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Evaluation of the knee
The Journal
ofEmergency Medicme,
Vol. 4, pp. 133-143. 1986
EVALUATION
Printed in the USA
Copyright @ 1986 Pergamon Journals Ltd
OF THE KNEE
George L. Sternbach, Department of Emergency
l
MD
Serwces, Stanford University Medical Center, Callfornla 94305
0 Abstract-The knee is frequently injured and affected by a variety of diseases. A precise history of injury or onset of symptoms is essential. The joint is ideally examined as soon after injury as possible. Examination should include observation of swelling, palpation of bony prominences, determination of the presence of effusion, recording of range of motion and evaluation of joint stability. Although x-ray studies constitute an important part of overall assessment, they only augment and not supplant thorough physical examination. Aspiration of joint effusion should be performed for diagnostic purposes, or to relieve pain. Arthrocentesis is indicated when effusion of uncertain etiology is present. 0 Keywords - knee injury; knee examination; arthritis
history. External rotation of the knee, especially when accompanied by the application of a medially directed force to the lateral side, is likely to result in medial collateral ligament injury and may produce injury to the anterior cruciate ligament or medial meniscus. Hyperextension injuries may tear the anterior cruciate ligament. Falls onto the patella may produce patellar fracture or damage to the posterior cruciate ligament. Activities that involve internal rotation of the femur, external rotation of the leg, and flexion of the knee stress the stability of the patella. At least 10% of all athleticrelated knee injuries are associated with subluxation or dislocation of the patella, most occurring in adolescents or young adults.’
History The knee is susceptible to traumatic injury and is frequently affected by a variety of diseases. A complete history from the patient should include that of involvement of other joints, presence of systemic infection or other illness, and the use of medications. Occasionally, a patient’s knee pain is referred from the hip or spine. Although a precise description of the mechanism of injury is extremely useful in localizing the site of trauma, many patients are unable to provide a sufficiently detailed
Physical Examination The joint is ideally examined as soon after injury as possible. Once swelling, hemorrhage, and muscular spasm develop, examination is severely hindered. When this occurs, it may be necessary to institute immobilization and non-weight-bearing for several days until adequate assessment may be conducted. The bony landmarks of the knee are prominent, and the joint is readily amen-
Techniques and Procedures features practical, “how-to” articles of interest to all prac-
ticing emergency physicians. This section is coordinated by George Sternbach, MD, Stanford University Medical Center. RECEIVED:1 May 1984; ACCEPTED: 19 June 1985 0736-4679/86 $3.00 + .OO
-
133
134
able to physical evaluation. Observation should be directed toward identification of bursal or intra-articular swelling. Bursal swelling may be identified in the prepatellar, infrapatellar, and pes anserine bursae, and occasionally in the popliteal fossa. The prepatellar bursa lies anterior to the infrapatellar tendon. It may become inflamed as a result of excessive kneeling, giving rise to the lay term “house-maid’s knee.” The pes anserine bursa is located at the proximal medial aspect of the tibia, just medial to the tibia1 tubercle. Inflammation of the popliteal or gastrocnemiosemimembranosus bursa (Baker’s cyst) is usually related to rheumatoid disease. Rupture of this bursa may result in the escape of bursal fluid into the calf, producing a clinical picture that mimics thrombophlebitis.2
Joint Effusion Frequently accompanying significant injury or disease is joint effusion. Intra-articular effusion results in generalized swelling and slight flexion of the knee. The presence of a large effusion can be confirmed by pushing the patella of the extended knee into the trochlear groove and then releasing it. Movement of intra-articular fluid first to the sides of the joint and then beneath the patella will cause that bone to rebound. This is known as patellar ballottement. This sign will not, however, be produced by a smaller effusion, in which case, the knee should be extended, and fluid from the suprapatellar bursa and lateral side of the joint forced to the medial side by external compression. Gently tapping over the distended medial side will cause fluid to traverse the knee, creating a fullness laterally.3 The range of motion of the knee should be recorded. Normal range of motion extends from 0” in full extension to approximately 135” in flexion. The normal supine patient can flex the knee until the heel nearly touches the buttock. Palpation of the bony prominences should then be carried out. The collateral ligaments
George L. Sternbach
and quadriceps mechanism structures are also readily palpable. A portion of the medial meniscus is palpable over the medial joint line with the leg internally rotated. The lateral meniscus is palpable at the lateral joint line with the knee in slight flexion.
Joint Stabiliry The joint’s stability should then be evaluated. Medial and lateral stability should be assessed both in extension and in 30” of flexion. With the patient supine, lower the leg over the side of the examining table and support it during stress testing. This will ensure maximal muscular relaxation. Apply stress the knee from both the medial (Figure 1) and lateral sides. Comparison should be made to the degree of motion present on the uninvolved side. A classification of the degree of ligamentous disruption is listed in Table 1. Partial ligamentous disruption results in tenderness that is elicited at the joint line and over the ligament itself, most commonly over the femoral origin. The presence of instability in full extension calls for consideration of immediate surgery, as does the presence of instability at 30” when accompanied by anterior instability. Anteroposterior stability is provided by the cruciate ligaments. Their integrity is ascertained by the “drawer” tests. With the patient supine and the knee flexed to 90”, the foot is stablized, and an effort is made to draw the tibia anteriorly and posteriorly (Figure 2). The maneuver should be repeated in nearly full extension, as well as in internal and external rotation. The degree of motion should be compared with the opposite side. Anterior laxity with the leg in neutral position relative to the thigh indicates injury to the anterior cruciate ligament. Laxity elicited in internal rotation implies disruption of the posterior cruciate ligament as well. False negative findings with this maneuver may occur for a number of reasons. The presence of effusion may prevent knee flexion to 90”. Hamstring muscle contrac-
Evaluation
135
of the Knee
likelihood of hamstring muscle spasm masking instability by decreasing the moment arm of these muscles as they act on the knee is reduced.4
Common Knee Syndromes
Figure 1. Testing for medial instability: The examiner’s tight hand is placed such that the thenar eminence rests against the fibular head. The left hand grasps the leg. Force is applied in a medial direction by the right hand in an effort to elicit instability. The position of the hands should be reversed to test for lateral instability.
tion due to pain may mask instability. Laxity may not be elicited if the examiner applies insufficient force while performing the test.4 Some clinicians consider the Lachman test to be more reliable for demonstrating anterior cruciate instability. To perform this test, the knee is flexed 15” to 20”, the femur stabilized with one examining hand grasping the thigh laterally just proximal to the patella and the proximal tibia gripped by the other hand (Figure 3). Anteroposterior motion of the tibia with respect to the stabilized femur is then attempted, similar to the way this is done in the drawer test. The Lachman test possesses several advantages. It does not require as much knee flexion. The blocking effect of the posterior horns of the menisci is minimized, The
When the posterior cruciate ligament is ruptured, the tibia sags posteriorly, so that the normal 5 to 10 cm forward step-off of the tibia1 plateau is lost. The palpating finger runs straight from the femoral condyle onto the anterior tibia1 surface. Injuries to the posterior cruciate ligament are less common, however, constituting only 1% of all knee ligament injuries.4 The anterior cruciate ligament is much more frequently injured. Injury is frequently heralded by an audible “pop” and accompanied by immediate instability and effusion. Although it may be isolated, such injury is frequently accompanied by damage to the medial collateral ligament or medial meniscus. Injury to the menisci is usually due to rotational forces or a direct blow to the flexed knee. Pain is usually immediate, is accompanied by effusion, and is most severe upon weight-bearing. This feature may help distinguish meniscus injury from ligamentous sprain, in which pain occurs both during weight-bearing and non-weight-bearing motion. Locking of the knee is typically due to meniscus injury. Although flexion is free, extension is limited in the locked knee. Tenderness is localized to the medial or lateral joint space. The patient may report that the knee “clicks” or “pops.” Such sounds may be reproduced by performing the McMurray test. With the patient supine and the knee flexed, the leg is internally and then externally rotated. Then the knee is extended while medially-directed stress is applied (Figure 4). A palpable or audible “click” constitutes an indication of a torn medial meniscus. Symptoms suggesting meniscus injury may also be produced by the presence of intra-articular chips of bone or cartilage.
136
George L. Sternbach
Table 1. Severity of Collateral Ligamentous Disruption Grade
Pathology
Physical Findings
Microscopic tearing of the ligamentous complex.
No instability detected.
Gross disruption of ligamentous fibers.
More laxity by 5O-15O than normal side when tested at 30° of flexion. May be stable in full extention. Laxity elicited when joint tested in extension.
Complete loss of anatomical integrity.
Stress X-ray Findings Widening of joint space (“opening”) of up to 5 mm with stress. 5-10 mm of “opening.”
Greater than 10 mm of “opening.”
Figure 2. Testing for anteroposterior instability: With the patient supine and the knee flexed at 90°, the foot is stabilized by having the examiner sit on it. The knee is grasped as Illustrated, with the thumbs along the joint line and the fingers along the area of the medial and lateral hamstring insartions. The tibia is then drawn toward and away from the examiner.
These clips may appear on plain x-ray studies and be the result of injury or osteoarthritis. Patients with osteoarthritis complain of pain with activity, which is relieved by rest. Small joint effusions and quadriceps muscle atrophy are common. Hypertrophic bone may be palpable. There is frequently limitation of motion at the extremes of flexion and extension, and ligamentous instability may be present. Patellar chondromalacia is a degenera-
tive process of the patellar cartilage which may progress to patellar-femoral osteoarthritis. It typically affects younger individuals and produces anterior or retropatellar knee pain that is felt at rest following activity and is especially troub1esom.e during descent of stairs. The patient may complain of “catching, ” “grating,” or transient locking of the knee. Patellar tenderness may be elicited, especially on compression of the patella against the femoral condyles. Patel-
137
Evaluation of the Knee
Figure 3. The Lachman Test: In this illustration the lateral thigh is grasped just proximal to the patella and the proximal leg gripped by the other hand. With the knee flexed 15’ to 20°, the anterior and posterior stress is applied to the tibia In an effort to ascertain the presence of instabllljy.
lar crepitation may also be palpable. A summary of findings in common knee syndromes is found in Table 2. Rheumatoid arthritis may affect the knee, although other joints are usually also involved, generally in a symmetrical distribution. Involvement of non-weight-bearing joints is typical. Swelling involves the soft tissue of the joint rather than the bone itself, as is typical of osteoarthritis. A variable amount of inflammation and muscular atrophy may be present. Tenderness, when present, generally involves the entire joint, rather than being localized. Septic arthritis frequently involves the knee and typically produces the classical findings of inflammation: pain, swelling, heat, and redness of the skin overlying the joint. Although septic arthritis is generally monoarticular, migratory polyarthralgias may precede the localization of infection. Findings of infection may be less dramatic when the process is superimposed on a joint previously involved by another form of arthritis. The diagnosis must be confirmed by
arthrocentesis. Gout frequently involves the knee, and this is also the joint most often affected by pseudogout. Some clinical aspects of the different kinds of arthritis commonly involving the knee are listed in Table 3.
X-ray Studies Although radiographic evaluation of the knee constitutes an important part of overall assessment, it only augments and does not supplant thorough physical evaluation. Because significant soft-tissue injury may exist in the absence of any radiographic abnormality, normal-x-ray studies may be seen despite the presence of substantial pathology. Standard views of the knee include anteroposterior, lateral, and oblique projections. Special views may be necessary. When there is injury to or pain in the patella, an axial or “sunrise” view should be ordered. Stress views taken with the leg adducted
138
George L. Sternbach
Figure 4. The McMurraytest: The knee is flexed and the foot held with the fingers touching the medial joint line and the thumb and thenar emlnbnce along the lateral joint line. The leg is alternately rotated internally and externally. Then with laterally directed force applied to the knee and the leg externallv rotated. the knee is slowlv extended. An audible or palpable click within the joint is suggestive of a-torn mebial meniscus. -
and abducted indicate the degree of stability of the,lateral and medial collateral complexes. If collateral ligament injury is suspected, such views may quantify the degree of injury (see Table 2). Nevertheless, stress views.+ay be inconclusive if pain or muscular spasm. are prominent in the immediate posttraumatic period. The most common chronic affliction of the knee is osteoarthritis. Early radiographic changes that help differentiate this entity from other formsof arthritis may be present (Figure 5). Intra-articular bony chips may be visible. Abnormal x-ray -findings are uncommon in gout or rheumatoid arthritis until these diseases ‘are advanced. Soft-tissue swelling and effusion may be seen early in the course of rheumatoid arthritis. Although
effusion may be detected on an x-ray study, it may just as readily be ascertained on physical examination. Calcification of the articular cartilage (Figure 6) is well-known in pseudogout, but this finding may also be seen in gout, rheumatoid arthritis, and hyperparathyroidism.
Arthrocentesis Joint fluid may be aspirated to aid in the diagnosis or to relieve pain caused by intraarticular fluid accumulation. Arthrocentesis should be carried out in the presence of a joint effusion of uncertain etiology.5 The possible presence of septic arthritis must particularly be diagnosed or excluded by means of synovial fluid analysis. Synovial
May be present
May be present
Usually present
Collateral ligament sprain
Meniscus tear
Cruciate ligament tear
No
Patellar chondromalacia
No
No
May be present
No
Present
No
No
Over medial, lateral, or anterior joint line.
Over ligament
Over patella
Over bursa
Localized Tenderness
Knee Syndromes
Bursitis
of Common Extracapsular Swelling
Features
Effusion
Table 2. Diagnostic
May be diminished by effusion
Diminished
Full or diminished
Full
Full
Range of Motion
Anteroposterior instability present
Medial or lateral instability may be present. No
No
No
Instability
Locking of knee may occur; crepitation may be palpable or audible. McMurray test may be positive. History of audible “pop” or “snap” at time of injury very characteristic.
Signs of inflammation of skin: redness, heat, tenderness. Contraction of quadriceps against patellar pressure may produce pain. Effusion and pain may be greater with partial than with complete tears.
Other Features
2
0
arthritis
Females > males
Sexual Predominance
Joints Involved
Clinical Features of Joint Involvement
Extra-Articular Features
Useful Laboratory Findings
None specific
Rheumatoid factor positive in 75% of patients. Anemia may be present.
None
Systemic involvement is common; subcutanous nodules, muscular atrophy, vasomotor instability, and cutaneous atrophy frequently seen.
None
None
WSC and ESR likely to be elevated; presence of bacteria on Gram’s stain or culture is diagnostic.
Joint pain on motion or at rest; fusiform thickening of periarticular soft tissue in long-standing cases; acutely involved joint may have inflammatory appearance similar to gout or septic arthritis.
Table 3. Clinical Features of Forms of Arthritis Commonly Involving the Knee
Rheumatoid
Osteoarthritis
Pain primarily on motion; deformity due to bony proliferation; crepitation and muscular atrophy common: joint effusion may be present. Swelling, redness, heat, and tenderness
Swelling, heat, redness, and severe tenderness in acutely involved joint.
Frequently monoarticular; usually asymmetric distribution when polyarticular.
Usually
Similar to gout.
monoarticular
Usually monoarticular; occasionally polyarticular.
Findings or history of a febrile illness or a source of infection; migratory polyarthralgias may precede joint localization. Tenosynovitis may be present. Tophi may be present.
Bilateral, symmetrical involvement is the rule, with monoarticular arthritis being less common; the proximal interphalangeal and metacarpophalangeal joints are the ones most commonly involved. Multiple-joint involvement is usual; distal interphalangeal joints of hands most commonly affected.
Septic arthritis
females
None, except in gonococcal arthritis, in which females> males.
7
Males >
None
Gout
Pseudogout
Increased serum uric acid frequently present; finding of urate crystals in joint fluid is diagnostic. Presence of calcium pyrophosphate crystals in joint fluid is diagnostic.
m of the Knee Evaluz 3tic
141
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Figure 5aI. Osteoarthritis: Early x-ray findings include the development of small spulrs ala w the joint margirle. Narrowing’ of the joint space also appears early and may be the first sign of invol venRent. Howevrer, such narrowlng may not be obvious if non-weight-bearing films are talten.
fluid findings may be pathognomic in the cases of gout, pseudogout, septic arthritis, hemarthrosis, and lipohemarthrosis. In addition, inflammatory processes can be differentiated from noninflammatory ones by means of synovial fluid analysis. The knee is the most easily aspirated joint in the body. Strict aspetic technique should always be employed. Arthrocentesis is contraindicated in the presence of infected skin or subcutaneous tissue overlying the joint. The needle should be introduced on the medial surface of the fully extended knee and advanced between the inferior surface of the patella and the patellar groove of the femur. The quadriceps muscle must
be completely relaxed for the needle to be advanced readily. Contraction of the quadriceps will clamp the patella firmly in its groove and impede insertion of the needle. It is rarely necessary to advance the needle to the hub, the joint space frequently being encountered about a half inch from skin level. In the presence of a large quantity of intra-articular fluid, the knee may alternatively be aspirated by entering the suprapatellar bursa at a point just lateral and superior to the patella. The presence of fat globules in a hemorrhagic aspirate is indicative of a fracture, even if this cannot be identified on an x-ray study. When hemarthrosis develops imme-
George L. Sternbach
Figure 5b. Weight-bearing films of the same patient, showing marked joint space is almost always asymmetric, with involvement of the medial side usually being more severe. Increased density of the bony articular surfaces may also be seen.
Figure 6. Chondrocalcinosis:Calcium deposition in the articular cartilage is seen in the knee as a somewhat granular line of increased density parallelling the bony articular surfaces.
diately or within several hours of injury, damage to an important articular structure is likely. Injuries commonly accompanied by immediate swelling include osteochondral fractures, anterior cruciate ligament and meniscus tears, and second- or thirddegree collateral ligament sprains. Swelling that develops more than four hours following injury is likely to be due to synovial irritation, first-degree ligamentous sprains, or meniscus tears. The early development of hemarthrosis
following injury frequently speaks for the presence of significant bony or soft-tissue damage, even in the absence of demonstrable joint laxity or instability.’ Early orthopedic consultation is warranted in these cases. Such consultation should also be obtained in cases of lipohemarthrosis and septic arthritis. The presence of collateral ligament instability in full extension calls for consideration of immediate surgery, as does the presence of instability at 30” when accompanied by anterior instability.
143
Evaluation of the Knee
REFERENCES 1. Zimbler S, Smith J, Scheller A, et al: Recurrent subluxation and dislocation of the patella in association with athletic injuries. Orthop Clin Norfh Am
4. Howe J, Johnson Sports
Med
RJ: Knee injuries in skiing.
C/in
1982; 1~277-294.
BNW, Sosman JL: The radiology of arthritis. Orthop Clin North Am 1975;
Clin North Am 1979; 10:21-36. 6. Sternbach CL, Baker FJ II: The emergency joint: arthrocentesis and synovial fluid analysis. .I Am
S: Physical examination of the knee joint by complaint. Orthop Clin North Am 1979;
Colt Emerg Physicians 1976; 5~787-792. 7. DeHaven KE: Diagnosis of acute knee injuries with hemarthrosis. Am J Sports Med 1980; 8:9-14.
1980;
11:755-770.
2. Weissman
rheumatoid 6:653-674. 3. Hoppenfeld 10:3-20.
5. Blau SP: The synovial fluid. Orthop
ofEmergency Medicme,
Vol. 4, pp. 133-143. 1986
EVALUATION
Printed in the USA
Copyright @ 1986 Pergamon Journals Ltd
OF THE KNEE
George L. Sternbach, Department of Emergency
l
MD
Serwces, Stanford University Medical Center, Callfornla 94305
0 Abstract-The knee is frequently injured and affected by a variety of diseases. A precise history of injury or onset of symptoms is essential. The joint is ideally examined as soon after injury as possible. Examination should include observation of swelling, palpation of bony prominences, determination of the presence of effusion, recording of range of motion and evaluation of joint stability. Although x-ray studies constitute an important part of overall assessment, they only augment and not supplant thorough physical examination. Aspiration of joint effusion should be performed for diagnostic purposes, or to relieve pain. Arthrocentesis is indicated when effusion of uncertain etiology is present. 0 Keywords - knee injury; knee examination; arthritis
history. External rotation of the knee, especially when accompanied by the application of a medially directed force to the lateral side, is likely to result in medial collateral ligament injury and may produce injury to the anterior cruciate ligament or medial meniscus. Hyperextension injuries may tear the anterior cruciate ligament. Falls onto the patella may produce patellar fracture or damage to the posterior cruciate ligament. Activities that involve internal rotation of the femur, external rotation of the leg, and flexion of the knee stress the stability of the patella. At least 10% of all athleticrelated knee injuries are associated with subluxation or dislocation of the patella, most occurring in adolescents or young adults.’
History The knee is susceptible to traumatic injury and is frequently affected by a variety of diseases. A complete history from the patient should include that of involvement of other joints, presence of systemic infection or other illness, and the use of medications. Occasionally, a patient’s knee pain is referred from the hip or spine. Although a precise description of the mechanism of injury is extremely useful in localizing the site of trauma, many patients are unable to provide a sufficiently detailed
Physical Examination The joint is ideally examined as soon after injury as possible. Once swelling, hemorrhage, and muscular spasm develop, examination is severely hindered. When this occurs, it may be necessary to institute immobilization and non-weight-bearing for several days until adequate assessment may be conducted. The bony landmarks of the knee are prominent, and the joint is readily amen-
Techniques and Procedures features practical, “how-to” articles of interest to all prac-
ticing emergency physicians. This section is coordinated by George Sternbach, MD, Stanford University Medical Center. RECEIVED:1 May 1984; ACCEPTED: 19 June 1985 0736-4679/86 $3.00 + .OO
-
133
134
able to physical evaluation. Observation should be directed toward identification of bursal or intra-articular swelling. Bursal swelling may be identified in the prepatellar, infrapatellar, and pes anserine bursae, and occasionally in the popliteal fossa. The prepatellar bursa lies anterior to the infrapatellar tendon. It may become inflamed as a result of excessive kneeling, giving rise to the lay term “house-maid’s knee.” The pes anserine bursa is located at the proximal medial aspect of the tibia, just medial to the tibia1 tubercle. Inflammation of the popliteal or gastrocnemiosemimembranosus bursa (Baker’s cyst) is usually related to rheumatoid disease. Rupture of this bursa may result in the escape of bursal fluid into the calf, producing a clinical picture that mimics thrombophlebitis.2
Joint Effusion Frequently accompanying significant injury or disease is joint effusion. Intra-articular effusion results in generalized swelling and slight flexion of the knee. The presence of a large effusion can be confirmed by pushing the patella of the extended knee into the trochlear groove and then releasing it. Movement of intra-articular fluid first to the sides of the joint and then beneath the patella will cause that bone to rebound. This is known as patellar ballottement. This sign will not, however, be produced by a smaller effusion, in which case, the knee should be extended, and fluid from the suprapatellar bursa and lateral side of the joint forced to the medial side by external compression. Gently tapping over the distended medial side will cause fluid to traverse the knee, creating a fullness laterally.3 The range of motion of the knee should be recorded. Normal range of motion extends from 0” in full extension to approximately 135” in flexion. The normal supine patient can flex the knee until the heel nearly touches the buttock. Palpation of the bony prominences should then be carried out. The collateral ligaments
George L. Sternbach
and quadriceps mechanism structures are also readily palpable. A portion of the medial meniscus is palpable over the medial joint line with the leg internally rotated. The lateral meniscus is palpable at the lateral joint line with the knee in slight flexion.
Joint Stabiliry The joint’s stability should then be evaluated. Medial and lateral stability should be assessed both in extension and in 30” of flexion. With the patient supine, lower the leg over the side of the examining table and support it during stress testing. This will ensure maximal muscular relaxation. Apply stress the knee from both the medial (Figure 1) and lateral sides. Comparison should be made to the degree of motion present on the uninvolved side. A classification of the degree of ligamentous disruption is listed in Table 1. Partial ligamentous disruption results in tenderness that is elicited at the joint line and over the ligament itself, most commonly over the femoral origin. The presence of instability in full extension calls for consideration of immediate surgery, as does the presence of instability at 30” when accompanied by anterior instability. Anteroposterior stability is provided by the cruciate ligaments. Their integrity is ascertained by the “drawer” tests. With the patient supine and the knee flexed to 90”, the foot is stablized, and an effort is made to draw the tibia anteriorly and posteriorly (Figure 2). The maneuver should be repeated in nearly full extension, as well as in internal and external rotation. The degree of motion should be compared with the opposite side. Anterior laxity with the leg in neutral position relative to the thigh indicates injury to the anterior cruciate ligament. Laxity elicited in internal rotation implies disruption of the posterior cruciate ligament as well. False negative findings with this maneuver may occur for a number of reasons. The presence of effusion may prevent knee flexion to 90”. Hamstring muscle contrac-
Evaluation
135
of the Knee
likelihood of hamstring muscle spasm masking instability by decreasing the moment arm of these muscles as they act on the knee is reduced.4
Common Knee Syndromes
Figure 1. Testing for medial instability: The examiner’s tight hand is placed such that the thenar eminence rests against the fibular head. The left hand grasps the leg. Force is applied in a medial direction by the right hand in an effort to elicit instability. The position of the hands should be reversed to test for lateral instability.
tion due to pain may mask instability. Laxity may not be elicited if the examiner applies insufficient force while performing the test.4 Some clinicians consider the Lachman test to be more reliable for demonstrating anterior cruciate instability. To perform this test, the knee is flexed 15” to 20”, the femur stabilized with one examining hand grasping the thigh laterally just proximal to the patella and the proximal tibia gripped by the other hand (Figure 3). Anteroposterior motion of the tibia with respect to the stabilized femur is then attempted, similar to the way this is done in the drawer test. The Lachman test possesses several advantages. It does not require as much knee flexion. The blocking effect of the posterior horns of the menisci is minimized, The
When the posterior cruciate ligament is ruptured, the tibia sags posteriorly, so that the normal 5 to 10 cm forward step-off of the tibia1 plateau is lost. The palpating finger runs straight from the femoral condyle onto the anterior tibia1 surface. Injuries to the posterior cruciate ligament are less common, however, constituting only 1% of all knee ligament injuries.4 The anterior cruciate ligament is much more frequently injured. Injury is frequently heralded by an audible “pop” and accompanied by immediate instability and effusion. Although it may be isolated, such injury is frequently accompanied by damage to the medial collateral ligament or medial meniscus. Injury to the menisci is usually due to rotational forces or a direct blow to the flexed knee. Pain is usually immediate, is accompanied by effusion, and is most severe upon weight-bearing. This feature may help distinguish meniscus injury from ligamentous sprain, in which pain occurs both during weight-bearing and non-weight-bearing motion. Locking of the knee is typically due to meniscus injury. Although flexion is free, extension is limited in the locked knee. Tenderness is localized to the medial or lateral joint space. The patient may report that the knee “clicks” or “pops.” Such sounds may be reproduced by performing the McMurray test. With the patient supine and the knee flexed, the leg is internally and then externally rotated. Then the knee is extended while medially-directed stress is applied (Figure 4). A palpable or audible “click” constitutes an indication of a torn medial meniscus. Symptoms suggesting meniscus injury may also be produced by the presence of intra-articular chips of bone or cartilage.
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George L. Sternbach
Table 1. Severity of Collateral Ligamentous Disruption Grade
Pathology
Physical Findings
Microscopic tearing of the ligamentous complex.
No instability detected.
Gross disruption of ligamentous fibers.
More laxity by 5O-15O than normal side when tested at 30° of flexion. May be stable in full extention. Laxity elicited when joint tested in extension.
Complete loss of anatomical integrity.
Stress X-ray Findings Widening of joint space (“opening”) of up to 5 mm with stress. 5-10 mm of “opening.”
Greater than 10 mm of “opening.”
Figure 2. Testing for anteroposterior instability: With the patient supine and the knee flexed at 90°, the foot is stabilized by having the examiner sit on it. The knee is grasped as Illustrated, with the thumbs along the joint line and the fingers along the area of the medial and lateral hamstring insartions. The tibia is then drawn toward and away from the examiner.
These clips may appear on plain x-ray studies and be the result of injury or osteoarthritis. Patients with osteoarthritis complain of pain with activity, which is relieved by rest. Small joint effusions and quadriceps muscle atrophy are common. Hypertrophic bone may be palpable. There is frequently limitation of motion at the extremes of flexion and extension, and ligamentous instability may be present. Patellar chondromalacia is a degenera-
tive process of the patellar cartilage which may progress to patellar-femoral osteoarthritis. It typically affects younger individuals and produces anterior or retropatellar knee pain that is felt at rest following activity and is especially troub1esom.e during descent of stairs. The patient may complain of “catching, ” “grating,” or transient locking of the knee. Patellar tenderness may be elicited, especially on compression of the patella against the femoral condyles. Patel-
137
Evaluation of the Knee
Figure 3. The Lachman Test: In this illustration the lateral thigh is grasped just proximal to the patella and the proximal leg gripped by the other hand. With the knee flexed 15’ to 20°, the anterior and posterior stress is applied to the tibia In an effort to ascertain the presence of instabllljy.
lar crepitation may also be palpable. A summary of findings in common knee syndromes is found in Table 2. Rheumatoid arthritis may affect the knee, although other joints are usually also involved, generally in a symmetrical distribution. Involvement of non-weight-bearing joints is typical. Swelling involves the soft tissue of the joint rather than the bone itself, as is typical of osteoarthritis. A variable amount of inflammation and muscular atrophy may be present. Tenderness, when present, generally involves the entire joint, rather than being localized. Septic arthritis frequently involves the knee and typically produces the classical findings of inflammation: pain, swelling, heat, and redness of the skin overlying the joint. Although septic arthritis is generally monoarticular, migratory polyarthralgias may precede the localization of infection. Findings of infection may be less dramatic when the process is superimposed on a joint previously involved by another form of arthritis. The diagnosis must be confirmed by
arthrocentesis. Gout frequently involves the knee, and this is also the joint most often affected by pseudogout. Some clinical aspects of the different kinds of arthritis commonly involving the knee are listed in Table 3.
X-ray Studies Although radiographic evaluation of the knee constitutes an important part of overall assessment, it only augments and does not supplant thorough physical evaluation. Because significant soft-tissue injury may exist in the absence of any radiographic abnormality, normal-x-ray studies may be seen despite the presence of substantial pathology. Standard views of the knee include anteroposterior, lateral, and oblique projections. Special views may be necessary. When there is injury to or pain in the patella, an axial or “sunrise” view should be ordered. Stress views taken with the leg adducted
138
George L. Sternbach
Figure 4. The McMurraytest: The knee is flexed and the foot held with the fingers touching the medial joint line and the thumb and thenar emlnbnce along the lateral joint line. The leg is alternately rotated internally and externally. Then with laterally directed force applied to the knee and the leg externallv rotated. the knee is slowlv extended. An audible or palpable click within the joint is suggestive of a-torn mebial meniscus. -
and abducted indicate the degree of stability of the,lateral and medial collateral complexes. If collateral ligament injury is suspected, such views may quantify the degree of injury (see Table 2). Nevertheless, stress views.+ay be inconclusive if pain or muscular spasm. are prominent in the immediate posttraumatic period. The most common chronic affliction of the knee is osteoarthritis. Early radiographic changes that help differentiate this entity from other formsof arthritis may be present (Figure 5). Intra-articular bony chips may be visible. Abnormal x-ray -findings are uncommon in gout or rheumatoid arthritis until these diseases ‘are advanced. Soft-tissue swelling and effusion may be seen early in the course of rheumatoid arthritis. Although
effusion may be detected on an x-ray study, it may just as readily be ascertained on physical examination. Calcification of the articular cartilage (Figure 6) is well-known in pseudogout, but this finding may also be seen in gout, rheumatoid arthritis, and hyperparathyroidism.
Arthrocentesis Joint fluid may be aspirated to aid in the diagnosis or to relieve pain caused by intraarticular fluid accumulation. Arthrocentesis should be carried out in the presence of a joint effusion of uncertain etiology.5 The possible presence of septic arthritis must particularly be diagnosed or excluded by means of synovial fluid analysis. Synovial
May be present
May be present
Usually present
Collateral ligament sprain
Meniscus tear
Cruciate ligament tear
No
Patellar chondromalacia
No
No
May be present
No
Present
No
No
Over medial, lateral, or anterior joint line.
Over ligament
Over patella
Over bursa
Localized Tenderness
Knee Syndromes
Bursitis
of Common Extracapsular Swelling
Features
Effusion
Table 2. Diagnostic
May be diminished by effusion
Diminished
Full or diminished
Full
Full
Range of Motion
Anteroposterior instability present
Medial or lateral instability may be present. No
No
No
Instability
Locking of knee may occur; crepitation may be palpable or audible. McMurray test may be positive. History of audible “pop” or “snap” at time of injury very characteristic.
Signs of inflammation of skin: redness, heat, tenderness. Contraction of quadriceps against patellar pressure may produce pain. Effusion and pain may be greater with partial than with complete tears.
Other Features
2
0
arthritis
Females > males
Sexual Predominance
Joints Involved
Clinical Features of Joint Involvement
Extra-Articular Features
Useful Laboratory Findings
None specific
Rheumatoid factor positive in 75% of patients. Anemia may be present.
None
Systemic involvement is common; subcutanous nodules, muscular atrophy, vasomotor instability, and cutaneous atrophy frequently seen.
None
None
WSC and ESR likely to be elevated; presence of bacteria on Gram’s stain or culture is diagnostic.
Joint pain on motion or at rest; fusiform thickening of periarticular soft tissue in long-standing cases; acutely involved joint may have inflammatory appearance similar to gout or septic arthritis.
Table 3. Clinical Features of Forms of Arthritis Commonly Involving the Knee
Rheumatoid
Osteoarthritis
Pain primarily on motion; deformity due to bony proliferation; crepitation and muscular atrophy common: joint effusion may be present. Swelling, redness, heat, and tenderness
Swelling, heat, redness, and severe tenderness in acutely involved joint.
Frequently monoarticular; usually asymmetric distribution when polyarticular.
Usually
Similar to gout.
monoarticular
Usually monoarticular; occasionally polyarticular.
Findings or history of a febrile illness or a source of infection; migratory polyarthralgias may precede joint localization. Tenosynovitis may be present. Tophi may be present.
Bilateral, symmetrical involvement is the rule, with monoarticular arthritis being less common; the proximal interphalangeal and metacarpophalangeal joints are the ones most commonly involved. Multiple-joint involvement is usual; distal interphalangeal joints of hands most commonly affected.
Septic arthritis
females
None, except in gonococcal arthritis, in which females> males.
7
Males >
None
Gout
Pseudogout
Increased serum uric acid frequently present; finding of urate crystals in joint fluid is diagnostic. Presence of calcium pyrophosphate crystals in joint fluid is diagnostic.
m of the Knee Evaluz 3tic
141
-
Figure 5aI. Osteoarthritis: Early x-ray findings include the development of small spulrs ala w the joint margirle. Narrowing’ of the joint space also appears early and may be the first sign of invol venRent. Howevrer, such narrowlng may not be obvious if non-weight-bearing films are talten.
fluid findings may be pathognomic in the cases of gout, pseudogout, septic arthritis, hemarthrosis, and lipohemarthrosis. In addition, inflammatory processes can be differentiated from noninflammatory ones by means of synovial fluid analysis. The knee is the most easily aspirated joint in the body. Strict aspetic technique should always be employed. Arthrocentesis is contraindicated in the presence of infected skin or subcutaneous tissue overlying the joint. The needle should be introduced on the medial surface of the fully extended knee and advanced between the inferior surface of the patella and the patellar groove of the femur. The quadriceps muscle must
be completely relaxed for the needle to be advanced readily. Contraction of the quadriceps will clamp the patella firmly in its groove and impede insertion of the needle. It is rarely necessary to advance the needle to the hub, the joint space frequently being encountered about a half inch from skin level. In the presence of a large quantity of intra-articular fluid, the knee may alternatively be aspirated by entering the suprapatellar bursa at a point just lateral and superior to the patella. The presence of fat globules in a hemorrhagic aspirate is indicative of a fracture, even if this cannot be identified on an x-ray study. When hemarthrosis develops imme-
George L. Sternbach
Figure 5b. Weight-bearing films of the same patient, showing marked joint space is almost always asymmetric, with involvement of the medial side usually being more severe. Increased density of the bony articular surfaces may also be seen.
Figure 6. Chondrocalcinosis:Calcium deposition in the articular cartilage is seen in the knee as a somewhat granular line of increased density parallelling the bony articular surfaces.
diately or within several hours of injury, damage to an important articular structure is likely. Injuries commonly accompanied by immediate swelling include osteochondral fractures, anterior cruciate ligament and meniscus tears, and second- or thirddegree collateral ligament sprains. Swelling that develops more than four hours following injury is likely to be due to synovial irritation, first-degree ligamentous sprains, or meniscus tears. The early development of hemarthrosis
following injury frequently speaks for the presence of significant bony or soft-tissue damage, even in the absence of demonstrable joint laxity or instability.’ Early orthopedic consultation is warranted in these cases. Such consultation should also be obtained in cases of lipohemarthrosis and septic arthritis. The presence of collateral ligament instability in full extension calls for consideration of immediate surgery, as does the presence of instability at 30” when accompanied by anterior instability.
143
Evaluation of the Knee
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