A 14 year old male
presented with anterior left knee pain of 2 weeks duration with no history of
trauma. The knee pain was aggravated by exercise and relieved by rest. On
physical examination, there was focal tenderness at the left tibial tuberosity
and the pain was reproducible on forced extension of the knee. The rest of the
knee examination did not reveal any joint instability. A radiograph of the knee
was performed (see Fig. 1). What does the image show and what is the diagnosis?
As his pain persisted, a MRI of the knee was subsequently performed (see Fig.
2). What do the images show?

Image
interpretation

Knee X-ray: There is
bony irregularity with fragmentation at the tibial tubercle. A small well
corticated bony fragment is noted superior to the tibial tuberosity (see arrow
in Fig. 1a). There is mild soft tissue swelling at the expected patellar tendon
insertion site. There is however, no
significant joint effusion.

MRI Knee: There is a
small ossicle in the distal pre-insertional part of the left patellar tendon
which shows well-defined corticated margins and no identifiable marrow oedema
(see Fig. 1b). The adjacent left tibial tuberosity shows mild marrow oedema
just deep to the articulation with the ossicle (see Fig. 1cb). The rest of the
patellar tendon shows normal thickness and signal characteristics.

Diagnosis

Osgood-Schlatter
disease (OSD)

Clinical
course

He was treated
conservatively with administration of a short course of oral analgesics along
with rest and modification of exercise. The symptoms subsequently resolved with
no further functional impairment or pain.

Discussion

Osgood-Schlatter
disease (OSD) is a traction osteochondritis
involving the tibial tubercle, first described in 1903 separately within the
same year by Dr Robert Osgood and Carl Schlatter 1,2. It is characterized
clinically by the presence of pain and swelling of the tibial tuberosity in the
adolescent patient 3.

It is widely accepted
as a traction apophysitis involving the tibial tubercle and the distal aspect
of the patellar tendon. There is chronic and repetitive injury to the distal
patellar tendon and avulsions of the cartilaginous attachment of the patellar
tendon to the secondary ossification centre of the tibial tubercle. Foci of
heterotopic ossification may occur
when the avulsed cartilage fragments ossify. 3

Incidence
and epidemiology: Typically, it occurs
in the adolescent due to recurrent avulsion and microtrauma of the developing
tibial tuberosity. It occurs more commonly in males from ages 12to 15 and
earlier for females at ages 8 to 12, due to the earlier onset of the pubertal
growth spurt, and may manifest bilaterally in 20-30% of the patients 4.
Higher incidences of OSD are observed in those who are active in sport compared
to those who are inactive, 21% vs. 4.5%, respectively 3.

A review of 794
published cases in the literature revealed that 72% of all cases of OSD are
males 5. The male predominance has been attributed to the greater
participation in sports and faster skeletal growth in the male adolescent.

 

 

Clinical
presentation:  Patients with
OSD usually present with pain over the anterior aspect of the knee and
tenderness with application of pressure on the tibial tubercle.  Any activity requiring contraction of the
quadriceps mechanism aggravates the pain which improves by rest. There may be
enlargement of the tibial tuberosity, thickening of the patellar tendon or
joint swelling. On physical examination, tenderness is elicited on palpation or
application of pressure on the tibial tubercle and patellar tendon. As in our
patient, pain is reproducible by resisted active extension of the knee 3.

Investigations:
The diagnosis of OSD is based on
clinical examination, with additional radiographic investigations to exclude
fractures or bony tumours. 3

Radiological findings/modalities:
Plain radiographs of the knee may demonstrate fragmentation, increased density,
irregularity or enlargement of the tibial tubercle (see fig 3).

On
MRI imaging, the normal patellar tendon should be homogeneously low signal on
T1, T2 and proton density weighted images. The normal thickness of the patellar
tendon increases proximally to distally, but should not exceed 7 mm in
thickness 6. The presence of either
focal or diffuse thickening and/or presence of intermediate T1W and T2W signal
may represent pathology 7.

Sagittal MR images in
OSD may reveal enlargement of the distal aspects of the patellar tendon, low
signal intensity foci of heterotopic ossification and irregularity or
enlargement of the tibial tuberosity. Distention of the deep infrapatellar
bursa may be due to the presence of fluid between the deep surface of the
patellar tendon and anterior cortex of the tibia. There may be increased signal
on T2W images demonstrating oedema at the tibial tuberosity and tibial
epiphysis. 4, 6 (see Fig. 4)

Ultrasonography
may also demonstrate abnormalities surrounding the patellar tendon attachment
such as reactive bursitis, patellar tendon lesions, cartilage swelling and
neovascularisation at the tibial tuberosity. 8

Treatment:
Conservative measures by local application of ice packs and oral administration
of analgesia comprise the mainstay of therapy. Modification of exercise is
suggested with avoidance of strenuous activities. Strengthening and stretching
exercises may help. Protective pads which are worn over the tibial tubercle may
help avoid direct trauma to the tibia tubercle, although cast immobilization is
not advised as wasting of the quadriceps muscle may occur. Surgical management
may be considered in patients where conservative measures have failed and after
fusion of the tibial growth plate 3. Rarely, surgical management is required
for unresolved OSD.
In cases where there are persistent symptoms after skeletal maturity, surgical
treatment may be advocated with good outcome and without long term deleterious
effects 9. One of the studies showed promising results for hyperosmolar
dextrose injection together with lidocaine over the apophysis and patellar
tendon origin with subsequent improvement of symptoms, although more research
is needed before routine recommendation of this procedure can be recommended 10.
In general, OSD tends to be self-limiting with resolution of symptoms in more
than 90% of patients, and good overall prognosis with non-operative treatment.