This document provides an overview of knee deformities in cerebral palsy and treatments for flexion deformity. It discusses how the hip and knee are related through connecting muscles. Flexion deformity is the most common knee issue and can be caused by tight hamstrings, weak quads, or other factors. Evaluation involves assessing various muscles for spasticity and strength. Common surgical techniques discussed include fractional lengthening of the hamstring tendons and combined hamstring lengthening with posterior capsule release. Distal femoral extension osteotomy with patellar tendon advancement is also summarized.

1. THE KNEE IN CEREBRAL
PALSY
A TOPIC PRESENTATION
by
DR. LIBIN THOMAS MANATHARA
(AMALA INSTITUTE OF MEDICAL SCIENCES, THRISSUR)

2. • PART 1
• Hip and Knee Relationships
• Flexion Deformity
• Fractional Lengthening of Hamstring Tendons
• PART 2
• Combined Hamstring Lengthening, Posterior Capsular Release
• Distal Femoral Extension Osteotomy and Patellar Tendon Advancement
• Distal Transfer of Rectus Femoris
• Rectus Femoris Transfer
• Recurvatum of the Knee
• Knee Valgus
• Patella Alta

3. PART 1

4. HIP AND KNEE
RELATIONSHIPS

5. Hip and Knee Relationships
• Deformities of the knee in patients with cerebral palsy are
difficult to evaluate and treat and rarely occur in isolation
• Pelvic, hip, knee, ankle, and foot deformities are interrelated

6. Hip and Knee Relationships
• The hip and the knee are tightly coupled because of the
muscles that cross both joints, the “two-joint muscles.”
• These muscles include the rectus femoris anteriorly, gracilis
medially, and semimembranosus, semitendinosus, and
biceps femoris posteriorly

9. Hip and Knee Relationships
• Pathological conditions that affect these muscles, such as
spasticity or contracture affect the function of both joints
• A similar relationship exists between the knee and ankle with
the gastrocnemius muscle, which crosses both joints

10. Hip and Knee Relationships
• A patient with cerebral palsy who ambulates with his or her
knees flexed may not have hamstrings that are tight or
spastic
• A patient with a hip flexion contracture ambulates with
increased knee flexion to help maintain sagittal balance

11. FLEXION DEFORMITY

12. Flexion Deformity
• A careful physical examination of the entire lower extremity
is essential when evaluating the knee in patients with
cerebral palsy
• Flexion is the most common knee deformity in patients with
cerebral palsy and frequently occurs in ambulatory children

13. Flexion Deformity
• Knee flexion deformities keep the knee from fully extending
at the end of the swing phase of gait
• This causes the knee to be flexed during stance phase,
leading to decreased stride length and increased energy
expenditure

14. Gait cycle

15. Flexion Deformity
• Spastic hamstrings, weak quadriceps, or a combination of
both can cause isolated knee flexion
• It also can result from hip or ankle pathology
• Patients with spastic hip flexors or weak hip extensors or
both develop compensatory knee flexion that results in
crouch gait in which the hips, knees, and ankles are flexed
(Fig. 1)

16. Figure 1
Typical jump posture caused by plantar flexion deformities of ankles,
which require flexion of knees, hip, and lumbar spine to place center
of gravity over weight bearing surface.

17. Flexion Deformity
• Patients with weakened gastrocnemius-soleus muscles, from
cerebral palsy or more commonly from Achilles tendon
lengthenings, ambulate with knee flexion to accommodate
for the relative overpull of the ankle dorsiflexors
• Prolonged spasticity and crouched knee gait can lead to true
contracture of the knee itself

18. Flexion Deformity
• This is a difficult problem to deal with and has led to the
increased use of single-event multilevel surgery (SEMLS)
rather than staged procedures
• A wide variety of procedures has been proposed for this,
including femoral shortening or distal femoral extension
osteotomy with patellar tendon advancement or both
• Patellar advancement has been shown to improve gait
mechanics better than extension osteotomy alone

19. Flexion Deformity
• To find the source of the knee flexion, the muscles must be
assessed to determine if the deformity is caused by spasticity
or contracture or both
• Strength testing should be done, although this can be
difficult in patients with cerebral palsy
• Cerebral palsy is an upper motor neuron disorder in which
the brain is geographically affected, causing the body to be
regionally affected

20. Flexion Deformity
• This is different from a lower motor neuron injury, such as a
peripheral nerve laceration, in which only the innervated
muscle or group of muscles is affected
• In patients with cerebral palsy, if the hamstrings are affected,
most likely the quadriceps are affected to some degree as
well

21. Flexion Deformity
• Quadriceps strength, spasticity, and firing pattern should be
evaluated throughout the gait cycle
• Lengthening, and essentially weakening, the hamstrings in
the presence of a spastic rectus femoris can lead to
hyperextension deformity of the knee and significant gait
disturbance

22. Flexion Deformity
• Hamstring strength, spasticity, and knee contracture are
assessed with the patient prone and supine
• With the patient prone, the examiner extends the hips as
much as possible and exerts gentle pressure on the calves
• The angle that the femur and the tibia make after spasticity
has been overcome is the degree of contracture of the soft
tissues behind the knee

23. Flexion Deformity
• Next, the patient is placed supine to test hamstring spasticity
• The examiner stabilizes the opposite knee in as much
extension as possible and raises the leg being examined with
the knee straight
• If knee extension is limited as the hip is flexed, either medial
or lateral hamstring tightness is present (Fig. 2)

24. Figure 2
Testing for hamstring spasticity and
contracture
A, Patient is supine with hips extended
Pressure is exerted over knees, forcing
them into extension
Flexion remaining in knees is absolute knee
flexion contracture
B, Knee on side to be tested is flexed, while
opposite knee is stabilized in extension
C, Attempted flexion of hip results in more
flexion of knee

25. Flexion Deformity
• The patient can be examined for medial hamstring spasticity
in the supine position with the knees flexed and feet off the
table
• This relaxes the hamstrings proximally and allows the hip to
be abducted if there is no contracture of the adductor
muscles
• If extension is not possible unless the hip is adducted, there
is tightness in the medial hamstrings and gracilis (Fig. 3)

26. Figure 3
Testing for adductor and medial hamstring
tightness
A, Thighs abduct well with hips and knees
flexed, indicating no adductor contracture
B, With hips extended and knees flexed, hips
abduct well
C, With hips extended, bringing knees into
extension causes thighs to adduct, indicating
medial hamstring spasticity.

27. Flexion Deformity
• The amount of equinus in the ankle should be measured
with the knee flexed and fully extended (Fig. 4)
• If ankle dorsiflexion improves with knee flexion, there is
gastrocnemius spasticity or contracture

28. Figure 4
Testing for gastrocnemius contracture and
spasticity
A, With knee extended, equinus in ankle is
noted
B, With knee flexed, ankle is easily dorsiflexed,
indicating no soleus contracture
C, As knee is extended, ankle dorsiflexion is
resisted by tight or spastic gastrocnemius
muscles

29. Nils Silfverskiöld (1888-1957) and gastrocnemius contracture
• Nils Silfverskiöld was an
orthopaedic surgeon, Swedish
aristocrat, bon vivant (a person
who devotes themselves to a
sociable and luxurious lifestyle),
Olympic gymnast, left wing
intellectual and anti-Nazi who
described that the force
required to dorsiflex the ankle in
spastic equinus contracture
decreased with knee flexion in
isolated gastrocnemius
contracture

30. Nils Silfverskiöld (1888-1957) and gastrocnemius contracture
• He advocated detaching the origins of the gastrocnemii from
the femur and reattaching them to the tibia
• The Silfverskiöld knee flexion test has now also been adapted
to distinguish between isolated gastrocnemius contracture
and combined shortening of the gastrocnemius-soleus
complex in non-spastic contracture by measuring the range
of ankle dorsiflexion with the knee flexed and the knee
straight

31. Flexion Deformity
• As previously mentioned, it is important to assess quadriceps
strength, contracture, and function when evaluating a
patient with knee flexion deformity
• Quadriceps strength is best assessed with the patient supine
and the feet off the end of the table
• The examiner extends the hips and allows the knees to flex
passively (Fig. 5 A) and then asks the patient to extend the
knees voluntarily against resistance (Fig. 5 B)

32. Figure 5
Testing for quadriceps strength
A, With hips extended, knees
are allowed to flex off end of
table
B, Patient voluntarily extends
knees from flexed position
against resistance.

33. Flexion Deformity
• To determine if the rectus femoris is spastic, the examiner turns the
patient prone and performs the prone rectus (Ely) test (Fig. 6)
• With the patient prone and the knees extended, the examiner flexes
the knees
• If the rectus is spastic, the hips flex and the buttocks rise off the table
when the rectus is stretched
• It is best to do this one side at a time to determine the relative
spasticity of each rectus femoris muscle

34. Figure 6
Prone rectus test
A, Patient is prone, and knees are
extended
B, Flexing knees causes buttocks to
rise from table
C, Spasticity in rectus is overcome
by downward pressure on
buttocks.

35. Flexion Deformity
• Physical therapy and bracing can be used for milder deformities
• Serial stretch casting has been shown to be effective as well, but care
is necessary to prevent soft tissue complications or breakdown and
neurapraxia
• The indications for hamstring lengthening are a straight-leg raise of
less than 70 degrees or a popliteal angle of less than 135 degrees in
the absence of significant bony deformity

36. Flexion Deformity
• In an ambulatory patient, knee contracture of more than 10 degrees
can lead to excessive compensatory hip flexion and ankle dorsiflexion
• Care must be taken not to overlengthen the hamstrings because it
can lead to excessive weakness and knee hyperextension gait
• In hyperextension gait, the femur moves forward over a fixed tibia,
which is prevented from moving forward either by a spastic
gastrocnemius-soleus or a limited ankle dorsiflexion

37. Flexion Deformity
• Rectus femoris spasticity, which is common in patients with cerebral
palsy, also can exacerbate this condition
• For this reason, most surgeons begin with lengthening the medial
hamstrings by a Z-plasty of the gracilis and semitendinosus tendons
and a fractional lengthening of the semimembranosus

38. Flexion Deformity
• If further correction is desired, the biceps femoris laterally can be
lengthened using fractional lengthening
• It is important to identify the proximal aponeurosis of the
semimembranosus anteriorly as it arises from the tendon of the
proximal attachment
• It is separate and proximal from the distal aponeurosis and should be
released at the time of surgery as well

39. FRACTIONAL LENGTHENING
OF HAMSTRING TENDONS

40. Fractional Lengthening of Hamstring Tendons
• Although knee extension in stance phase has been shown to improve
dramatically after hamstring lengthening, velocity, stride length, and
cadence have not been shown to improve
• With spastic hamstrings and quadriceps, knee flexion during swing
phase markedly diminishes

41. Fractional Lengthening of Hamstring Tendons
• In addition, the results of surgery have been reported to deteriorate
with time, with reoperation being necessary in up to 17%
• Some improvement in the popliteal angle and knee extension has
been noted in patients with combined medial and lateral hamstring
lengthenings, however, with greater risk of knee hyperextension and
hamstring weakness

42. TECHNIQUE
• Place the patient prone, and inflate the thigh tourniquet
• Make medial and lateral posterior incisions from the popliteal crease
extending 7 to 10 cm proximally
• Alternatively, a single midline incision can be used (Fig. 7 A)
• Divide the subcutaneous tissue and deep fascia in line with the skin
incision, protecting the posterior femoral cutaneous nerve in the
proximal portion of the wound

43. Figure 7
Fractional lengthening of hamstrings
A, Skin incision and incision in deep fascia over back of knee

44. TECHNIQUE
• Identify the hamstrings by blunt dissection, isolate the
semimembranosus, and incise its tendon sheath longitudinally
• Divide its tendinous fibers on its deep side transversely at two levels
(Fig. 7 B and C)
• Expose the semitendinosus tendon and divide the distal part of the
tendon obliquely up to its muscle fibers
• Incise the tendon transversely or perform a Z-plasty

45. • B and C, Incisions in
semimembranosus

47. TECHNIQUE
• Extend the knee and flex the hip, and the tendinous portion of the
semimembranosus slides on the muscle
• If further correction is required, identify the biceps femoris tendon
laterally, and isolate it from the peroneal nerve lying along its medial
side
• Pass a blunt instrument deep to the biceps femoris tendon, incise its
tendinous portion transversely at two levels 3 cm apart, and leave the
muscle fibers intact (Fig. 7 D)

48. • D, Incisions in
biceps femoris;
note hemostat
anterior to
peroneal nerve

49. TECHNIQUE
• Perform a similar lengthening maneuver by flexing the hip and
extending the knee.
• Close all tendon sheaths, but do not close the deep fascia (Fig. 7 E).
• After deflating the tourniquet, obtain hemostasis and close the
subcutaneous tissues and skin.
• Apply a long-leg cast with the knee in maximal extension.

50. • E, Tendon sheaths of
biceps femoris and
semimembranosus are
sutured before wound
closure

51. TECHNIQUE
• Postoperative Care
• Straight-leg raises are begun immediately postoperatively with the
cast on to help stretch the hamstring tendons
• The patient may walk with crutches and bear weight as tolerated
• After 3 to 4 weeks, the casts are removed and the patient is started
on a physical therapy program to maintain, and in some cases
improve, range of motion
• Night time extension splints or knee immobilizers are used for 8 to 12
weeks postoperatively

52. PART 2

53. COMBINED HAMSTRING
LENGTHENING AND
POSTERIOR CAPSULE
RELEASE

54. Combined Hamstring Lengthening, Posterior
Capsular Release
• If hamstring lengthening alone is ineffective in achieving the desired
range of motion, a posterior capsular release can be used
• This most commonly occurs in older children with significant fixed
knee flexion contractures
• This technique also can be combined with quadriceps shortening to
help correct elongation of the infrapatellar tendon caused by chronic
quadriceps weakening to obtain improved range of motion

55. DISTAL FEMORAL EXTENSION OSTEOTOMY
AND
PATELLAR TENDON ADVANCEMENT

56. Distal Femoral Extension Osteotomy and
Patellar Tendon Advancement
• Stout et al. described a distal femoral extension osteotomy and
patellar tendon advancement for treatment of crouch gait in cerebral
palsy and obtained improved function and level of community
walking ability
• Recurrence of deformity is less likely in patients in whom growth is
complete

57. TECHNIQUE (STOUT ET AL)
• Approach the distal part of the femur posterior to the vastus lateralis
• Insert a chisel for a 90-degree blade plate just proximal to a guidewire
placed at a 90-degree angle to the femoral shaft and just proximal to
the physis (or physeal scar) with the angle guide of the chisel parallel
to the tibia
• This placement avoids varus or valgus displacement of the osteotomy

58. TECHNIQUE
• Remove an anterior triangular wedge of bone that matches the
degree of contracture
• Also, remove any bone protruding posteriorly from the distal
fragment (Fig)
• Coronal and transverse plane abnormalities can be corrected
simultaneously

59. Figure
A and B, Preoperative and postoperative lateral radiographs of left knee in maximal extension in patients treated
with distal femoral extension osteotomy

60. TECHNIQUE
• The type of patellar tendon advancement depends on the skeletal
maturity of the patient
• If the physis is open, sharply divide the patellar tendon from the tibial
tubercle to avoid physeal injury and advance it under a periosteal flap
• If the physis is closed, transpose the tibial tubercle with the attached
patellar tendon distally and secure it with a compression screw
• Insert a 16-gauge wire or tension-band wire transversely through the
patella and the proximal part of the tibia to protect the repair (Fig)

61. A and B- Anteroposterior and lateral radiographs of knee in maximal extension after
patellar tendon advancement

62. DISTAL TRANSFER OF RECTUS
FEMORIS

63. Distal Transfer of Rectus Femoris
• Stiff knee gait is common in patients with cerebral palsy and is caused
by co-contracture of the quadriceps and hamstring muscles or
weakness caused by previous hamstring lengthening, or both
• Co-spasticity of the hamstrings and quadriceps causes a loss of knee
flexion that leads to decreased power and difficulties with foot
clearance during the swing phase of gait

64. Distal Transfer of Rectus Femoris
• Patients with rectus femoris spasticity also have difficulty
transitioning from standing to sitting
• Dynamic EMG analysis often reveals a rectus femoris muscle that also
is abnormally active during swing phase

65. Distal Transfer of Rectus Femoris
• To help achieve balanced knee function during swing phase, transfer
of the distal rectus femoral tendon to the semitendinosus medially or
iliotibial band laterally can be done, depending on the presence of
malrotation
• Ten degrees of malrotation can be corrected depending on the
direction of transfer, but larger degrees of malrotation require
rotational osteotomy of the affected bone

66. Distal Transfer of Rectus Femoris
• Gage et al. found significant improvement in swing-phase knee
motion and foot clearance when the following criteria were met:
• (1) hamstring contractures corrected so that the knee can extend fully
in midstance,
• (2) foot plantigrade and stable in stance, and
• (3) foot in line of progression to generate a moment of sufficient
magnitude to maintain knee extension in midstance and terminal
stance

67. Distal Transfer of Rectus Femoris
• Chambers et al. compared distal transfer of the rectus femoris tendon
with release of the tendon alone and found significantly improved
foot clearance and gait efficiency in the group with tendon transfer
• More improvements than deterioration of results have been reported
in ambulatory children at long-term follow-up

68. TECHNIQUE (GAGE ET AL.)
• With the patient anesthetized and supine, make a longitudinal
incision in the anterior thigh, 5 to 6 cm proximal to the superior pole
of the patella
• Identify the rectus femoris tendon proximally as it lies between the
vastus medialis and vastus lateralis

69. Distal release or transfer of rectus femoris
A- Rectus femoris is separated from vastus medialis, vastus lateralis, and vastus
intermedius
Inset, Longitudinal incision along medial side of distal third of rectus femoris

70. Rectus Femoris Transfer
• Separate the rectus tendon from the remainder of the quadriceps
tendon; avoid entering the knee joint
• Dissect it free to approximately 3 cm proximal to the patella
• Divide the tendon, and separate it from the vastus intermedius
tendon posteriorly

71. Rectus Femoris Transfer
• Transfer the freed tendon stump to either the distal stump of the
semitendinosus or the iliotibial band depending on whether the
desired rotatory effect is lateral rotation (to the iliotibial band) or
medial (to the semitendinosus stump)
• For medial transfer to the semimembranosus, divide the
semimembranosus 2 to 3 cm proximal to its musculotendinous
junction and dissect the distal stump to its insertion at the pes
anserinus

72. Rectus Femoris Transfer
• Transfer the tendon through the medial intermuscular septum, and
suture it to the distal end of the rectus femoris tendon
• For a lateral transfer to the iliotibial band, resect the fibers of the
iliotibial band until the remaining fibers are posterior to the knee joint
axis
• Pass the distal end of the rectus femoris around the iliotibial band,
and suture it onto itself.

73. B- Rectus femoris may be transferred through medial
intermuscular septum to sartorius if desired

74. C- Rectus femoris is sutured to sartorius

75. Rectus Femoris Transfer
• Postoperative Care
• If hamstring lengthening also has been done, patients are placed in
long-leg casts for 3 to 4 weeks
• If hamstring lengthening has not been done, cast immobilization is
unnecessary; instead, a knee immobilizer is used
• The patient is allowed to sit in a reclining wheelchair and is gradually
moved to the upright sitting position with the knee fully flexed

76. Rectus Femoris Transfer
• Standing with support is allowed on the third day, and the knee
immobilizer is removed for passive and active range of motion of the
knee
• At 4 weeks, the patient is instructed by the physical therapist to begin
vigorous exercises to encourage muscle strengthening and gait
training
• Improvements in gait function typically are seen for 12 months
postoperatively

77. RECURVATUM OF THE KNEE

78. Recurvatum of the Knee
• Recurvatum of the knee is caused by a relative imbalance between
the quadriceps and the hamstrings owing to several factors, including
• (1) co-spasticity of the quadriceps and hamstrings in which the
quadriceps is stronge
• (2) weakened hamstrings secondary to previous surgery,
overlengthening, or transfer
• (3) gastrocnemius-soleus weakness secondary to proximal head
recession and
• (4) ankle equinus

79. Recurvatum of the Knee
• For a patient with an ankle equinus contracture, the only way to put
the feet flat is to compensate with knee recurvatum
• The prone rectus test can be used to test for quadriceps spasticity
• If the rectus femoris is tight, it can be lengthened or released in
nonambulatory patients and transferred posteriorly in ambulatory
children
• Recurvatum of the knee caused by excessive hamstring weakness is
difficult to treat

80. Prone rectus test (ELY test)
A, Patient is prone, and knees are
extended
B, Flexing knees causes buttocks to
rise from table
C, Spasticity in rectus is overcome
by downward pressure on
buttocks.

81. Recurvatum of the Knee
• Replantation of transferred tendons or shortening of overlengthened
tendons would not improve functional strength because the muscles
have been permanently weakened by the previous surgery
• To determine if recurvatum of the knee is caused by ankle equinus, a
short-leg cast or ankle orthosis is applied with the ankle in the neutral
position
• If the knee goes into recurvatum with the foot plantigrade, the
recurvatum is not caused by ankle equinus
• If ankle equinus does exist, correction of this operatively or
nonoperatively is indicated

82. Recurvatum of the Knee
• Significant recurvatum should be treated with bilateral long-leg
braces with a pelvic band with the knees locked in 20 degrees of
flexion and ankle stops at 5 degrees of dorsiflexion
• When hip control is achieved, the pelvic band can be removed, but
long leg braces often are used for years until a stable knee is obtained
• Flexion osteotomy for this condition is not advised

83. KNEE VALGUS

84. Knee Valgus
• Knee valgus in patients with cerebral palsy usually is caused by a hip
adduction deformity and rarely occurs independently
• It usually is associated with hip internal rotation and flexion of the
knees, which can accentuate the appearance of valgus
• In most patients, correction of the hip adduction and internal rotation
improves the position and appearance of the knee
• In these patients, surgery on the knee itself is rarely indicated

85. Knee Valgus
• A tight iliotibial band also can cause a knee valgus deformity
• The presence of iliotibial band tightness can be determined by having
the patient lie on the contralateral side and flex the knee nearest the
table to the chest
• With the knee flexed, the hip being tested is flexed and abducted,
moved from the position of flexion to extension, and then adducted
• If the hip does not adduct without flexing, the iliotibial band is tight
and usually can be palpated subcutaneously along the distal third of
the thigh
• The tight band should be resected

86. PATELLA ALTA

87. Patella Alta
• Patella alta is common in patients with cerebral palsy (93% in one
study) and usually is associated with crouched gait (Fig)
• This can be caused by quadriceps spasticity or long-standing knee
flexion deformity
• Patella alta leads to a decrease in the moment arm of terminal knee
extension, which further weakens an already weakened extensor
mechanism

88. Patella alta in patient with cerebral palsy.

89. Patella Alta
• This increased tension can lead to repetitive microtrauma to the
patellar and quadriceps tendons, causing elongation of these
structures and fragmentation and stress fractures of the patella and
tibial tubercle; it is thought to be one of the causes of knee pain in
patients with cerebral palsy
• Because these changes are almost universal in ambulatory patients
with cerebral palsy, and most patients are pain free, operative
treatment rarely is indicated

90. Patella Alta
• Often, correction of the flexion deformity of the knee with hamstring
lengthening and other associated procedures causes improvement in
not only the patella alta but also knee function in general
• Operative treatment to correct the underlying pathological process,
which usually is patellar subluxation and dislocation, is helpful in
patients in whom conservative treatment has failed

91. THANK YOU