Posterior Knee Pain and Its Causes

Transcription

The Physician and Sportsmedicine: Posterior Knee Pain and Its Causes
Posterior Knee Pain and Its Causes
A Clinician's Guide to Expediting Diagnosis
THE PHYSICIAN AND SPORTSMEDICINE - VOL 32 - NO. 3 - MARCH 2004
For CME accreditation information, instructions and learning objectives, click here.
In Brief: Because posterior knee pain is a relatively uncommon patient complaint, its etiology
is challenging and often elusive. The differential diagnosis for posterior knee pain can be vast,
so clues for distinguishing causes are important. Many clinicians are unfamiliar with this
complicated anatomic area and may not have a standard clinical evaluation to establish a cause
of the patient's pain. Review of several known causes of knee pain can provide the examiner
with a more comprehensive list of potential disorders to consider as differential diagnoses when
patients present with posterior knee pain.
It is critical that the examiner obtain a good history when evaluating patients who have
posterior knee pain. Information regarding the onset, duration, location and quality of pain
(using the visual analogue scale), aggravating and alleviating factors, past injuries, operations,
and other treatments, including medications, procedures, rehabilitation, and orthotic use, can
aid with diagnosis. Also significant is knowing whether the pain truly arises from a local source
or is being referred from a more distant source, such as in sacroiliac dysfunction or radicular
pain.
Soft-tissue and tendon injuries are perhaps more common causes of posterior knee pain than
are vascular, neurologic, and iatrogenic injuries, but these less common origins should not be
overlooked in patients who present with posterior knee pain (table 1).
http://www.physsportsmed.com/issues/2004/0304/muche.htm (1 of 12)2/17/2005 9:49:39 AM
TABLE 1. Characteristics of Disorders That Exhibit Posterior Knee Pain
Diagnosis
Distinguishing Symptoms
Support Structures and Tumors
May be asymptomatic; patient
Baker's cyst
may have feeling of fullness in
the popliteal fossa
Physical Findings
Crescent sign; may simulate
venous thrombosis
Soft-tissue or bone tumor
Limited knee flexion; may
Knee locking; palpable
mass; pain without weight bearing mimic a meniscal tear
Meniscal tear
Increasing pain with deep knee
flexion
Point joint-line tenderness;
positive McMurray's test;
effusion
Posterior knee pain with sudden
acceleration or deceleration
Tenderness at distal biceps
femoris tendon; pain with
knee flexion
Posterior knee pain with knee
extension and ankle dorsiflexion
Patient may have tenderness
over areas of CPPD deposition
Pain with running, especially
downhill
Knee flexion with internal
rotation of the tibia in prone
position may cause pain
Varus thrust in stance or with
ambulation; hyperextension,
external rotation; peroneal
nerve may also be injured
Varus thrust; positive external
recurvatum test; positive
dial test
Hypertrophy of calf muscles;
claudication; paresthesias below
the knee
Distal pulses may disappear
with hyperextension and
active plantar flexion or
passive dorsiflexion; trophic
changes below the knee
Tendons
Hamstring injury
Gastrocnemius tendon
calcification
Popliteus tendon injury
Ligaments
Posterolateral corner injury
Blood Vessels
Popliteal artery entrapment
syndrome
Nerves
Common peroneal nerve
entrapment
Tibial nerve entrapment
Iatrogenic
Postsurgical arthrofibrosis
Bioabsorbable tacks
Other
Degenerative joint disease
Tenderness over area of
entrapment; pain may increase
with exertion
Local tenderness over area
of entrapment
Tenderness over area of
entrapment; pain may increase
with exertion
Local tenderness over area
of entrapment
Limited range of motion;
stiffness
Limited knee extension
Sharp posterior knee pain
exacerbated with knee extension
Focal tenderness over points of
tack placement; stable knee
Pain increases with loading;
morning stiffness
Crepitus; limited range of
motion; change in
structural alignment
CPPD = calcium pyrophosphate dihydrate
Baker's Cyst and Tumors
Clinicians should be cognizant of soft-tissue disorders and tumors when examining patients
who report posterior knee pain.
Baker's cyst (popliteal synovial cyst). The popliteal synovial cyst, more commonly known
as Baker's cyst, is a frequently documented source of posterior knee pain. The condition is
caused by a posterior herniation of the synovial membrane or by a communicating
semimembranous bursa into the popliteal space and usually indicates underlying pathology.
This cyst is seen in disorders such as osteoarthritis, rheumatoid arthritis, and internal
derangement of the knee, including meniscal tears.1 However, degenerative arthritis or
meniscal pathology alone may be a potential source of posterior knee pain. In fact, posterior
horn meniscal tears often present with ill-defined posterior knee pain, especially during deep
flexion. Thus, clinicians should examine patients who have posterior knee pain for meniscal
pathology.
Magnetic resonance imaging (MRI) or ultrasound can aid the diagnosis of Baker's cyst. MRI is
advantageous, because it may identify the underlying cause, such as a concomitant meniscal
tear. Focus should be in the most common area for Baker's cyst--along the medial aspect of
the popliteal fossa beneath the medial head of the gastrocnemius.
Even though Baker's cysts are often asymptomatic, they can enlarge or dissect and become
symptomatic, producing joint swelling, pain, or a feeling of fullness in the popliteal fossa.
Occasionally, dissection or rupture may lead to lower-limb swelling, simulating venous
thrombosis. A ruptured cyst usually displays a "crescent sign"--an ecchymotic area around the
malleoli--that may help distinguish this disorder from venous thrombosis.2 Venography or
ultrasonography should be performed if any doubt persists about the diagnosis.
Treatment should address the precluding problem, such as associated meniscal tear or
inflammatory arthritis, but if the cause is unknown, conservative management with the RICE
protocol (rest, ice, compression, and elevation) and nonsteroidal anti-inflammatory medication
can be helpful. Although the cyst may disappear without intervention, some rare cases may
require excision. Unfortunately, surgery may not always provide a cure, because the cyst can
recur and refill, particularly if the underlying derangement is not addressed.
Tumors. Both benign and malignant soft-tissue and bone tumors can also cause posterior
knee pain. Diagnosis of soft-tissue tumors is often delayed, because patients may not come in,
especially in the early stages of tumor growth, and the tumors are difficult to diagnose.
Presenting symptoms of tumors in the posterior knee include pain from pressure of the mass
on adjacent nerves,3 limitation of knee flexion,4 and knee locking with an effusion.5 Some
tumors that cause posterior knee pain include osteochondromas, endochondromas,
chondroblastomas, osteosarcomas, pigmented villonodular synovitis, and synovial
chondromatosis.
Anteroposterior and lateral knee radiographs may show gross formation of a mass. However, if
suspicion for a tumor is high, an MRI with contrast should be obtained for further diagnostic
workup and management. MRI is a useful imaging study, because it can help clinicians
distinguish location, expansion, and characteristics of the tumor. For example, in pigmented
villonodular synovitis, the tumor may clinically mimic a meniscal tear, but MRI can be used to
distinguish between these two entities.6 Similarly, another advantage of a contrast-enhanced
MRI is that one can differentiate a solid tumor from a ganglion cyst, which will only have rim
enhancement.7 MRI can also aid with preoperative staging and planning as well as
postoperative follow-up. In addition, angiography may reveal further anatomic information
about the content of the mass and show any meaningful displacement of nearby vascular
structures. Treatment options may include resection, amputation, radiation, and
chemotherapy, depending on the stage and grade of the lesion.
Affected Tendons
Posterior knee pain can arise from acute tendon strain or chronic injury resulting in tendinitis of
any of the musculotendinous structures in or about the popliteal fossa. Ganglion cysts in the
presence of tendon injury may also contribute to the pain. Some of the more commonly injured
structures posterolaterally include the biceps femoris and the popliteus tendons.
Posteromedially, injuries to the semitendinosus and semimembranosus tendons are more
common. Although they are unusual occurrences, strains or ruptures of the plantaris muscle
may cause posterior knee pain.
Hamstring injury. Although the hamstring tendons consist of the semitendinosus,
semimembranosus, and the long and short heads of the biceps femoris, the most commonly
injured of these is the short head of the biceps femoris. Most hamstring injuries occur around
the musculotendinous junction. However, injury to the tendon itself near the posterolateral
corner of the knee may occur during rapid bursts of running or jumping or during sudden
deceleration. Increased susceptibility to this injury may be from inadequate stretching during
warm-up exercises, decreased flexibility, and muscle fatigue. Endurance sports, such as
running or cycling, are also associated with injury to the biceps femoris tendon.
Physical examination may reveal tenderness at the distal aspect of the biceps femoris tendon
as well as pain during knee extension. If the clinical diagnosis is in doubt, an ultrasound or MRI
may be done. If peripheral neurologic symptoms are present, advanced imaging modalities
may help to rule out a concomitant hematoma that may externally compress adjacent
structures, such as the tibial nerve. MRI may also help physicians determine the prognosis for
return to sport. If more than 50% of cross-sectional muscle or distal myotendinous tears
occur, athletes usually require more than 6 weeks before they may return to sports-specific
programs.8 An earlier return to play may be associated with subtle muscle strength
abnormalities, which can lead to a recurrence of symptoms and possibly worsen the original
tear.9
Gastrocnemius tendon calcification. A rare cause of tendon injury accompanied by
posterior knee pain is calcification of the gastrocnemius tendon as calcium pyrophosphate
dihydrate (CPPD) becomes deposited.10,11 Anteroposterior and lateral knee radiographs may
reveal this phenomenon. CPPD deposition may be seen more often among the elderly; the
involvement of the gastrocnemius tendon is relatively rare in younger patients.12
Popliteus injury. The examiner should also test the popliteus tendon as a possible pain
generator. The popliteus muscle and tendon (figure 1) stabilize the posterolateral corner of the
knee and prevent anterior translation, especially during downhill running. Injury to the
popliteus tendon, therefore, is most commonly seen in athletes who run. The posterolateral
corner is a complex area that is often misunderstood and underrepresented as a cause of
posterior knee pain.
On examination, the popliteus muscle may be tender in the posterolateral corner of the knee.
However, a provocative maneuver that typically provokes pain involves examining the patient
in the prone position with internal rotation of the tibia. The patient then flexes the knee against
resistance. Reproduction of symptoms during flexion suggests injury to the popliteus tendon.
Treatment of a popliteus tendon injury consists of the RICE protocol, gradual stretching
exercises in multiple planes, closed–kinetic-chain eccentric strengthening exercises, such as
slow, multidirectional lunges that patients progress to doing on nonlevel surfaces, and gradual
return to athletic participation. Since these muscle fibers have a rotational component,
rehabilitation should emphasize exercises with rotation.
Other Posterolateral Corner Components
Although the popliteus may be a frequently injured part of the posterolateral corner, other
components include the lateral collateral ligament, the posterolateral capsule, and the
popliteofibular ligament. During the initial 30° of knee flexion, these posterolateral structures
in combination with the posterior cruciate ligament (PCL) are important in resisting excessive
varus orientation, external rotation, and posterior translation of the knee.
Injury mechanism and exam. The most common mechanisms of posterolateral corner injury
involve athletic trauma, motor vehicle collisions, and falls. Isolated injury to this complex
usually derives from a posterolaterally directed force when the knee is in full extension.
Although a patient's initial clinical presentation may involve minimal symptoms, a compromised
posterolateral corner can lead to worsening local symptoms. Patients typically complain of knee
pain while walking and may even develop a varus thrust. Examination may reveal swelling,
abrasion, or ecchymosis. Point tenderness may occur over the fibular head as well as diffusely
in the posterolateral corner. In chronic cases, there may be a varus thrust seen in stance
(figure 2) or during ambulation.
Tests, accompanying injuries, and treatment. The external rotation recurvatum test
(figure 3) can help confirm posterolateral rotary instability. The examiner performs the test by
holding the patient by each great toe and observing any side-to-side differences in
hyperextension, varus, and tibial external rotation.
The dial test also assesses posterolateral rotation of the tibia on the femur to detect
posterolateral knee instability. The patient is supine with 30° of knee flexion and with the foot
extended over the side of the examining table. The examiner externally rotates the foot while
stabilizing the thigh and observes the amount of rotation of the tibial tubercles. Increased
external rotation on the injured side indicates a posterolateral corner injury. If this maneuver is
performed with the knee flexed to 90° and less rotation is seen than when performed at 30°,
then an isolated posterolateral corner injury is probable. If the injured knee rotates more at
90°, then a concomitant PCL injury is likely. Since isolated posterolateral corner injuries are
relatively uncommon and exam maneuvers are often negative, this injury is frequently missed.
The posterior drawer test is more sensitive for detecting PCL-only injury.
Paresthesia and weakness from common peroneal nerve injury may also be present with a
posterolateral corner injury. Researchers have documented that 15% of patients with a
posterolateral knee injury also have a common peroneal nerve injury.13 In their review, Veltri
and Warren14 noted that hemorrhage can be a contributing factor to peroneal nerve palsy in
acute posterolateral corner injury despite an intact nerve. They also noted that in some cases
of lateral and posterolateral corner knee injury, the concomitant varus thrust may lead to
direct injury of the peroneal nerve.
Radiographs taken while the patient is standing may illustrate abnormal widening of the lateral
joint space and arthritis. However, MRI is superior at delineating injury to the structures of the
posterolateral corner.
Nonoperative treatment includes early mobilization with gait retraining and hip girdle
strengthening. The focus should be on quadriceps strengthening, since the quadriceps are most
likely to atrophy in chronic posterolateral instability. Some acute ligamentous injuries warrant
operative repair in the first 3 weeks after injury to provide the optimal result.
Vascular and Nerve Injuries
Injuries to vessels and nerves should not be overlooked in patients with posterior knee pain.
Popliteal artery entrapment syndrome (PAES). This condition arises from hypertrophy of
the medial gastrocnemius, soleus, plantaris, or semimembranosus muscles that compresses
the popliteal artery as it courses through the popliteal fossa. Although the symptoms are most
common in athletes, other cases have been reported in truck drivers, because the same
mechanism causes direct arterial compression. Individuals with rheumatoid arthritis and
associated knee pathology can also present with PAES.15
Symptoms include posterior knee pain and progressive lower-extremity arterial insufficiency
causing claudication of the calf with ambulation or other exertion. Leg swelling, cramping,
coldness, paresthesias, trophic changes, and blanching below the knee may also be present.
On exam, distal pulses decrease or disappear when the knee is in hyperextension with active
plantar flexion or passive dorsiflexion. Other conditions that can mimic PAES include
accelerated atherosclerosis, thromboangiitis obliterans, adventitial cystic disease, adductor
canal outlet syndrome, acute popliteal artery occlusion, microemboli, collagen vascular disease,
Takayasu's arteritis, and coagulopathy.
Several imaging studies can help determine this unusual diagnosis. Duplex ultrasonography
can be used for detection; however, because it is operator dependent, the technique may yield
a high rate of false positives.16 The single most useful study is MRI, since it can illustrate the
area of entrapment as well as determine the patency of the artery if the scan is combined with
special imaging sequences. Although angiography with digital subtraction can be useful in
determining the severity of stenosis, it cannot detect the source of extrinsic compression, and
it is also an invasive study.
Functional stretching can treat the condition, but if that is unsuccessful, then surgical
intervention may be necessary. Surgery usually involves resection of the hypertrophied muscle
to liberate the popliteal artery.
Nerve entrapment. Although rare, common peroneal and tibial nerve injury in the popliteal
space should be suspected in patients who have unrelenting posterior knee pain. In a case
report, Ekelund17 described idiopathic nerve entrapment in the popliteal space that caused
posterior knee pain in a young patient during walking and running. The patient had a tender
lateral popliteal space that was surgically explored, exposing a fibrous band that was
compressing the common peroneal nerve. Decompression was performed, and 2 weeks later,
the patient was asymptomatic. The same patient later returned to the clinic with complaints of
pain and had tenderness in the central aspect of the popliteal space in the opposite knee. This
area was also explored operatively, and fibers from the medial gastrocnemius were found to be
the cause of tibial nerve entrapment. This area was also decompressed, and in 2 weeks, the
patient was asymptomatic. In a case series, Saal et al18 also reported nine patients who had
tibial nerve lesions in the popliteal space with local tenderness over the area of entrapment.
Iatrogenic Injuries
Traumatic injuries or soft-tissue injuries that have been surgically repaired may provoke
posterior knee pain.
Postsurgical arthrofibrosis. Posterior knee pain can arise from posttraumatic arthrofibrosis,
a condition in which scar tissue proliferates after trauma. Occasionally, patients with a history
of injury or surgery may experience arthrofibrosis, and it usually produces limited range of
motion, stiffness, and pain. Affected patients experience posterior knee pain that becomes
worse with knee extension. A typical example may occur after an acute anterior cruciate
ligament (ACL)–deficient knee is reconstructed before the patient regains adequate range of
motion. In such cases, hypertrophic tissue may adhere to the ACL graft site or graft itself. This
additional scar tissue contributes to posterior knee pain, because it can prevent the patient
from regaining full range of motion postoperatively, particularly the terminal 5° of extension.19
Therefore, delaying the operation approximately 3 weeks after ACL injury should decrease the
likelihood of arthrofibrosis and reduce the overall incidence of posterior knee pain. Aggressive,
accelerated rehabilitation programs that emphasize passive extension, muscle reeducation,
cryotherapy, and functional rehabilitation may decrease the incidence of this disabling
condition.20
Bioabsorbable tacks. Another potentiator of postoperative posterior knee pain is placement
of bioabsorbable tacks. Because the menisci are important for weight bearing within the knee,
new systems of repair, such as bioabsorbable tacks, to prevent future degenerative joint
disease have been employed in arthroscopy. Bioabsorbable tacks are T-shaped fasteners with
barbed shafts. The tacks generally maintain structural integrity for approximately 4 to 6
months and fully resorb in 3 years. In one retrospective case series,21 a relatively high
incidence (31%) of focal posterior knee pain was referred from the site of tack placement,
despite a stable knee 6 weeks after surgery. However, pain resolved between 4 and 6 months
postoperatively, about the time the tacks begin to resorb. The tack length, number used, and
meniscal tear type were irrelevant to symptoms.
Knowledge of this transient phenomenon is important to the examiner evaluating patients who
have postarthroscopic posterior knee pain. Symptoms may include tenderness of the posterior
knee and sharp posterior knee pain that is exacerbated by knee extension. Physical therapy
protocols should not be altered, as there is no difference in knee stability or return to activity
in these patients. Reassurance is important during patient evaluation, since symptoms typically
resolve as the tacks resorb.
Thoughts About Diagnosis
With these descriptions and diagnostic tips (see table 1), examiners should have a more
comprehensive understanding of potential pain generators about the posterior knee. While
many different sources can cause posterior knee pain, review of potential causes should give
providers a firm understanding of disorders to consider in their diagnostic workup.
References
1. Baylis WJ, Rzonca EC: Common sports injuries to the knee. Clin Podiatr Med Surg 1988;5
(3):571-589
2. Kraag G, Thevathasan EM, Gordon DA, et al: The hemorrhagic crescent sign of acute
synovial rupture. Ann Intern Med 1976;85(4):477-478
3. Helfet AJ: Disorders of the Knee, ed 2. Philadelphia, Lippincott, 1982, p 478
4. Dienst M, Schneider G, Pahl S, et al: Intra-articular osteochondroma of the posterior
cavity of the knee. Arch Orthop Trauma Surg 2002;122(8):462-465
5. Ogata K, Ushijima M: Tenosynovial fibroma arising from the posterior cruciate ligament.
Clin Orthop 1987;215 (Feb):153-155
6. Muscolo DL, Makino A, Costa-Paz M, et al: Localized pigmented villonodular synovitis of
the posterior compartment of the knee: diagnosis with magnetic resonance imaging.
Arthroscopy 1995;11(4):482-485
7. Helms CA: Fundamentals of Skeletal Radiology, ed 2. Philadelphia, WB Saunders, 1995,
p 55
8. Clanton TO, Coupe KJ: Hamstring strains in athletes: diagnosis and treatment. J Am
Acad Orthop Surg 1998;6(4):237-248
9. Croisier JL, Forthomme B, Namurois MH, et al: Hamstring muscle strain recurrence and
strength performance disorders. Am J Sports Med 2002;30(2):199-203
10. Yang BY, Sartoris DJ, Resnick D, et al: Calcium pyrophosphate dihydrate crystal
deposition disease: frequency of tendon calcification about the knee. J Rheumatol
1996;23(5):883-888
11. Foldes K, Lenchik L, Jaovisidha S, et al: Association of gastrocnemius tendon
calcification with chondrocalcinosis of the knee. Skeletal Radiol 1996;25(7):621-624
12. Iguchi Y, Ihara N, Hijioka A, et al: Calcifying tendonitis of the gastrocnemius: a report of
three cases. J Bone Joint Surg Br 2002;84(3):431-432
13. LaPrade RF, Wentorf F: Diagnosis and treatment of posterolateral knee injuries. Clin
Orthop 2002;402(Sep):110-121
14. Veltri DM, Warren RF: Anatomy, biomechanics, and physical findings in posterolateral
knee instability. Clin Sports Med 1994;13(3):599-614
15. Akiyama K, Maeda T, Taniyasu N, et al: An unusual popliteal entrapment in a patient
with rheumatoid knee. J Cardiovasc Surg (Torino) 2001;42(2):281-284
16. Lambert AW, Wilkins DC: Popliteal artery entrapment syndrome. Br J Surg 1999;86
(11):1365-1370
17. Ekelund AL: Bilateral nerve entrapment in the popliteal space. Am J Sports Med 1990;18
(1):108
18. Saal JA, Dillingham MF, Gamburd RS, et al: The pseudoradicular syndrome: lower
extremity peripheral nerve entrapment masquerading as lumbar radiculopathy. Spine
1988;13(8):926-930
19. Shelbourne KD, Wilckens JH, Mollabashy A, et al: Arthrofibrosis in acute anterior
cruciate ligament reconstruction: the effect of timing of reconstruction and
rehabilitation. Am J Sports Med 1991;19(4):332-336
20. Shelbourne KD, Nitz P: Accelerated rehabilitation after anterior cruciate ligament
reconstruction. Am J Sports Med 1990;18(3):292-299
21. Whitman TL, Diduch DR: Transient posterior knee pain with the meniscal arrow.
Arthroscopy 1998;14(7):762-76
Dr Muché is a resident physician in the department of orthopedic surgery and rehabilitation,
division of physical medicine and rehabilitation, at Loyola University Medical Center in
Maywood, Illinois. Dr Lento is an attending physiatrist in the Rehabilitation Institute of Chicago
and assistant professor at Northwestern Medical School in Chicago. Address correspondence
to Julie A. Muché, MD, Dept of Orthopedic Surgery and Rehabilitation, 2160 S First Ave,
Maywood, IL 60153;e-mail to [email protected].
Disclosure information: Drs Muché and Lento disclose no significant relationship with any
manufacturer of any commercial product mentioned in this article. No drug is mentioned in this
article for an unlabeled use.
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Posterior Knee Pain and Its Causes

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