability. He had felt the patella go out of joint, but it had relocated spontaneously. He and his parents were keen for an operative solution.

Question 16

(a)

What information do you need to decide on the appropriate procedure?
(b)

What operations should be considered?
(c)

How do you select the appropriate operation?

He was admitted for an operation 2 months later and underwent a medial patellofemoral ligament reconstruction under general anaesthetic.

Question 17

(a)

What is the anatomical femoral tunnel position?
(b)

What needs to be considered about the femoral tunnel position in this case?

His post-operative plain radiographs are shown below:

Question 18

(a)

What can you say about the technique used for the MPFL reconstruction?
(b)

Why has the femoral tunnel been positioned away from the anatomical one?

Question 19

(a)

How is an MPFL reconstruction managed post-operatively?
(b)

What is the evidence base for this approach?

He was reviewed in the clinic 6 weeks later and was noted that he was much improved. He had regained his quadriceps control and full knee extension. He had lost about 15° of flexion and needed to work on that. He was advised to exercise on a wobble board and return to all activities as comfort and confidence allows. It was planned to review him 1 year from operation.

Question 20

Why progress to using a wobble board?

Interestingly 6 months later, he was referred to the Fracture Clinic having sustained a dislocation of his right patella. He was noted to have had a good result from an MPFL reconstruction but had dislocated his right patella which was previously asymptomatic. He did this going down the stairs. Aggressive physiotherapy was organised and an MRI scan booked. He was to be reviewed after this.

Answers

Question 1

What is the most likely diagnosis?

Adolescent anterior knee pain

Question 2

What is its natural history?

In a survey of school children, 30 % of both boys and girls from 12 to 18 years old developed adolescent anterior knee pain. Of these a tenth of the boys and a third of the girls presented to primary care with the problem. The only factor that correlated with the symptoms was playing sports. The natural history is that the symptoms settle after the end of the growth spurt soon after physeal closure.

Fairbank JCT, Pynsent PB, Van Poortvliet JA, Phillips H. Mechanical factors in the incidence of knee pain in adolescents and young adults. J Bone Joint Surg [Br] 1984; 66-B: 685–692.

Question 3

What in the history and examination would suggest further investigations should be requested?

In secondary care, the typical history is a girl about 14 years old with bilateral anterior knee pain associated with playing sports. The pain settles with rest and does not keep them awake. The knee is dry. The type and amount of sports are adjusted to keep the level of pain that can be tolerated. Patients who have had trauma to the knee need further investigation. It follows that if the pain is not exercise related, persists throughout the day and keeps them awake, it requires further investigation; likewise if the symptoms continue after the end of growth. Unilateral symptoms mean careful comparison of both limbs is needed.

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