CASE REPORTRadiographic Abnormalities of the Inferior Pole of the Patellain Juvenile Athletes
Jun Iwamoto,1 Tsuyoshi Takeda,1 Yoshihiro Sato2 and Hideo Matsumoto1

Institute for Integrated Sports Medicine, Keio University School of Medicine, Tokyo, Japan2
Department of Neurology, Mitate Hospital, Fukuoka, Japan

1(Received for publication on April 28, 2008)(Revised for publication on June 23, 2008)(Accepted for publication on July 17, 2008)

Abstract
We examined radiographs of the inferior pole of the patella in seven juvenile athletes diagnosed as having Sinding-Larsen-Johansson disease (SLJD) and discussed the etiology of the
syndrome. Eight knees had tenderness at the inferior pole of the patella accompanied by radiographic abnormalities. A regular or irregular calcification was found at the inferior poleof the patella in three knees; coalescence of the calcification was found in two knees; incorporation of the calcification into the patella to yield a normal radiographic configuration of
the area was found in two knees; and a small calcification separated from the patella wasfound in one knee. All of these findings varied and did not always correspond to the radiographic stages of the disease process identified by Medlar. One case was not clearly distinguished from either osteochondritis or stress fracture, and one case had a similar symptom
to tendinitis. Thus, the etiology of the syndrome seems not to be unified, and the differential
diagnosis between SLJD and osteochondritis, stress fracture, or tendinitis was difficult toarrive at. We were only able to conclude that the radiographic abnormalities and consequently the etiology of the syndrome vary, and therefore there is a limitation to call the syndrome accompanied by abnormal findings of the inferior pole of the patella under the umbrella term of SLJD. (Keio J Med 58 (1) : 50－53, March 2009)

Keywords: Sinding-Larsen-Johansson disease, patella, calcification, juvenile athlete
Introduction

diographic configuration of the area; and stage 4B, a coalesced calcification mass separated from the patella.3
Clinically, however, radiographic abnormalities at the inferior patella seem to vary; there are several pathogeneses reported; apophysitis, periostitis, tendinitis, calcification accompanied by avascular necrosis, or osteochondritis.2, 4, 5 The etiology of the syndrome seems not to beunified. SLJD appears to be rare, because the incidenceof radiographic abnormalities at the inferior pole of thepatella has been suggested to be low (2-5%) in healthyjuveniles (10-14 years of age).5 We have experienced
seven cases (juvenile athletes) diagnosed as having
SLJD. In this paper, we discuss the etiology of the syndrome based on our examination of radiographs of theinferior pole of the patella in the seven cases of SLJD.

In 1991 and 1992 Sinding-Larsen and Johansson respectively and independently described a syndrome, in
the adolescent consisting of tenderness at the inferiorpole of the patella accompanied by radiographic evidence of fragmentation of the pole.1, 2 This is the Sinding-Larsen-Johansson disease (SLJD), and has been used
as an umbrella term for the syndrome that causes pain of
the inferior pole of the patella accompanied by fragmentation of the pole or a calcification at the pole.
Medlar identified four radiographic stages of the disease process: stage 1, normal findings; stage 2, irregularcalcifications at the inferior pole of the patella; stage 3,
coalescence of the calcification; stage 4A, incorporationof the calcification into the patella to yield a normal ra-

Reprint requests to: Jun Iwamoto, MD, Institute for Integrated Sports Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo
160-8582, Japan, Tel: +81-3-3353-1211; Fax: +81-3-3352-9467; E mail: jiwamoto@sc.itc.keio.ac.jp50

Keio J Med 2009; 58 (1):50－53

51

Table 1 Study subjects
Case

GenderSymptomatic side

Sporting activity

Treatment for SLJD

1

Age(years)
11

Male

Left

Soccer/Karate

Conservative

Time until return tooriginal sporting activity
6 weeks

2

11

Male

Left

SoccerConservative

12 weeks

3

11

Male

Left

SkiingConservative

14 weeks

4

12

Male

Left

SoccerConservative

8 weeks

5

13

Male

Bilateral

Kendo

Conservative

6

12

Male

Right

SoccerConservative

7

12

Male

Right

SoccerConservative

Surgery(Meniscectomy due to meniscus injury)

8 weeks
8 weeks

Conservative treatment: stopping sporting activities and stretching of the quadriceps and hamstrings.

Fig. 1 Case 1: 11-year-old male soccer/karate athlete

Case Reports
Table 1 shows the seven cases that we investigated inthis study. All of them were male athletes, and the age ofthe subjects was 11－13 years.
Case 1 (11-year-old male soccer and karate athlete,Fig. 1): incorporation of the calcification into the patella
to yield a normal radiographic configuration of the area(stage 4A) was found in the right asymptomatic knee.
On the other hand, coalescence of the calcification (stage3) was found in the left symptomatic knee. There wastenderness at the inferior pole of the patella in the left
knee. Clinically, it was not clearly distinguished from either osteochondritis or stress fracture.
Case 2 (11-year-old male soccer athlete, Fig. 2): regular and irregular calcifications (no corresponding stage
and stage 2, respectively) were found in the right asymptomatic and left symptomatic knees, respectively. Irregularity of the inferior pole of the patella was also found in

Fig. 2 Case 2: 11-year-old male soccer athlete

the left symptomatic knee. There was tenderness at theinferior pole of the patella in the left knee.
Case 3 (11-year-old male skiing athlete, Fig. 3): there
were no abnormal findings in the right asymptomaticknee. On the other hand, a small calcification separated
from the patella (no corresponding stage) was found in
the left symptomatic knee. There was tenderness at theinferior pole of the patella in the left knee. It had a similar symptom to tendinitis.
Case 4 (12-year-old male soccer athlete, Fig. 4): irregularity of the inferior pole of the patella and a regularcalcification (no corresponding stage) were found in theright asymptomatic knee. On the other hand, coalescenceof the calcification (stage 3) was found in the left symptomatic knee. There was tenderness at the inferior poleof the patella in the left knee.
Case 5 (13-year-old male kendo athlete, Fig. 5): incorporation of the calcification into the patella to yield anormal radiographic configuration of the area (stage 4A)

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Iwamoto J, et al: Radiographic Abnormalities of SLJD

Fig. 3 Case 3: 11-year-old male skiing athlete
Fig. 6 Cases 6 and 7: 12-year-old male athletes

was seen in the bilateral symptomatic knees. There wastenderness at the inferior pole of the patella.
Cases 6 and 7 (both 12-year old male soccer athletes,
Fig. 6): regular and irregular calcifications (no corresponding stage and stage 2, respectively) were found in
the right symptomatic knees of cases 6 and 7, respectively. There was tenderness at the inferior pole of the patellain the right knee. No radiographs were obtained of thetwo left asymptomatic knees.
Discussion

Fig. 4 Case 4: 12-year-old male soccer athlete

Fig. 5 Case 5: 13-year-old male kendo athlete

The purpose of this case study was to discuss the etiology of the syndrome based on our examination of radiographs of the inferior pole of the patella in the seven cases of SLJD. Among eight symptomatic knees, a regularor irregular calcification (the latter: stage 2) was found at
the inferior pole of the patella in three knees; coalescence of the calcification (stage 3) was found in two
knees; incorporation of the calcification into the patella
to yield a normal radiographic configuration of the area(stage 4A) was found in two knees; and a small calcification separated from the patella was found in one knee.
All of these findings varied and did not always correspond to the radiographic stages identified by Medlar.3
Even in asymptomatic knees, a regular calcification at
the inferior pole of the patella, or incorporation of thecalcification into the patella to yield a normal radiographic configuration of the area (corresponding to stage
4A) was found. This fact indicates that radiographic abnormalities at the inferior pole of the patella are not always associated with symptoms in juvenile athletes,
which could possibly make the etiology of SLJD more
complicated.

Keio J Med 2009; 58 (1):50－53

Injuries in which a differential diagnosis with SLJD is
required are considered to be sleeve fracture, osteochondritis and stress fracture of the patella, and tendinitis of
the patellar tendon. In particular, sleeve fracture, osteochondritis, and stress fracture are hardly distinguishedbased on the radiographic findings. Because orthopaedic
treatment depends on the type of injuries (i.e., major
trauma or over-use; bone and cartilage lesions or tendon
lesion), the differential diagnosis of SLJD from other injuries is important. SLJD results from over-use, whereasa sleeve fracture is caused by a major trauma. Therefore
the differential diagnosis between SLJD and sleeve fracture would appear to be easy from the onset of the symptom. On the other hand, the stress fracture is defined as apartial or complete fracture of bone that results from therepeated application of a stress lower than that required
to fracture the bone in a single loading situation.6 Osteochondritis is related to over-use, such as little leaguer elbow and shoulder, and is included in the definition ofstress fracture. Thus, SLJD in the case 1 was not clearly
distinguished from either osteochondritis or stress fracture. Rather, osteochondritis or stress fracture could possibly contribute to the etiology of SLJD. The strategy oforthopaedic treatment for over-use injuries including
SLDJ, osteochondritis, and stress fracture might be consistent. Moreover, SLJD and tendinitis in terms of socalled jumper’s knee in adult athletes could be combinedin some cases. Therefore, case 3 could be diagnosed ashaving both SLJD and tendinitis. Further studies using
magnetic resonance images and pathological examination are needed to clarify the clear differences between
SLDJ and osteochondritis, stress fracture, or tendinitis.
Thus, the etiology of the syndrome seems not to be unified.
We have also experienced two cases of jumper’s knee
accompanied by ossification in adult baseball and bas-53

ketball athletes (radiographs not shown). Pathologicalexamination of the former athlete showed ossification
inside the patellar tendon. However, these cases correspond to the adult variety of SLJD suggested by Smillie.7
The symptoms caused by SLJD would appear to be
mild. Most of the cases in this report returned to their
original sporting activities in 6-14 weeks except for thecase that showed the similar symptom to tendinitis orneeded a meniscectomy, suggesting the good prognosis
of SLJD.
In conclusion, we examined radiographs of the inferiorpole of the patella in seven juvenile athletes diagnosed ashaving SLJD and discussed the etiology of the syndrome. The radiographic abnormalities and consequently
the etiology of the syndrome vary, and therefore there isa limitation to call the syndrome accompanied by abnormal findings of the inferior pole of the patella under theumbrella term of SLJD.
References
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