Knee Pain in Primary Care: Utility of the Physical Exam in Guiding Diagnosis
Jennifer Leahy, MD
Musculoskeletal Rotation
January 2005
Introduction
Knee pain is a common symptom among patients presenting to primary care providers. By one
estimate, in 1999 there were 3.7 million visits to primary care providers for knee pain1. Six
percent of patients presenting to a primary care provider with a physical symptom had knee
pain1. Another study done in the United Kingdom showed that for adults over the age of 50,
roughly half of almost 6500 patients surveyed reported knee pain sometime during a 12-month
period. Of these, 33% consulted their general practitioner about their symptoms2.
The differential diagnosis for knee pain is broad. However, in the primary care setting, the
provider is often faced with addressing multiple different issues with a patient within a timelimited visit. Therefore an efficient strategy for categorizing and triaging different types of knee
problems helps ensure that specialist referrals are made in a timely fashion when necessary, and
that appropriate treatments are initiated to improve the patient’s symptoms. Unlike orthopedic
offices or sports medicine clinics, the primary care provider often may not have access to
imaging modalities on-site, so the main tools readily available are simply the history and
physical exam.
The objective of this discussion is to outline the physical exam of the knee, and to review the
evidence for the utility of certain physical exam findings or maneuvers in helping to diagnose
specific causes of knee pain.
Differential Diagnosis of Knee Pain
There are many potential causes of knee pain, including pathology arising in the joint itself or in
structures surrounding the joint. Both inflammatory and mechanical processes can cause knee
pain, and can be the result of traumatic injury to the knee or of degeneration over time. There are
multiple structures in and around the knee which can be damaged and cause pain, including
bones, cartilaginous structures, ligaments, tendons, bursae, and muscles. Structures distant to the
joint can also refer pain to the knee. The number of distinct entities which can cause knee pain is
large, as shown in Table 1. However, a relatively small number of these make up most of the
cases seen in primary care. Table 2 lists the most common causes of acute knee pain based on
data from the National Ambulatory Medical Care Survey1. One notable omission from this list is
patellofemoral syndrome, which is a common cause of chronic knee pain and is the leading cause
of knee pain in patients under age 453. This discussion will concentrate on using the physical
exam to differentiate between these more common causes.
1
Table 1: Differential Diagnosis of Knee Pain
Articular Pathology
Inflammatory Processes
Rheumatoid arthritis
Spondyloarthropathies
Gout
Pseudogout
Septic arthritis
Degenerative Processes
Osteoarthritis
Meniscal tear
Patellofemoral syndrome
Traumatic Processes
Bony fractures
Cruciate ligament injuries
Meniscal injuries
Periarticular Pathology
Collateral ligament injuries
Tendonitis
Patellar tendonitis
Iliotibial band tendonitis
Bursitis
Prepatellar bursitis
Pes anserine bursitis
Table 2: Most Common Causes of Acute Knee Pain in Primary Care1
Osteoarthritis (34%)
Meniscal injury (9%)
Collateral ligament injury (7%)
Cruciate ligament injury (4%)
Gout (2%)
Fracture (1.2%)
Undifferentiated causes including sprains and strains (42%)
Physical Exam Overview
A complete physical exam of the knee involves inspection of the knee and observation of the
ability to perform basic functions, palpation of structures in and around the knee, assessment of
the range of motion of the knee joint, assessment of strength of the muscles supporting the joint,
and performance of a variety of provocative maneuvers designed to reveal specific defects by
eliciting pain or instability with certain movements.
Inspection/Observation
With the patient standing, initial inspection may reveal obvious erythema or swelling as
evidenced by loss of the normal peripatellar dimples. The quadriceps muscles should be
inspected for evidence of atrophy. The stance should be assessed, looking for varus or valgus
deformity which can alter the stresses on the knee joint. Similarly, inspection of the feet can
reveal pes planus or pes cavus which can predispose to certain conditions such as patellofemoral
2
syndrome or jumper’s knee4. In females, increased Q-angle (defined as the angle between a line
connecting the anterior superior iliac spine to the center of the patella and a line from the center
of the patella through the tibial tubercle) can also raise suspicion for patellofemoral syndrome5.
The patient should be asked to walk, observing the gait for signs of pain or abnormal hip motion.
Depending on the severity and acuity of pain, the patient can also be asked to squat and/or “duck
waddle”, which can quickly rule out significant pathology, since these motions require intact
collateral and cruciate ligaments and menisci, and lack of significant effusion or arthritis6.
Palpation
With the patient seated, the joint line is easiest to identify and should be palpated along its length
for focal tenderness suggestive of intra-articular pathology. The medial and lateral aspects of the
knee over the collateral ligaments can also be palpated for tenderness. The tibial tubercle and the
midline of the medial tibial plateau are other focal areas which should be assessed for tenderness
if iliotibial band disease or pes anserine bursitis are suspected, respectively. Diffuse tenderness is
more indicative of an arthritis than injury to one specific structure.
While still seated, the knee can be ranged through flexion and extension with one hand over the
joint to feel for crepitus or any unusual sensation such as clicking or popping.
The patient should then be asked to lie supine in order to relax the quadriceps musculature. This
is the easiest position in which to assess for effusion. Milking any fluid laterally and then
compressing the lateral aspect may produce a “bubble” or “wave” sign as fluid is pushed back to
the medial side6, 7. This may reveal a smaller effusion than the “ballottement” sign, in which the
patella is compressed and feels as if it is floating on a layer of fluid. This usually is felt if there is
10-15 cc of fluid within the joint. With larger effusions still (approximately 20-30 cc), the
suprapatellar space will become filled and the knee will lose its normal contours6. The knee
should also be felt for warmth, which usually indicates inflammation especially with crystalline
arthritis and infection.
The patella is also best evaluated with the patient supine. It should be assessed for transverse
mobility, and when deviated laterally or medially the underside can be palpated for tenderness
indicative of patellofemoral disease4.
Range of Motion
This is usually best done with the patient sitting. Passive range of motion should be assessed
from full extension (zero degrees) to full flexion (approximately 130 degrees). The “heel-tobuttock distance” can also be used to quantify degree of flexion if desired. Patellar tracking
should be observed as the knee ranges through flexion and extension; the “J-sign” is seen if the
patella shifts medially with flexion and is a sign of abnormal lateral tracking8.
Strength
Quadriceps strength should be assessed by asking the patient to extend the leg against resistance.
It is usually intact unless significant knee pain has been present long enough to cause atrophy, or
there is a patellar tendon injury, patellar fracture, advanced arthritis, or a large effusion6.
3
Provocative Maneuvers
There are many specific tests used to try to identify specific pathology within the knee. The more
commonly used or useful ones are as follows:
To assess damage to medial or lateral collateral ligaments:
Varus/Valgus stress test: Knee is flexed to 30 degrees, then varus and valgus stresses are
applied. A positive test is pain, and/or loss of a firm stop. It is important to do this
test in 30 degrees of flexion, as in full extension much of the stress is taken up by the
capsule itself. 9
Apley distraction test: Patient lies prone and the knee is flexed to 90 degrees. The femur
is stabilized against the table and the foot is pulled upward and internally and
externally rotated. A positive test is pain with this maneuver. 9
To assess damage to anterior cruciate ligament:
Lachman’s test: Knee is flexed ~30 degrees, the femur is grasped with one hand, then the
tibia is grasped with the other hand and pulled anteriorly. A positive test is excessive
movement compared to the opposite knee, and/or lack of a firm endpoint. It is
important for the patient to fully relax the quadriceps during this maneuver. 9
Anterior drawer test: Knee is flexed to ~90 degrees, and the foot is stabilized with the
examiner’s body. The tibia is then grasped with both hands and pulled anteriorly. A
positive test is pain, excessive movement relative to the opposite side, and/or lack of
a firm endpoint.6, 9.
Pivot-shift or MacIntosh test: The lower leg is extended and supported by the examiner.
The knee is then slowly flexed while applying valgus stress and internally rotating. A
positive test is visible anterior movement of the tibia in relation to the femur during
the initial 30 degrees of flexion. 8
To assess meniscal integrity:
McMurray’s test: Knee is flexed to 90 degrees. One hand is used to hold the knee along
the joint line and the other cradles the foot. The knee is passively ranged through
flexion and extension while applying internal and external rotation to the foot. A
positive test is pain or a palpable click on internal rotation (medial meniscus) or
external rotation (lateral meniscus).5, 8, 9
Apley grind test: Patient lies prone and the knee is flexed to 90 degrees. The femur is
stabilized against the table and then downward pressure is applied to the foot and
ankle while internally and externally rotating. A positive test is pain with this
maneuver. 9
Bounce-home test: Knee is flexed to 30 degrees, then allowed to extend passively while
the examiner supports the lower extremity. A positive test is pain with this
maneuver. 8
To assess for patellar pathology:
Patellar grind test: Patient lies supine and downward pressure is applied to the patella
while moving in transverse and then longitudinal direction. A positive test is pain
and or crepitation. 8
4
Patellar apprehension test: The patella is displaced laterally. Positive test is pain or a
“give-way” sensation. 5
Clark’s sign or Install’s maneuver: Patient lies supine and the patella is fixed by applying
inferiorly-directed pressure at the superior pole. The patient is then instructed to
contract the quadriceps muscle. A positive test is pain with the maneuver.8
To assess for shortening of the iliotibial band:
Ober’s test: Patient lies in a lateral decubitus position with the knees slightly flexed. The
top leg is then extended at the hip such that the shoulder, hip, and knee are aligned,
and the knee flexed to 90 degrees. The examiner then gently releases the top leg and
allows it to fall toward the table. A positive test is failure of the upper knee to touch
the examination table.4, 8
Figure 1: Examination Maneuvers for Evaluating Anterior Cruciate Ligament and Menisci (from Solomon D,
Simel D, et al7)
Right knee shown. Examination maneuvers include the Lachman, anterior drawer, lateral pivot shift, Apley
compression, and McMurray tests. Lachman test, performed to detect anterior cruciate ligament (ACL)
injuries, is conducted with the patient supine and the knee flexed to 20° to 30°. The anterior drawer test
detects ACL injuries and is performed with the patient supine and the knee in 90° of flexion. The lateral
pivot shift test is performed with the patient supine, the hip flexed 45°, and the knee in full extension.
Internal rotation is applied to the tibia while the knee is flexed to 40° under a valgus stress (pushing the
outside of the knee medially). The Apley compression test, used to assess meniscal integrity, is performed
with the patient prone and the examiner's knee over the patient's posterior thigh. The tibia is externally
rotated while a downward compressive force is applied over the tibia. The McMurray test, used to assess
meniscal integrity, is performed with the patient supine and the examiner standing on the side of the
affected knee. See "Function" section of text for full explanation of all examinations.
5
Sensitivity and Specificity of Physical Exam in Diagnosing Particular Conditions
Given this multitude of physical exam signs and maneuvers for various knee problems, the
primary care provider will of course want to know which findings are the most useful in
differentiating particular conditions. A brief review of the literature shows that relatively few of
these signs and maneuvers have been studied in detail. The studies which have been done are
also somewhat limited, in that most of them analyzed the maneuvers in the hands of specialists
(orthopedists, sports medicine physicians, and/or rheumatologists), and the maneuvers
themselves were not always standardized. With the exception of one study looking at interobserver reliability of physical exam findings in osteoarthritis, none of the studies assessed interexaminer reproducibility of results1, 10, 11. Therefore the results discussed below may not be
completely applicable to primary care physicians. The data for maneuvers which have been best
studied are presented below.
Anterior cruciate ligament tears
One review done by Jackson et al in 2003 analyzed 35 studies comparing knee examination
findings with arthroscopy or arthrotomy1. The Lachman test was found to be the most sensitive
for detecting ACL tear, with a sensitivity of 87%, and also had good specificity of 93%.
However, the pivot-shift test was found to be slightly more specific (97%)1. The anterior drawer
test was found to be inferior to both the Lachman and pivot tests with a sensitivity of 48% and
specificity of 87%1, 7.
Meniscal tear or injury
The same review by Jackson also looked at utility of tests for meniscal injury. The presence of
focal joint line tenderness was found to be relatively sensitive (76%) but not specific (29%),
whereas a positive McMurray test was specific (97%) but not sensitive (52%)1, 7. However,
another study estimated the specificity of the McMurray test at only 59%6, 7, 8. The study by
Jackson concluded that a negative physical exam could reliably exclude significant meniscal
pathology1. A review of the evidence by Ellis and Meadows10 came to the same conclusion.
However, they concluded that no clinical exam test could effectively rule in meniscal
pathology10.
Patellofemoral syndrome
There was little data about the utility of tests for patellofemoral syndrome. One study of 85
patients found that neither the patellar grind test nor Clark’s sign exceeded 70% sensitivity or
specificity8. Further study is needed.
Osteoarthritis
The American College of Rheumatology has established clinical criteria for the diagnosis of
osteoarthritis which include the physical exam findings of crepitus, bony tenderness, bony
enlargement, and absence of palpable warmth. Other clinical characteristics making up the
criteria are historical features, namely age >50 years and stiffness lasting less than 30 minutes.
The presence of at least three of these characteristics is 95% sensitive and 69% specific for a
diagnosis of osteoarthritis1. Jackson’s study estimates that the positive predictive value of the
presence of 3 clinical characteristics is 62%1. However, these findings are broadly defined,
raising the question of how reliably the presence of these criteria can be detected. A study done
6
to assess the reliability of these findings among rheumatologists found that all except for warmth
were reliable11. However, the reliability of these findings by primary care physicians is less clear.
Fracture
In a patient with acute knee pain following an injury, fracture must also be considered. There
have been multiple algorithms developed to predict the likelihood of fracture based on specific
clinical features, helping the clinician decide whether x-ray imaging is necessary. The review
done by Jackson looked at 5 studies of 4 different prediction rules and concluded that the
“Ottawa knee rules” are the best validated. These rules state that x-rays should be obtained if the
patient is over age 55 (regardless of physical exam findings), or if any of the following are
present: tenderness to palpation at the head of the fibula, isolated tenderness of the patella,
inability to flex the knee to 90 degrees, or inability to bear weight for 4 consecutive steps. The
sensitivity of this strategy for picking up fractures was excellent (~100%) and the negative
likelihood ratio was low (0.11) 1, 6.
Conclusions
Given the frequency with which the primary care physician is likely to encounter patients with
knee pain, the studies described above provide at least some guidance for what are most likely to
be the most helpful maneuvers. There is reasonable evidence that negative findings can be relied
upon to rule out significant pathology which might require more expedient referral to a
specialist, which is often a primary concern of the primary care provider at an initial visit. Being
able to use the physical exam to help make these triage decisions will spare the need for at least
some imaging tests, saving time and money. However, the desire to use these techniques in this
manner underscores the importance of adequate training of primary care physicians in the
musculoskeletal exam. Further study of specific maneuvers in the primary care setting will be
necessary to further validate the use of the physical exam to diagnose common knee problems.
References
Jackson J, O’Malley P, Kroenke K, “Evaluation of Acute Knee Pain in Primary Care”, Ann Intern Med
2003; 139(7):575-588.
2. Jinks C, Jordan K, et al, “A brief screening tool for knee pain in primary care (KNEST). Results from a
survey in the general population aged 50 and over”, Rheumatology 2004; 43:55-61.
3. Juhn M, Anderson B, “Patellofemoral pain syndrome”, UpToDate, accessed on 1/28/2005 at
www.uptodateonline.com.
4. Nakamoto G, clinical communication, January 2005.
5. Calmbach W, Hutchens M, “Evaluation of Patients Presenting with Knee Pain: Part I. History, Physical
Examination, Radiographs, and Laboratory Tests”, Am Fam Physician 2003; 68(5).
6. Anderson R, Anderson B, “Evaluation of the patient with knee pain”, UpToDate, accessed 1/ 17/2005 at
www.uptodateonline.com.
7. Solomon D, Simel D, et al, “Does This Patient Have a Torn Meniscus or Ligament of the Knee? Value of
the Physical Examination”, JAMA 2001; 286(13):1610-1620.
8. Allen J, Taylor K, “Physical examination of the knee”, Prim Care Clin Office Pract 2004; 31:887-907.
9. Gardner G, “Evaluation and Treatment of Common Knee Disorders”.
10. Ellis M, Meadows S, “For knee pain, how predictive is physical examination for meniscal injury?”, J Fam
Pract 2004; 53(11).
11. Cibere J, Bellamy N, et al, “Reliability of the Knee Examination in Osteoarthritis: Effect of
Standardization”, Arthritis & Rheumatism 2004; 50(2):458-468.
12. Calmbach W, Hutchens M, “Evaluation of Patients Presenting with Knee Pain: Part II. Differential
Diagnosis”, Am Fam Physician 2003; 68(5).
1.
7