The Relation of the Femoral Physis and the Medial
Kevin G. Shea, M.D., Nathan L. Grimm, B.S., Jen Belzer, B.S., Robert T. Burks, M.D., and
Ronald Pfeiffer, Ed.D., A.T.C.
Purpose: The purpose of this study was to determine the origin of the medial patellofemoral ligament
(MPFL) relative to the distal femoral physis by use of an indirect radiologic method. Methods:
Twenty radiographs from adolescent male and female subjects (10 samples from each group) were
used. The subjects studied were all skeletally immature, with an open distal femoral physis. The
radiographic technique described by Schöttle et al. was used to identify the origin of the MPFL.
Imaging software was used to determine the approximate distance of the MPFL origin relative to the
open growth plate of the subjects involved. Results: In all 20 radiographs the medial physis was
found to be distal to the average MPFL insertion point. The mean location for the female physis was
2.7 ? 1.1 mm distal to the MPFL origin. The mean location for the male physis was 4.6 ? 2.4 mm
distal to the MPFL origin. Conclusions: Based on an indirect radiographic technique, we found that
the origin of the MPFL is just proximal to the femoral physis. Clinical Relevance: This information
may be useful when planning medial retinacular surgical procedures in skeletally immature athletes
to help avoid clinically significant physeal injury.
frequent causes of acute hemarthrosis in young ath-
letes.2-5Studies have shown an annual incidence of
this injury of 5.8 per 100,000 persons, with studies in
pediatric/adolescent patients having a higher inci-
dence of 43 per 100,000 persons.6In a large epidemi-
ologic study by Fithian et al.,7female patients aged 10
to 17 years had the highest rates of repeat patellar
atellar dislocation is a common injury in the skel-
etally immature patient1and is one of the most
Many young athletes with patellar dislocation have
an open physis. The importance of the medial patel-
lofemoral ligament (MPFL) as the primary restraint to
patellar dislocation has been analyzed in many recent
biomechanical studies.8,9However, the relation be-
tween the origin of the MPFL and the distal femoral
physis has not been well defined in the literature.
Cadaveric tissue studies in adults have defined the
anatomy of the MPFL and its femoral origin.10-12
Using cadaveric specimens, Schöttle et al.13have de-
veloped a radiographic technique that allows for the
intraoperative identification of the origin of the MPFL
using radiographic landmarks. Cadaveric studies in
children are very difficult to conduct, because skele-
tally immature specimens are not readily available for
research purposes. For this reason, anatomic studies in
children may need to be based on radiographic or
magnetic resonance imaging techniques. Because pe-
diatric cadaveric specimens are not available for such
studies, the radiographic technique of Schöttle et al.
was used to identify the femoral origin from radio-
graphs of skeletally immature knees.
From Intermountain Orthopaedics (K.G.S., N.L.G.); Saint Alphon-
sus Regional Medical Center (K.G.S.); and Department of Kinesi-
ology, Boise State University (R.P.), Boise, Idaho; the Medical
College of Wisconsin (J.B.), Milwaukee, Wisconsin; and the De-
partment of Orthopaedics, University of Utah (R.T.B.), Salt Lake
City, Utah, U.S.A.
The authors report no conflict of interest.
Received July 8, 2009; accepted December 14, 2009.
Address correspondence and reprint requests to Kevin G. Shea,
M.D., 600 N Robbins Rd, Ste 400, Boise, ID 83702, U.S.A. E-mail:
© 2010 by the Arthroscopy Association of North America
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 26, No 8 (August), 2010: pp 1083-1087
Knee reconstruction procedures that include surgi-
cal dissection of the physis include the risk of produc-
ing iatrogenic growth disturbance, leading to angular
deformity and/or length discrepancy. Thus the loca-
tion of the origin of the MPFL and its relation to the
medial distal femoral physis is important if MPFL
reconstruction is to be performed.
The purpose of this study was to define the relation
between the distal femoral physis and the origin of the
MPFL. Our hypothesis was that an indirect radiologic
method to determine the origin of the MPFL could be
used to reliably identify the midpoint of the origin of
the MPFL with respect to the distal femoral physis.
This study was approved by the institutional review
board. By use of a database of digital radiographs,
images were identified through a computerized search.
The search protocol was used to identify 10 male
subjects (aged 14 to 15 years) and 10 female subjects
(aged 12 to 13 years). At this age, these patients are
approaching skeletal maturity, which will minimize
the differences between the adult knee anatomy and
those of the patients used in this study. Lateral knee
radiographs of skeletally immature subjects were used
for the study. Images were obtained with the patient in
the supine position, with partial knee flexion (up to 90°)
and both posterior condyles projected in the same plane.
The lateral images were viewed with the MedView ap-
plication (version 126.96.36.199; Aspyra, Jacksonville, FL) on
an Aspyra AccessNet system allowing the user to draw
lines with measured lengths and angles.
The subjects studied in this series were all skeletally
immature, with an open distal femoral physis. The
mean age was 12.73 years for female subjects and
14.58 years for male subjects. The age/sex relation
was chosen to provide quality images with defined
physis and anatomic landmarks deemed necessary to
determine the femoral origin of the MPFL by use of
the following method as described by Schöttle et al.13
By use of the Cobb feature from MedView (to
ensure angle accuracy), an extended line was drawn
distally from the posterior femoral cortex (line 1, Fig
1). Two perpendicular lines were then drawn: one
intersected point 1, the point of inflection of the pos-
terior origin of the medial femoral condyle to the
posterior cortex (line 2, Fig 1). The final perpendicular
line (line 3, Fig 1) intersected the posterior femoral
extension and posterior aspect of the intercondylar
notch line (point 2, Fig 1). By use of MedView’s ruler
feature, lines were drawn 1.3 mm anterior to the
posterior cortex extension line (line 1) and 2.5 mm
distal from line 2. The point of intersection was deter-
mined as described by Schöttle et al.13to be the mean
femoral attachment site of the MPFL. The distance from
physis was determined with the ruler feature.
In all 20 radiographs the medial physis was found to
be distal to the average MPFL insertion point. The
mean location for the female physis was 2.7 ? 1.1 mm
distal to the MPFL origin. The mean location for the
male physis was 4.6 ? 2.4 mm distal to the MPFL
origin. Figure 2 shows the mean position of the male
physis and female physis.
The principal findings of our study showed that the
midpoint of the origin of the MPFL in male patients
and female patients is 2 to 5 mm proximal to the
medial femoral physis. In skeletally immature patients
with recurrent patellar dislocations, surgical repair of
MPFL relative to distal femoral physis. The ori-
gin is found adjacent to line 1, between lines 2
and 3. The red dot indicates the midpoint of the
Markers/lines indicating origin of
K. G. SHEA ET AL.
the MPFL may be an option. Reconstruction of the
MPFL in skeletally immature patients may also be an
option in select patients, especially those close to
skeletal maturity with minimal growth remaining. In
patients with significant growth remaining, recon-
struction of the MPFL may place the femoral physis at
risk, leading to growth disturbance.
Although the medial retinacular tissue complex lim-
its the lateral displacement of the patella, the MPFL is
one of the primary restraints to patellar dislocation.8,14
Injury to this ligament is common during patellar
dislocation.8,15Biomechanical studies have shown this
to be one of the main soft-tissue structures preventing
lateral patellar dislocations.8,10,14-17Other structures
contribute to stability of the patella with respect to
lateral subluxation, including the menisco-patellar and
tibio-patellar ligaments, and the dynamic contribution
of the vastus medialis obliquus muscle.18,19
The MPFL originates from the adductor tubercle
region of the femoral condyle, travels transversely, and
attaches to the upper two-thirds of the medial patellar
border.8,10,11,15The adductor tubercle is closely associ-
ated with the distal femoral physis. Different methods
have been used to study ligamentous structures about
the knee in young subjects, including studies in still-
born infants20and magnetic resonance imaging stud-
ies.12,21Because of the lack of anatomic specimens in
these age groups, studies using indirect anatomic
methods will be important to establish anatomic land-
marks in young patients.
Procedures that repair and/or reconstruct the MPFL
are used to treat recurrent dislocation in athletes.22-25
Anatomic reconstruction of this ligament, with an
emphasis on ligament isometry and the use of precise
anatomic landmarks, may better reproduce the anat-
omy and kinematics of this structure.8,14,25-35Ana-
tomic procedures that attempt to reproduce the normal
mechanical function should emphasize the use of pre-
cise landmarks. The distal femur and proximal tibia
should be approached carefully during ligament re-
construction procedures. Several studies have shown
that both of these areas are vulnerable to clinically
Average distance of MPFL origin relative to femoral physis.
MPFL AND DISTAL FEMORAL PHYSIS
significant physeal arrest during anterior cruciate lig-
ament reconstruction in the skeletally immature pa-
tient.36-38During the repair and/or reconstruction of the
MPFL in skeletally immature subjects, these anatomic
landmarks should be considered to determine the best
location for the ligament femoral origin and potentially
reduce the risk of physeal injury.
This study showed that the femoral origin of the
MPFL is typically within 2 to 5 mm of the distal
femoral physis. When performing any reconstruction
of the MPFL in a skeletally immature subject with
significant growth remaining, one should consider the
relation. To avoid physeal injury, it may be best to
repair the existing structures rather than to use a drill
hole or an anchoring device near the origin of the
ligament on the distal femur in patients with signifi-
cant growth remaining.
There are several limitations to this study, including
the use of a finite number of radiographs. The use of
a direct anatomic study of skeletally immature sub-
jects would be preferable over the use of an indirect
radiographic technique. However, cadavers of skele-
tally immature subjects are very difficult to obtain.
Despite an extensive search throughout the United
States, we were unable to locate any such cadavers.
The use of an indirect radiographic technique devel-
oped for adult patients may also not be directly appli-
cable to skeletally immature subjects. To address this
concern, subjects were selected who were close to
skeletal maturity. The knees at this age have minimal
growth remaining and should give a better approxi-
mation of the adult knee.
Based on an indirect radiographic technique, we
found that the origin of the MPFL is just proximal to
the femoral physis.
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MPFL AND DISTAL FEMORAL PHYSIS