Knee Pain in Adults and Adolescents: The Initial Evaluation

Abstract

Knee pain affects approximately 25% of adults, and its prevalence has increased almost 65% over the past 20 years, accounting for nearly 4 million primary care visits annually. Initial evaluation should emphasize excluding urgent causes while considering the need for referral. Key aspects of the patient history include age; location, onset, duration, and quality of pain; associated mechanical or systemic symptoms; history of swelling; description of precipitating trauma; and pertinent medical or surgical history. Patients requiring urgent referral generally have severe pain, swelling, and instability or inability to bear weight in association with acute trauma or have signs of joint infection such as fever, swelling, erythema, and limited range of motion. A systematic approach to examination of the knee includes inspection, palpation, evaluation of range of motion and strength, neurovascular testing, and special (provocative) tests. Radiographic imaging should be reserved for chronic knee pain (more than six weeks) or acute traumatic pain in patients who meet specific evidence-based criteria. Musculoskeletal ultrasonography allows for detailed evaluation of effusions, cysts (e.g., Baker cyst), and superficial structures. Magnetic resonance imaging is rarely used for patients with emergent cases and should generally be an option only when surgery is considered or when a patient experiences persistent pain despite adequate conservative treatment. When the initial history and physical examination suggest but do not confirm a specific diagnosis, laboratory tests can be used as a confirmatory or diagnostic tool.

Full text

576 American Family Physician www.aafp.org/afp Volume 98, Number 9 ◆ November 1, 2018
Knee pain aects approximately 25% of adults. e prev-
alence of knee pain has increased almost 65% over the past
20 years, accounting for nearly 4 million primary care visits
annually.1,2 e initial evaluation should emphasize exclud-
ing urgent causes while considering the need for referral. A
standardized, comprehensive history and physical examina-
tion are crucial for dierentiating the diagnosis. Nonsurgi-
cal problems do not require immediate denitive diagnosis.
Imaging and laboratory studies can play a conrmatory or
diagnostic role when appropriate. is article reviews the
initial primary care oce evaluation of undierentiated
knee pain in adults and adolescents (ages 11 to 17 years),
highlighting key patient history and physical examination
ndings (Table 11,3-27). e uses of and indications for radi-
ography, musculoskeletal ultrasonography, magnetic reso-
nance imaging (MRI), and laboratory evaluation are also
addressed.
History
When evaluating knee pain, key aspects of the patient his-
tory include age; location, onset, duration, and quality of
pain; mechanical or systemic symptoms; history of swell-
ing; description of any precipitating trauma; and pertinent
previous medical or surgical procedures. Patients requiring
urgent referral generally have severe pain, immediate swell-
ing, and instability or inability to bear weight in association
with acute trauma, which suggests fracture, dislocation, or
tendon or ligamentous rupture. Referral is also indicated
for possible joint infection signs such as fever, swelling, and
erythema with limited range of motion.
PAIN LOCATION
Anterior. Isolated anterior knee pain suggests involve-
ment of the patella, patellar tendon, or its attachments.
Knee Pain in Adults and Adolescents:
The Initial Evaluation
Christopher W. Bunt, MD, Medical University of South Carolina, Charleston, South Carolina
Christopher E. Jonas, DO, and Jennifer G. Chang, MD, Uniformed Services University of the Health Sciences,
Bethesda, Maryland
Patient information: A handout on this topic is available at
https:// www.aafp.org/afp/2015/1115/p875-s1.html.
CME This clinical content conforms to AAFP criteria for
continuing medical education (CME). See CME Quiz on
page 569.
Author disclosure: No relevant financial aliations.
Knee pain aects approximately 25% of adults, and its prevalence has increased almost 65% over the past 20 years, account-
ing for nearly 4 million primary care visits annually. Initial evaluation should emphasize excluding urgent causes while
considering the need for referral. Key aspects of the patient history include age; location, onset, duration, and quality of pain;
associated mechanical or systemic symptoms; history of swelling; description of precipitating trauma; and pertinent med-
ical or surgical history. Patients requiring urgent referral generally have severe
pain, swelling, and instability or inability to bear weight in association with
acute trauma or have signs of joint infection such as fever, swelling, erythema,
and limited range of motion. A systematic approach to examination of the knee
includes inspection, palpation, evaluation of range of motion and strength, neu-
rovascular testing, and special (provocative) tests. Radiographic imaging should
be reserved for chronic knee pain (more than six weeks) or acute traumatic pain
in patients who meet specific evidence-based criteria. Musculoskeletal ultraso-
nography allows for detailed evaluation of eusions, cysts (e.g., Baker cyst), and
superficial structures. Magnetic resonance imaging is rarely used for patients
with emergent cases and should generally be an option only when surgery is
considered or when a patient experiences persistent pain despite adequate
conservative treatment. When the initial history and physical examination suggest but do not confirm a specific diagnosis,
laboratory tests can be used as a confirmatory or diagnostic tool. (Am Fam Physician. 2018; 98(9): 576-585. Copyright © 2018
American Academy of Family Physicians.)
Illustration by John Karapelou
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mercial us e of one individu al user of th e website. A ll other r ights reserve d. Contac t copyrights@a afp.org for copyrigh t questions and/or p ermis sion requ ests .

November 1, 2018 ◆ Volume 98, Number 9 www.aafp.org/afp American Family Physician 577
KNEE PAIN IN ADULTS AND ADOLESCENTS
Anterior knee pain that is
dull or aching and exacer-
bated by prolonged sitting
or climbing stairs is com-
mon in patellofemoral pain
syndrome.3 ,18 Athletes or
other adults with overuse
from running or jumping
sports can develop quadri-
ceps or patellar tendinop-
athy (commonly known
as jumper’s knee). Insidi-
ous onset of anterior knee
pain in adolescents during
rapid growth periods with
concomitant overuse sug-
gests Osgood-Schlatter dis-
ease (tibial apophysitis) or
Sinding-Larsen-Johansson
syndrome (distal patel-
lar apophysitis). Prepa-
tellar bursitis causes
patella-localized pain and
swelling and can occur
with isolated blunt trauma,
repetitive injury, or infec-
tion of the overlying skin.18
Medial or Lateral. Medial
or lateral knee pain with
corresponding joint-line ten-
derness can result from acute
injury or chronic overuse
and may indicate meniscal
derangement or a sprain or
rupture of a collateral liga-
ment.3,18 Pes anserine bursitis
is a common cause of medial
knee pain instigated by over-
use or blunt injury; the pain
is exacerbated by exion and
extension of the knee. Ado-
lescents experiencing medial
knee pain with or without
concurrent hip pain should
be evaluated for slipped
capital femoral epiphysis,
caused by a fracture through
the femoral physis (growth
plate).26 Chronic lateral knee
pain in runners or cyclists
(or stemming from other
TABLE 1
Selected Dierential Diagnosis of Knee Pain
Condition Historical points
Physical examination tests
and/or findings
Mechanical (acute)
Collateral ligament
sprain or rupture
(MCL, LCL)3-7
Medial or lateral pain
Injury from valgus (MCL) or varus
(LCL) force
Pain with applied force
Asymmetric gapping or laxit y
Associated internal derangements
Cruciate ligament
sprain or rupture
(ACL, PCL)3-6,8-13
ACL
Sudden pivoting injury
Audible pop
Instability
Eusion in 1 to 2 hours
PCL
Blunt trauma to anterior tibia
Sudden hyperflexion or exten-
sion injury
Pain with kneeling
ACL
Lachman test
Anterior drawer test
Pivot shift test
Loss of hyperextension
PCL
Posterior “sag” sign
“Quad activation”
Posterior drawer test
Medial plica
syndrome3-7
Acute (or chronic) medial pain
Overuse; onset of new activities
May report mechanical symptoms
(e.g., catching, clicking)
Tender mobile tissue band along
medial joint line
Meniscal tear 3, 5,6, 9-17 Male; age > 40 years
Cutting or t wisting injury while
bearing weight
Eusion in 24 to 48 hours
Locking or giving way
Thessaly test
McMurray test
Joint-line tenderness
Loss of extension (locked)
Patellar subluxation
or dislocation3-5,8
Anterior pain
Children or adolescents
History of subluxation
Apprehension
Laxity
Eusion
Mechanical (chronic)
Distal patellar
apophysitis (Sinding-
Larsen-Johannson
syndrome)8,18
Adolescents (10 to 13 years
of age)
Repetitive running, jumping,
or squatting
Tenderness of inferior pole of
patella
Local soft tissue swelling
Decreased flexibility of quadri-
ceps and hamstrings on aected
side
Iliotibial band
syndrome3-5,7
Lateral knee pain
Repetitive flexion
Runners, cyclists
Poor hamstring flexibility
Pain along entirety of iliotibial
band
Meniscal
derangement or
tear5, 6,9 -12, 14-17,1 9
Overuse
Medial or lateral pain
Advanced osteoarthritis
Thessaly test
McMurray test
continues
ACL = anterior cruciate ligament; LCL = lateral collateral ligament; MCL = medial collateral ligament;
PCL = posterior collateral ligament.
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578 American Family Physician www.aafp.org/afp Volume 98, Number 9 ◆ November 1, 2018
KNEE PAIN IN ADULTS AND ADOLESCENTS
activities involving repetitive
knee exion) is a common
presentation of iliotibial
band syndrome.3
Posterior. Isolated poste-
rior knee pain is less com-
mon but may occur from
a symptomatic popliteal
(Baker) cyst.3, 28 Posterior
knee pain aer acute trauma
raises suspicion for injury of
the posterior cruciate liga-
ment and posterior portions
of the meniscus, quadriceps
tendons, or neurovascular
structures.28 Chronic poste-
rior knee pain can suggest
hamstring tendinopathy.28
Diuse. Chronic, diuse
knee pain in adults older
than 50 years is commonly
attributable to degenerative
knee osteoarthritis, particu-
larly when the pain is worse
at the end of the day, is exac-
erbated by weight-bearing
activity, and is relieved by
rest.20 Acute onset of dif-
fuse atraumatic knee pain
(within hours or days) may
indicate an infectious eti-
ology, gout, or rheumatoid
arthritis; the latter is espe-
cially suspected when the
pain is bilateral or when it
occurs simultaneously in
other joints. In adolescents,
atraumatic or unexplained
diuse knee pain that wors-
ens with activity warrants
imaging to assess for osteo-
chondrosis8; similar pain
that persists at rest or that
worsens at night should raise
suspicion for malignancy.26
MECHANICAL SYMPTOMS
Mechanical symptoms,
such as locking, buckling,
or catching, suggest internal
derangement and possible
TABLE 1 (continued)
Selected Dierential Diagnosis of Knee Pain
Condition Historical points
Physical examination tests
and/or findings
Mechanical (chronic) (continued)
Osteoarthritis1,3-5,20-22 Diuse pain
Stiness when initiating movement
Exacerbated by bearing weight
Age > 50 years
Absence of trauma
Inflammatory signs
Pain worse at end of day
Chronic bony deformity
Leg asymmetry
Appreciable crepitus
Patellofemoral
pain syndrome
(chondromalacia
patellae)3,18,23-25
Anterior pain
Runners, cyclists
Patellar tilt test
Inhibition “shrug” test
“J” sign (abnormal tracking)
Poor vastus medialis oblique tone
Patellar grind
Pes anserine
bursitis3-7,18
Medial (or anteromedial) knee pain
Overuse
Tender nodule overlying antero-
medial proximal tibia
Quadriceps or
patellar tendinopathy
(jumper’s knee)3-5,8,18,26
Anterior pain
Athletes
Overuse and repetitive stress
Pain specific to the quadriceps or
patellar tendon
Tibial apophysitis
(Osgood-Schlatter
disease)4,8,18,26
Adolescents; associated with
growth spurt
Anterior pain; atraumatic
Tenderness at tibial tubercle
Inflammatory (noninfectious)
Crystal-induced
arthropathy (gout or
pseudogout)3,5,6,9,11,15,27
Acute, atraumatic, monoarticular
pain
Fever is possible
Older adults (> 60 years)
Risk factors for gout: male or post-
menopausal female, high intake of
purine-rich foods, critical illness,
specific medications
Risk factors for pseudogout:
hyperparathyroidism, hemo-
chromatosis, hypomagnesemia,
hypophosphatemia, osteoarthritis
Limited flexion/extension
Possible eusion and erythema
Arthrocentesis demonstrating
crystals on microscopy
Gout: negative birefringence
Pseudogout: positive
birefringence
Inflammatory (infectious)
Septic joint5,6,9,11,15 Acute/subacute
Systemic symptoms
Joint swelling, pain, erythema,
warmth, and joint immobility
Limited flexion/extension
Eusion and erythema
Arthrocentesis with Gram stain
and culture
Elevated white blood cell count,
erythrocyte sedimentation rate,
and C-reactive protein
Informati on from references 1 and 3 throu gh 27.

November 1, 2018 ◆ Volume 98, Number 9 www.aafp.org/afp American Family Physician 579
instability but can also occur in medial plica syndrome18
(Table 11,3-27). A popping sensation at the time of injury
may occur in meniscal or ligamentous tears. A knee that is
“locked” in exion and that cannot be extended should be
examined for a meniscal tear.4,14,15
SWELLING
If the patient has an acute injury, a knee joint eusion
strongly suggests internal derangement.14, 26 Swelling that
occurs immediately (minutes to a few hours) aer injury
suggests a ligament rupture, intra-articular fracture, or
patellar dislocation; swelling that appears within hours to
a few days suggests a meniscal tear.15,19 Atraumatic swelling
with erythema or palpable warmth implies gout or pseudo-
gout, arthritic are, or infection. Swelling that is limited to
the borders of the patella suggests prepatellar bursitis.4,14,15
MECHANISM OF INJURY
When determining the mechanism of injury, gather infor-
mation about pain onset, positioning of the knee during
and aer the injury, and subsequent weight-bearing status
(Table 11,3-27). Meniscal tears commonly result from twist-
ing injuries in the weight-bearing knee. Ligamentous rup-
ture may result from excess deceleration force applied to a
weight-bearing, xed, lower extremity or a direct blow to
the lateral or medial knee. A fracture should be considered
when patients are unable to walk or limp at least four steps
both immediately aer injury and at rst presentation.9,29, 30
MEDICAL OR SURGICAL HISTORY
Family physicians should ask patients about previous knee
or other joint pain, injuries, or surgeries. Physicians should
also inquire about systemic medical conditions (e.g., autoim-
mune or infectious diseases, sexua lly transmitted infect ions)
and review family history of autoimmune and degenera-
tive conditions. Personal history of knee injury or surgery
and family history of knee osteoarthritis or joint replace-
ment are established risk factors for knee osteoarthritis.20, 21
Additional risk factors for knee osteoarthritis include age
older than 50 years, female gender, and being overweight.20
Physical Examination
A systematic approach to examination of the knee includes
inspection, palpation, range of motion and strength evalua-
tion, neurovascu lar assessment, and specia l (provocative) tests.
INSPECTION
Erythema, swelling, bruising, lacerations, gross deformity,
discoloration, and any asymmetry of bony or so tissue
landmarks, including atrophy and valgus or varus deformi-
ties, should be noted.
PALPATION
Palpation should assess for pain over all bony and so tissue
landmarks (Figure 131), warmth, and eusion. Pes anserine
FIGURE 1
Anterior view of the osseous, ligamentous, and fibro-
cartilaginous structures of the knee.
Illustration by Christy Krames
Reprinted with perm ission from Tandeter HB, Shvartzman P, Ste-
vens MA. Acute knee in juries: use of d ecision ru les for selective
radiograph ordering. Am Fam Physician. 1999; 60(9): 2600.
BEST PRACTICES IN FAMILY MEDICINE
Recommendations from the Choosing
Wisely Campaign
Recommendation
Sponsoring
organization
Avoid ordering knee magnetic resonance
imaging for a patient with anterior knee
pain without mechanical symptoms
or eusion unless the patient has not
improved after completion of an appro-
priate functional rehabilitation program.
American Med-
ical Society for
Sports Medicine
Source: For more info rmation on the Choosing Wise ly Campa ign,
see https:// choosingwisely.org. For sup porting citati ons and to
search Choosing Wise ly recomme ndations relevant to p rimar y
care, see https:// www.aafp.org/afp/recommendations/search.htm.
Anterior
cruciate
ligament
Distal
femoral
condyle
Patellofemoral
groove
Posterior
cruciate
ligament
Lateral
meniscus
Tibial
collateral
ligament
Fibular
collateral
ligament
Medial
meniscus
Tibial
plateau
Tibia
Fibula
Patella
(reflected)

580 American Family Physician www.aafp.org/afp Volume 98, Number 9 ◆ November 1, 2018
KNEE PAIN IN ADULTS AND ADOLESCENTS
bursitis manifests as a tender nodule over the medial proxi-
mal tibia approximately 3 cm distal to the joint line, while a
plica can be appreciated as a thin band of tissue most com-
monly near or overlying the medial joint line. A joint that
is as warm or warmer than the tissue above or below that
joint indicates infection or inammation. An evaluation
for eusion with the ballottement test and “milking” of the
suprapatellar pouch should be conducted with the patient
supine with the injured knee in extension.3
RANGE OF MOTION AND STRENGTH TEST
Range of motion (active and then passive) and strength
testing (graded 0 to 5) should be used to assess exion and
extension of the k nee. Normal limits of k nee range of motion
include extension from 0 to –10° and
exion to 135°.5 e examiner should
assess for a lateral patellar tracking
(“J” sign) vs. normal patellofemoral
tracking during the range of motion
examination23,24,32,33 (see gure at
https:// www.aafp.org/afp/2007/0115/
p194.html#afp20070115p194-f2).
NEUROVASCULAR ASSESSMENT
Neurovascular examination of the knee
includes assessment of sensation to light
touch; deep tendon reexes (graded 0 to
4+) of the patellar and Achilles tendons;
and bilateral palpation of the popli-
teal, dorsalis pedis, and posterior tibial
pulses (graded 0 to 4+).10
SPECIAL PROVOCATIVE TESTS
Special (provocative) tests are used to
bilaterally assess specic structures
of the knee; these tests vary in their
accuracy (Table 25,11). Pain and eu-
sion may limit the usefulness of these
tests in the acute setting, requiring
repeat testing or deferment until eu-
sion has subsided.11
Patellar Apprehension Test. is test
involves laterally shiing the patella
and is a variant of the patellar mobil-
ity test; both of these tests evaluate
for patellar subluxation6 (see gure at
https: // www.aafp.org/afp/200 7/0115/
p194.html#afp2 0 070115p194-f3).
Patellar tilt and patellar grind (or inhi-
bition) testing (see gure at https://
ww w.aaf p.org/afp/2007/0115/p194.
html#afp20070115p194-f5) can indicate patellofemoral pain
syndrome, as can assessment of core stability while the
patient completes a single leg squat.
Lachman, Anterior Drawer, and Pivot Shi Tests. ese
tests evaluate for anterior cruciate ligament (ACL) injury
(Table 25,11 and Table 34,6,11,34). e Lachman test is the
most commonly used technique for assessing the ACL6,7
(Figure 26).
Gravity “Sag” Sign Near Extension, Active Reduction
“Quad Activation” of Posterior Tibial Subluxation, and Pos-
terior Drawer Tests. ese tests evaluate for posterior collat-
eral liga ment (PCL) injury6,34 (Table 34,6,11,34). In one study, the
sag sign correctly diagnosed PCL injury in 20 of 24 patients,
and “quad activation” correctly identied PCL injury in 18
TABLE 2
Knee Injury: Diagnostic Accuracy of Physical Examination
Maneuvers and Clinical Findings
Maneuver or clinical
findings
Positive
likelihood
ratio*
Negative
likelihood
ratio*
Probability of injury if
maneuver is†
Positive (%) Negative (%)
Anterior cruciate liga-
ment tear
Pivot shift test 20.3 0.4 69 4
Lachman test 12.4 0.14 58 2
Anterior drawer test 3.7 0.6 29 6
Eusion
Ballottement test; notice-
able swelling
3.6 0.4 NA NA
Meniscal tear
Thessaly test 39.3 0.09 81 1
McMurray test 1 7. 3 0.5 66 5
Age > 40, continuation of
activit y not possible, weight
bearing during trauma, and
pain with passive flexion5
5.8 0.9 39 9
Joint-line tenderness 1.1 0.8 11 8
NA = not app licable.
*—The likelihood ratio is a measure of how well a positive test r ules in dis ease or a negative
test rules out disease.
†—Based on an overall likelih ood of 10% for ea ch injur y. If clinica l suspicion is higher or lower,
the proba bility would be correspondingly higher or lower.
Adapted with permission from Grover M. Evaluati ng acutely in jured pati ents for inte rnal
derangement of the knee. Am Fam Physician. 2012; 85(3): 250, with additional information
from reference 5 .

November 1, 2018 ◆ Volume 98, Number 9 www.aafp.org/afp American Family Physician 581
KNEE PAIN IN ADULTS AND ADOLESCENTS
of 24 patients35 (see gure
at https:// www.aafp.org/
afp/1999/1201/p2599.html
#afp19991201p2599-f12).
essaly and McMur-
ray Tests. e essaly test
(Figure 311) is preferred over
the McMurray test (see g-
ure at https:// www.aafp.
org/afp/2003/0901/p907.
html#afp20030901p907-f5)
during the initial evalua-
tion for meniscal injury;
however, the eectiveness
of both tests is oen limited
because of the patient’s pain
and inability to fully bear
weight. A positive McMur-
ray test (reported pain plus
palpable click or clunk)
substantially increases the
probability of a meniscal
tear because this test has
high specicity (97%) but
low sensitivity (52%).7,12,16,17
Valgus and Varus Stress
Tests . No systematic review
has addressed the diag-
nostic accuracy of physi-
cal examination ndings
in patients with medial or
lateral collateral ligament
injuries. e most common
types of physical exam-
ination tests for assessing
these injuries are the val-
gus and varus stress tests.
Asymmetric gapping or
laxity is suggestive of this
injury6,11,20,34 (Figure 46).
Imaging
RADIOGRAPHY
Although a comprehensive
history and physical exam-
ination are the mainstays of
the initial evaluation, radi-
ography may be necessary
to further evaluate undif-
ferentiated knee pain. How-
ever, with a 2% prevalence
TABLE 3
Physical Examination Maneuvers for the Knee
Tes t Description
Anterior cruciate ligament tear
Anterior drawer
test*
With the patient supine on the examining table, flex the hip to 45° and the
knee to 90°. Sit on the dorsum of the foot, wrap hands around the ham-
strings (ensuring that these muscles are relaxed), then pull and push the
proximal par t of the leg, testing the movement of the tibia on the femur. Do
these maneuvers in three positions of tibial rotation: neutral, 30° externally
rotated, and 30° internally rotated. A normal test result is no more than 6 to
8 mm of laxity.
Lachman test* With the patient supine on the examining table and the leg slightly externally
rotated and flexed (20 to 30°) at the examiner’s side, stabilize the femur with
one hand and apply pressure to the back of the knee with the other hand,
with the thumb on the joint line. A positive test result is movement of the
knee with a soft or mushy end point.
Pivot shift test* Fully extend the knee and rotate the foot internally. Apply a valgus (abduction)
force while progressively flexing the knee, watching and feeling for translation
of the tibia on the femur.
Posterior cruciate ligament tear
Posterior drawer
test
The patient should be supine on the examining table with knees flexed to
90°. While standing at the side of the examination table, the physician looks
for posterior displacement of the tibia (posterior “sag” sign).4,6,34 The physi-
cian then fixes the patient ’s foot in neutral rotation (by sitting on the foot),
positions thumbs at the tibial tubercle, and places fingers at the posterior
calf. The physician then pushes posteriorly and assesses for posterior dis-
placement of the tibia.
Gravity “sag”
sign near ex ten-
sion test
In a resting position with the distal femur on a 15-cm support and the heel
resting on the examination table (20° of flexion), the unsuppor ted proximal
tibia displays a concave anterior contour.
Active reduction
“quad activation”
of posterior tibial
subluxation
When the patient raises the heel 2 to 3 cm, a normal anterior contour is
restored.
Meniscal tear
Joint-line
tenderness
Palpate medially or laterally along the knee to the joint line bet ween the
femur and tibial condyles. Pain on palpation is a positive finding.
McMurray test† Flex the hip and knee maximally. Apply a valgus (abduction) force to the knee
while externally rotating the foot and passively extending the knee. An audible
or palpable snap or click with pain during extension suggests a tear of the
medial meniscus. For the lateral meniscus, apply a varus (adduction) stress
during internal rotation of the foot and passive extension of the knee.
Thessaly test‡ Hold patient ’s outstretched hands while the patient stands fl at footed on the
floor, internally and externally rotating the aected leg three times with the
knee flexed 20°. The unaected leg should be flexed to avoid contact with the
floor. Patient-repor ted pain at the medial or lateral joint line is a positive finding.
Eusion
Ballottement
test§
Push the patella posteriorly with two or three fingers using a quick, sharp
motion. In the presence of a large eusion, the patella descends to the troch-
lea, strikes it with a distinct impact, and flows back to its former position.
*—See procedures bei ng performed at https:// www.aafp.org/afp/videos.
†—See test being per formed at http:// www.youtube.com/watch?v=ohSzjNj-KCA&NR=1.
‡—See test being per formed at http:// www.youtube.com/watch?v=R3oXDvagnic.
§—See tes t being perform ed at http:// www.youtube.com/watch?NR=1&v=oULBAyfwkaE.
Adapted with permis sion from Grover M. Evaluating acutely in jured patients for inte rnal derangement of the
knee. Am Fam Physician. 2012; 85( 3): 249, with additional information f rom references 4 , 6, and 34 .

582 American Family Physician www.aafp.org/afp Volume 98, Number 9 ◆ November 1, 2018
KNEE PAIN IN ADULTS AND ADOLESCENTS
of fractures in outpatient primary care settings and a low
diagnostic yield for clinically signicant fractures, radi-
ography should be reserved for chronic knee pain of more
than six weeks duration or acute traumatic pain in patients
who meet specic evidence-based criteria.11,3 6
e American College of Radiology Appropriateness
criteria, the Ottawa Knee Rule (https:// www.mdcalc.com/
ottawa-knee-rule), and the Pittsburgh Knee Rule (https://
www.mdcalc.com/pittsburgh-knee-rules) provide support
for imaging decisions. e Ottawa Knee Rule is a vali-
dated tool (98.5% to 100% sensitivity, 49% specicity) that
decreases unnecessary radiography by 28% to 35% in the
patient with an acutely injured knee.11,29,31,37- 40 A prospective
validation trial comparing the Ottawa Knee Rule and the
Pittsburgh Knee Rule showed that each rule is useful, but
the Pittsburgh rule appears to be more sensitive. Speci-
cally, the Ottawa rule had a sensitivity of 97% (95% con-
dence interval [CI], 90% to 99%) and specicity of 27% (95%
CI, 23% to 30%), whereas the Pittsburgh Knee Rule yielded
a sensitivity of 99% (95% CI, 94% to 100%) and specicity of
60% (95% CI, 56% to 64%)30 (Table 411).
e three recommended radiographic views are antero-
posterior view, lateral view, and Merchant’s view (for the
patellofemoral joint).30,40 Oblique views can assess for tibial
plateau fractures, and the notch or tunnel (intracondylar)
view can visualize osteochondral lesions.4 If osteoarthritis is
suspected, weight-bearing radiographs should be obtained
to assess for joint-space narrowing, subchondral sclerosis,
osteophytes, and bony cysts.4,22
ULTRASONOGRAPHY
Musculoskeletal ultrasonography performed by a trained
clinician13,25,41,42 allows for limited evaluation of eusions,
cysts (e.g., Baker) and supercial tendons, collateral lig-
aments, muscles, vasculature, and nerves. In particular,
dynamic evaluation of the extensor mechanism (quadriceps
tendon, patella, and patellar tendon) can be readily assessed.
Mechanical complaints such as snapping, clicking, or pop-
ping can be evaluated through palpation with an ultrasound
transducer.40
FIGURE 2
Lachman test.
Illustration by Steve O h
Reprinted with perm ission from Smith BW, Green G A. Acute knee
injuries. Part I: history and physical examination. Am Fam Physician.
1995; 51(3): 618.
FIGURE 3
Thessaly test. Physician should hold the patient’s out-
stretched hands while the patient stands flat footed
on the floor, with knee at 20° of flexion, and inter-
nally and externally rotates the knee three times. The
other knee is flexed to avoid contact with the floor.
Patient-reported pain at the medial or lateral joint line
is a positive finding.
Illustration by Marcia Hart sock
Reprinted with perm ission from G rover M. Evaluating acutel y
injured patients for internal de rangem ent of the knee. Am Fam Phy-
sician. 2012; 85(3): 251.

November 1, 2018 ◆ Volume 98, Number 9 www.aafp.org/afp American Family Physician 583
KNEE PAIN IN ADULTS AND ADOLESCENTS
MRI
Emergent MRI is rarely indicated and
is typically reserved for potential sur-
gical indications such as dislocation,
ACL or PCL tear, fracture not visible
on radiography, vertical meniscal tear,
malignancy, vascular injury, or osteo-
myelitis. Ideally, MRI will conrm the
ndings from the history and physical
examination. MRI also may be useful if
mechanica l symptoms (such as locking,
painful clicking, or inability to fully
extend the knee) occur or if recurrent
swelling or persistent pain is present
aer a trial of adequate conservative
treatment. e American College of
Radiolog y has established Appropriate-
ness Criteria for ordering knee MRI.43
Laboratory Examination
When the initial history and physical
examination suggest but do not con-
rm a specic diagnosis, laboratory
examination can play a conrma-
tory or diagnostic role. is workup
could include serology for suspected
inammatory conditions (erythrocyte
TABLE 4
Indications for Radiography in Patients with Acute
Knee Injury
Indication ACR Criteria
Ottawa
Knee Rule
Pittsburgh
Knee Rule
Age < 12 or > 50 years X
Age ≥ 55 years X
Altered mental status X
Fall or blunt trauma X
Inabilit y to bear weight for four
steps (unable to transfer weight
twice) immediately after injury
or in the emergency set ting
X X X
Inabilit y to flex knee to 90 ° X X
Joint eusion within 24 hours
of a direct blow or fall
X
Tenderness over head of fibula
or isolated to patella without
other bony tenderness
X X
ACR = American College of Radiology.
Adapted with permission from Grover M. Evaluati ng acutely in jured pati ents for inte rnal
derangement of the knee. Am Fam Physician. 2012; 85(3): 248.
FIGURE 4
Varus and valgus stress test. The maneuvers should be performed with the knee in neutral full extension and at
30° of flexion.
Illustration by Steve O h
Reprinted with perm ission from Smith BW, Green G A. Acute knee injuries. Par t I: h istory and physical examinati on. Am Fam Physician. 1995; 51(3): 617.
Varus stress test Valgus stress test
0°
30°
0°
30°

584 American Family Physician www.aafp.org/afp Volume 98, Number 9 ◆ November 1, 2018
KNEE PAIN IN ADULTS AND ADOLESCENTS
sedimentation rate or C-reactive protein and complete blood
count when infection is suspected), autoimmune conditions
(rheumatoid factor or auto-antibodies [antineutrophil anti-
bodies]), or microscopic examination of arthrocentesis uid
for gouty crystals or evidence of bacterial infection.3, 27, 3 4, 4 4
Data Sources: A PubMed search was completed using Clinical
Queries and the search terms knee pain, evaluation, history,
examination, radiographic imaging, laboratory, diagnosis, eu-
sion, gout, and pseudogout. The search included meta-analyses,
randomized controlled trials, clinical trials, and reviews. Also
searched were the Agency for Healthcare Research and Quality
evidence reports, Essential Evidence Plus, Clinical Evidence,
the Cochrane database, Google Scholar, the National Guide-
line Clearinghouse database, the TRIP database, and UpToDate.
Search dates: July, October, and November 2017; July 2018.
The authors thank Ms. Rhonda Allard, who was invaluable during
the literature search.
The opinions and assertions contained herein are the private
views of the authors and are not to be construed as ocial or as
reflecting the views of the Department of Defense, the U.S. Air
Force Medical Service, the Uniformed Services University of the
Health Sciences, or the U.S. Air Force at large.
This article updates previous articles on this topic by Calmbach
and Hutchens, Part I44 and Part II.3
The Authors
CHRISTOPHER W. BUNT, MD, FAAFP, is the assistant dean for
Student Aairs and an associate professor in the Department
of Family Medicine at the Medical Universit y of South Caro-
lina, Charleston, SC. He is also an associate professor in the
Department of Family Medicine at the Uniformed Services
Universit y of the Health Sciences, Bethesda, Md.
CHRISTOPHER E. JONAS, DO, FAAFP, CAQSM, is an assistant
professor in the Department of Family Medicine at the Uni-
formed Ser vices University of the Health Sciences.
JENNIFER G. CHANG, MD, is an assistant professor in the
Department of Family Medicine at the Uniformed Services
Universit y of the Health Sciences.
Address correspondence to Christopher W. Bunt, MD, FAAFP,
Medical University of South Carolina, 96 Jonathan Lucas St.,
Ste. 601, MSC 617, Charleston, SC 20814 (e-mail: buntc@
musc.edu). Reprints are not available from the authors.
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Clinical recommendation
Evidence
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C 3, 4, 6, 7, 11, 12,
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