Anatomy in Practice
Anatomy in practice: the Popliteus muscle
Stephanie Woodley BPhty MSc
PhD student
Department of Anatomy & Structural Biology
University of Otago
Dunedin
New Zealand
Susan Mercer BPhty(Hons) MSc PhD
Department of Anatomy & Developmental Biology
School of Biomedical Sciences
The University of Queensland
Australia
ABSTRACT
Examination for trigger points in the popliteus muscle involves palpation of its
muscle belly and proximal tendon of attachment. Review of the popliteus muscle
in situ revealed its location on the oor of the popliteal fossa and the association of
overlying soft tissues and neurovascular bundles. While the premise in clinical texts
is that this muscle is easily accessible, the clinical anatomy of popliteus highlights
that palpation is not as straightforward as often depicted.
Woodley S, Mercer S (2006): Anatomy in practice: the Popliteus muscle. New Zealand
Journal of Physiotherapy 34(1): 25-29.
INTRODUCTION
The differential diagnosis for posterior knee
pain can be complex, and vascular and neurologic
pathology needs to be considered alongside
musculoskeletal disorders (Muche and Lento 2004).
From a musculoskeletal perspective, popliteus has
been implicated in complaints of posterior knee
pain that is exacerbated with activities such as
crouching and either walking or running, downhill
or downstairs. One suggestion regarding the pattern
of pain referral from popliteus is that it arises from
an active trigger point located within the middle
of its muscle belly. In addition, if symptomatic,
the popliteal tendon and the region of its femoral
attachment may be tender when palpated. When
describing techniques of palpation it has been
proposed that the tibial attachment, the upper
lateral end of popliteus and the femoral attachment
are palpable (Chaitow and Walker DeLany 2002,
Travell and Simons 1999). Interestingly, the
topography of the muscle is not included in these
clinical descriptions. As the morphology of the
popliteus muscle in situ is rarely discussed in
relationship to musculoskeletal assessment of
the knee region, the purpose of this paper was to
present the clinical anatomy of this muscle.
Morphology
Popliteus is described as a thin or attened
triangular shaped muscle. Its broad muscle belly
attaches medially to the posterior surface of the
tibia above the soleal line, tapering to an apex as
it approaches the knee joint (Figure 1) (Grant and
Basmajian 1965, Hollinshead 1969, Gardner et al
1975). From their distal attachment, the fascicles
of popliteus pass superiorly and laterally, running
beneath the arcuate ligament (Last 1948, Watanabe
et al 1993). Becoming tendinous, it then passes
between the brous and synovial layers of the knee
NZ Journal of Physiotherapy – March 2006, Vol. 34 (1)
joint capsule, and continues upwards towards its
proximal insertion. Attachment proximally is into
the lateral surface of the lateral condyle of the
femur, below the attachment of the lateral collateral
ligament (Figure 2) (Frazer 1940, Hollinshead 1969,
Watanabe et al 1993). A bursa is found deep to the
tendon where it passes between the lateral collateral
ligament and the lateral meniscus.
Clear associations between popliteus and
surrounding structures have been identied. A
feature of its eshy attachment to the tibia is that it
is covered by dense fascia, which is particularly thick
medially, thereby acting as an aponeurosis for the
semimembranosus muscle (Grant and Basmajian
1965, Moore and Dalley 2006). Associations have
also been observed with the joint capsule, lateral
meniscus, posterior cruciate ligament, ligaments of
Wrisberg and Humphrey, oblique popliteal ligament,
the arcuate ligament complex, and to the head of
the bula (Figure 1) (Jones et al 1995, Kimura et
al 1992, Last 1948, Last 1950, Terry and LaPrade
1996, Tria et al 1989, Ullrich et al 2002, Wadia et
al 2003, Watanabe et al 2003).
Function
Popliteus provides posterolateral stability to
the knee joint and aids in stabilising the lateral
meniscus and controlling tibial rotation (Jones et
al 1995, Muche and Lento 2004, Nyland et al 2005,
Ullrich et al 2002). This muscle is not thought to
contribute signicantly to exion of the knee joint
(Fuss 1989, Kaplan 1962, Moore and Dalley 2006).
However, it has been suggested that popliteus aids
in unlocking and internally rotating the knee joint
when initiating exion, and that it may control
antero-posterior motion of the lateral meniscus
throughout the motion of exion (Fuss 1992, Last
1948, Moore and Dalley 2006). In instances when
the knee adopts a static exed position, popliteus
25
Figure 2: Lateral view of a right knee joint. The tendon
of popliteus (PT) is attaching to the lateral aspect of
the lateral femoral condyle (LFC), below the proximal
attachment of the lateral collateral ligament (LCL).
Lateral meniscus (LM), head of the bula (F).
Figure 1: Posterior view of a left knee joint. The popliteus
muscle (P) runs superiorly from the tibial shaft medially
above the oblique soleal line (S), to pass under part
of the arcuate ligament complex (AL) and lateral
collateral ligament (LCL). It attaches to the lateral
femoral condyle via its tendon (PT). Note the groove
for the popliteal tendon in the lateral femoral condyle
(arrowhead). Fibula (F), posterior cruciate ligament
(PCL), ligament of Wrisberg (LW), insertions of the
lateral head of gastrocnemius (LG) and medial head of
gastrocnemius (MG).
is also thought to assist the posterior cruciate
ligament in preventing anterior displacement of
the femur on the tibia (Moore and Dalley 2006). As
this paper is concerned with the morphology of the
popliteus muscle, readers interested in the function
of this muscle are referred to a recent review (Nyland
et al 2005).
Popliteal Fossa
When contemplating palpation of popliteus,
the muscle must be considered in situ. From
a physiotherapy perspective, familiarity with
the anatomy of the popliteal fossa is therefore
necessary.
26
Located at the back of the knee, the popliteal fossa
is a diamond shaped area which may be divided into
an upper and a lower triangle. The upper triangle is
bounded medially by the semimembranosus muscle
and overlying semitendinosus tendon. The short
head of biceps femoris, overlaid and fused with the
long head of biceps femoris, forms the lateral border
(Figure 3). These muscles and tendons embrace
the proximal sides of the lower triangle which are
comprised of the two heads of gastrocnemius and
the very small plantaris muscle, which lies beneath
the lateral head. The oor of the fossa is largely
formed by the posterior aspect of the distal femur
which is covered by fat, and the posterior capsule
of the knee joint. The thick fascia covering the
popliteus muscle completes the oor distally (Figure
4) (Grant and Basmajian 1965, Hollinshead 1969,
Woodburne and Burkel 1988). Covering the fossa
to form a roof are the dense, circularly arranged
bres of the fascia lata, which pass distally to
become continuous with the deep fascia of the leg.
It has been suggested that this overlying popliteal
fascia is tensioned when the knee joint is extended
(Gardner et al 1975).
The popliteal fossa contains numerous structures
including the common peroneal and tibial nerves,
popliteal artery and vein, posterior femoral
cutaneous nerve, the genicular branch of the
obturator nerve, the small saphenous vein, lymph
nodes, bursae and fat (Figure 4). All of these various
structures must be considered when attempting to
palpate the popliteus muscle as they lie between
the skin and the popliteus muscle (Hollinshead
NZ Journal of Physiotherapy – March 2006, Vol. 34 (1)
Figure 3: View of a right popliteal fossa from behind. The
boundaries are: upper medial, the semimembranosus
muscle (SM) and overlying tendon of semitendinosus
(ST); upper lateral, the biceps femoris muscle anked
by the common peroneal nerve (CP) and iliotibial
band (ITB) with the vastus lateralis (VL) and fascia lata
(FL); the lower lateral boundary, the lateral head of
gastrocnemius (LG) and the lower medial boundary,
the medial head of gastrocnemius.
1969, Gardner et al 1975, Woodburne and Burkel
1988)
In the midline, the oor is crossed vertically by
the tibial nerve and popliteal vessels (Figure 4).
The popliteal artery lies on the fascia covering the
popliteus. In the upper part of the fossa, the lateral
and medial superior genicular arteries arise from
the popliteal artery, while the middle genicular
artery arises behind the knee joint. Important to
the therapist considering the popliteus muscle,
the medial and lateral genicular branches pass
medially and laterally over popliteus to run deep
to their corresponding collateral ligaments before
NZ Journal of Physiotherapy – March 2006, Vol. 34 (1)
Figure 4: Posteromedial view of a right popliteal
fossa with the medial (MG) and lateral (LG) heads
of gastrocnemius resected to reveal its contents.
The tendon of semitendinous (ST) passes over the
semimembranosus muscle (SM) which anks the medial
head of gastrocnemius. The thick distal expansion (E)
of semimembranosus can be seen covering the medial
muscle belly of popliteus (P). The midbelly and lateral
aspect of the popliteus belly is covered by the tibial
nerve (TN), popliteal vessels (PV), plantaris muscle (Pl),
the common peroneal nerve (CP) and lateral head of
gastrocnemius (LG) with its associated neurovascular
bundle. The lesser saphenous vein (SV) can be seen
approaching the popliteal vein. Soleus (S).
joining the arterial anastomosis around the knee
joint. The terminal branches of the popliteal artery,
the anterior and posterior tibial arteries, arise at
the lower border of popliteus. Typically the lesser
27
saphenous vein pierces the popliteal fascia, passing
between the two heads of gastrocnemius to drain
into the popliteal vein (Grant and Basmajian 1965,
Hollinshead 1969, Gardner et al 1975, Woodburne
and Burkel 1988, Moore and Dalley 2006).
In the upper lateral corner the common
peroneal nerve passes close to the medial border
of biceps femoris. This nerve follows the biceps
tendon as it passes out of the fossa, over the
lateral head of gastrocnemius, to the back of the
head of the bula (Figure 3). Located within the
fossa, the tibial nerve lies in the midline on the
popliteus muscle before passing distally, deep to
the brous arch of the soleus muscle (Figure 4)
(Hollinshead 1969).
Implications for Palpation
Palpation of the popliteus muscle must occur
through the overlying structures of the popliteal
fossa. Consequently the site of the midbelly
trigger point (Chaitow and Walker DeLany 2002,
Travell and Simons 1999) is buried deep beneath
skin, subcutaneous tissue, deep fascia, the
gastrocnemius muscle and the overlying dense
fascia of the popliteus muscle (Figure 5). In addition
the tibial nerve and popliteal vessels pass over the
muscle (Figures 3 and 4).
Popliteus is considered to be most accessible at
two locations - close to the lower medial end, and
to the upper lateral end of the muscle belly (Figure
1). It has been proposed that the lower medial end
of the muscle can be palpated directly between the
semitendinosus tendon and the medial head of the
gastrocnemius muscle (Figures 3 and 4) (Travell and
Simons 1999). To access this area, once, and if it
is possible that the medial head of gastrocnemius
can be pushed laterally, contact with popliteus
would be restricted by overlying skin, subcutaneous
tissue, the crural fascia, and the overlying dense
aponeurosis of the semimembranosus muscle
(Figures 4 and 5). The upper, lateral end of popliteus
is said to be best palpated as it crosses the knee
joint just above the head of the bula, between the
tendon of biceps femoris and the lateral head of
gastrocnemius (Travell and Simons 1999) (Figures 3
and 4). Laterally, the overlying skin, subcutaneous
tissue, crural fascia, tendon of biceps femoris,
common peroneal nerve and arcuate ligament
complex would obstruct direct access to the muscle
(Figures 1, 3-5).
Travell and Simons (1999) have also stated
that when popliteus is involved in the complaint
of posterior knee pain, patient examination will
reveal tenderness of its tendon as well as the region
over its tendinous attachment to the femur. When
palpating in the area of its proximal attachment
the presence of other local structures also require
consideration. These include the lateral collateral
ligament, lateral meniscus, the bursa deep to
popliteus, a tendinous expansion from vastus
lateralis, the tendon of biceps femoris, fascia lata,
and the joint capsule (Figures 2 and 3).
28
Figure 5: Transverse section through a left leg. The
popliteus muscle (P) lies against the tibia (T), anked by
the bula laterally (F). Covered from behind by the skin
(S), subcutaneous tissue (ST), crural fascia (CF), medial
(MG) and lateral (LG) heads of gastrocnemius. Passing
in the midline are the popliteal vessels and the tibial
nerve (TN). Patellar ligament (PL).
CONCLUSIONS
Examination of the popliteus muscle in situ
reveals those soft tissues that would hamper specic
palpation of the popliteus muscle. In addition to
the skin and subcutaneous tissue supercially, a
medial approach encounters the substantial crural
fascia, medial head of gastrocnemius and the dense
aponeurosis of semimembranosus. Laterally, tissues
such as the crural fascia, tendon of biceps femoris,
common peroneal nerve and arcuate ligament
impede direct access to the muscle. Potential pain
generating structures such as the lateral collateral
ligament, lateral meniscus, bursae and the joint
capsule should also be considered when attempting to
palpate the popliteal tendon near its femoral insertion.
Physiotherapists assessing the posterior aspect of the
knee joint should be aware of the morphology and
relations of the popliteal muscle and its tendon.
Key Points
• The in situ morphology of popliteus is complex
as this musculotendinous unit is associated with,
and attached to, numerous soft tissues and
neurovascular bundles
• Popliteus is located deep, close to the oor of
the popliteal fossa
• Physiotherapists considering palpation of
popliteus need to have an awareness of the
location of this muscle in relation to tissues which
overlie and surround it.
ACKNOWLEDGEMENTS
The authors which to thank Mrs Shannon O’Neill, Mr Brynley
Crosado and Mr Russell Barnett for the preparation of the
material used to illustrate this paper. This material forms part of
the teaching collection of the Department of Anatomy and
Structural Biology at the University of Otago.
NZ Journal of Physiotherapy – March 2006, Vol. 34 (1)
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ADDRESS FOR CORRESPONDENCE
Stephanie Woodley, Department of Anatomy & Structural
Biology, University of Otago, Dunedin, New Zealand. Dr Susan
Mercer, Department of Anatomy & Developmental Biology,
School of Biomedical Sciences, The University of Queensland,
Australia Q 4072. Email: s.mercer@uq.edu.au
29
NZSP
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