Anatomy of the Knee
See Fig. 55.1 .
Observation and Measurement
Alignment of lower extremities: View the patient from the front, side, and back.
Angular and rotational deformities: Excessive valgus, varus, recurvatum, flexion contracture, and femoral or tibial torsion
Foot alignment and mechanics: Excessive cavus or pes planus; heels should invert and arches increase on toe rising
Leg length inequality: Best judged by pelvic levelness on standing
Difference in size of legs: Atrophy of one limb versus hypertrophy of opposite limb
Popliteal masses: May be seen better in the prone position
Patellar position: With patient’s knees flexed 90 degrees, check from the side to judge a high or low position. The anterior patellar surface normally faces the wall in front of the patient sitting with legs over the side of the examination table. View from the front to judge lateral posture. The patella should appear centered in the soft tissue outline of the knee.
Osgood–Schlatter changes: Enlarged and/or tender tibial tuberosity
Vastus medialis obliquus/vastus lateralis (VMO/VL) relationship: With the patient’s knees held actively at 45 degrees of flexion ( Fig. 55.2 ), the distal one-third of the vastus medialis should normally present as a substantial muscle from the adductor tubercle, inserting into upper the one-third to one-half of the medial patella. Dysplastic vastus medialis obliquus (VMO) appears hollow in this normal muscular location (see Fig. 55.2 ); also observe for apparent hypertrophy of vastus lateralis (VL).
Patellar tracking: Observe on active flexion and extension; watch for excessive displacement of the patella.
Range of motion: Both active and passive; compare the injured with the uninjured side
Muscle bulk: Thigh and calf; can measure circumferences
Quadriceps (Q) angle: With quadriceps contracted, measure the angle between the line from the anterior superior iliac spine to the midpoint of the patella and the line from the midpoint of the patella to the tibial tuberosity (see Fig. 55.2 ); normal in males is ≤10 degrees and in females is ≤15 degrees.
Hamstring and heel cord tightness: See Chapter 42 , Musculoskeletal Injuries in Sports
Range of motion: Lack of full knee flexion may show quadriceps tightness
Popliteal masses: Compare contours with those of the opposite knee
Mechanics of gait: Stance and swing phase from side to side is even; look for limp, other asymmetry, excessive limb rotation, or limb malalignment.
Patellofemoral tracking: Observe the patella closely from the front view.
Joint effusion: With the patient’s knee extended, milk fluid from the suprapatellar pouch, and palpate along medial and lateral sides of the patella (see Fig. 55.2 ). Try to distinguish intra-articular effusion that can be moved about from extra-articular swelling that feels more like thick soft tissue, which is not movable.
Significant areas of tenderness:
Menisci: medial and lateral joint lines
Ligament attachments: medial femoral epicondyle, adductor tubercle, lateral femoral epicondyle, proximal medial tibia
Tendons: patellar tendon, quadriceps tendon, popliteus tendon, hamstrings
Bursae: prepatellar, pes anserinus, tibial collateral ligament, deep infrapatellar
Other: patellar facets, extensor retinaculum
Crepitation: During range of motion —from any rough joint surface (particularly patellofemoral joint), fractures, or soft tissue thickness; patellofemoral compression —longitudinal and/or transverse compression of the patella against the femur. Examine for crepitation or ask regarding any elicited pain.
Muscle tone: Overall turgor of muscle tissue; may be decreased early after injury, even if the bulk still measures normal
Perform all tests on an uninjured knee first to establish “normal” baseline for that patient ( Table 55.1 ).
|Valgus stress test at 30 degrees and 0 degrees||30 degrees: Medial collateral ligament |
0 degrees: Posteromedial corner, medial collateral ligament, posterior cruciate ligament, possibly anterior cruciate ligament
|Varus stress test at 30 degrees and 0 degrees||30 degrees: Lateral collateral ligament |
0 degrees: Posterolateral corner, lateral collateral ligament, posterior cruciate ligament
|Lachman test||Anterior cruciate ligament|
|Anterior drawer test||Anterior cruciate ligament, but affected by other structures such as collaterals|
|Pivot shift test/jerk test||Anterior cruciate ligament|
|Posterior drawer test||Posterior cruciate ligament|
|Gravity or sag test||Posterior cruciate ligament|
|Posterolateral drawer test||Posterolateral corner structures|
|External rotation recurvatum test||Posterolateral corner structures|
|Apley’s compression test||Menisci|
|Apprehension test||Medial patellofemoral ligament and retinaculum|
|Prone external rotation test (dial test)||Posterolateral corner structures|
Valgus stress test at 30 and 0 degrees: The patient is supine and relaxed, with the thigh supported on the table. The examiner applies valgus force at the foot while using other hand as a fulcrum along the lateral side of the joint. Watch and feel for medial joint line opening. Perform first with the knee flexed to 30 degrees, then with maximum possible extension or hyperextension ( Fig. 55.3 ).
Anterior drawer test with external rotation of tibia: The patient is supine and relaxed, with the hip flexed to 45 degrees and knee to 90 degrees. Externally rotate the foot 30 degrees; then, pin the foot to the table with the examiner’s thigh. Grasp the proximal tibia with both hands and pull toward the examiner. A positive test is excessive anterior rotation of the medial tibial condyle (see Fig. 55.3 ).
Varus stress test at 30 and 0 degrees: The patient is in the same position as for the abduction stress test. Reverse the hand position so that one hand applies varus stress while the other acts as a fulcrum along the medial side of the joint. Watch and feel for lateral joint line opening. Perform the test at 30 degrees of flexion and then at full possible extension or hyperextension (see Fig. 55.3 ).
External rotation recurvatum test: The patient is supine and relaxed. Lift the entire lower extremity by the first toe. Observe for excessive recurvatum and external rotation of the proximal tibia (tibial tuberosity) and apparent varus deformity of the knee; indicates posterolateral corner injury
Posterolateral drawer test: Same position as for the anterior drawer test with external rotation of the tibia; the examiner’s hands pushes posteriorly on the proximal tibia; a positive test is excessive posterior rotation of the lateral tibial condyle (see Fig. 55.3 ).
Prone external rotation test (Dial test): The patient is prone with the knees together, and the feet are externally rotated at 30 degrees of knee flexion and then at 90 degrees. The external rotation of the foot relative to the thigh is compared with the contralateral side. The test is positive if there is >10 degrees of rotation of the affected side compared with that of the normal side. If asymmetry is present only at 30 degrees, then isolated posterolateral corner injury is likely. If asymmetry is present at both 30 and 90 degrees, combined injury to the posterior cruciate ligament (PCL) and posterolateral corner is present (see Fig. 55.3 ).
Reverse pivot shift test: Performed with the tibia in external rotation rather than internal rotation; with knee flexed 90 degrees, the lateral tibial condyle is subluxed posteriorly. With further knee extension, tibia reduces with detectable “clunk” (see later discussion of pivot shift test).
Anterior Cruciate Ligament (ACL)
Lachman test: The patient is supine and relaxed; the examiner grasps the distal femur with one hand, while other hand grasps the proximal tibia; knee flexed to approximately 15–20 degrees; apply anterior force to proximal tibia. Positive test is excessive anterior translation of the tibia beneath the femur and lack of a firm endpoint (see Fig. 55.3 ).
Anterior drawer test in neutral rotation: Same position as for anterior drawer with external rotation of the tibia except that foot and tibia are in neutral rotation; anterior pull is applied to the proximal tibia. Positive test is anterior translation of both tibial condyles from beneath the femur (see Fig. 55.3 ). Note: This test is influenced by structures other than anterior cruciate ligament (ACL). Do not rely on this test for diagnosis of ACL tear.
Pivot shift test and jerk test: The patient is supine and relaxed. Begin with knee fully extended (pivot shift test) or flexed to 90 degrees (jerk test); foot and tibia internally rotated; valgus applied at knee; knee progressively flexed (pivot shift test) or extended (jerk test). At approximately 30 degrees, watch and feel for anterior subluxation of lateral tibial condyle: tibia suddenly reduces with further flexion (pivot shift test) or extension (jerk test) (see Fig. 55.3 ).
Posterior Cruciate Ligament (PCL)
Posterior drawer test: Same position as for anterior drawer test in neutral rotation; posterior force is applied to proximal tibia. Positive test is straight posterior displacement of both tibial condyles (see Fig. 55.3 ). Caution: Ensure a neutral position as the starting point. Compare position of the tibia relative to the femur with normal knee. It is easy to start from a posteriorly displaced position and interpret reduction to neutral as a positive anterior drawer sign rather than starting at neutral and interpreting as a positive posterior drawer sign.
Gravity or sag test: The patient is supine and relaxed. Flex hips to 45 degrees and knees to 90 degrees with feet flat on table. With quadriceps relaxed, observe from the lateral side for posterior displacement of one tibial tuberosity compared to the other; then flex the hips to 90 degrees, support both legs by the ankles and feet, and observe again (see Fig. 55.3 ).
Valgus or varus stress test at 0 degrees: As described for abduction and adduction stress tests at 30 and 0 degrees; positive test in full extension in acute case is often due to PCL rupture in addition to injury to associated collateral ligaments (see Fig. 55.3 ).
Joint line tenderness: Tenderness along the medial or lateral joint lines is among the most sensitive findings for a meniscal tear (see Fig. 55.3 ).
McMurray’s test: The patient is supine and relaxed. Have patient flex knee maximally with external tibial rotation (medial meniscus) or internal tibial rotation (lateral meniscus). While maintaining rotation, patient brings the knee into full extension. Positive test is a painful pop occurring over the medial (medial meniscus) or lateral (lateral meniscus) joint line (see Fig. 55.3 ).
Apley’s compression test: The patient is in joint line prone position. Knee is flexed to 90 degrees with external tibial rotation (medial meniscus) or internal tibial rotation (lateral meniscus). Apply axial compression to joint line tibia while joint line patient flexes and extends joint line knee. Positive test is a painful pop over joint line medial (medial meniscus) or lateral (lateral meniscus) joint line (see Fig. 55.3 ).
Hypermobility/apprehension test: The patient is supine and relaxed. The examiner sits on edge of the table with the patient’s knee flexed approximately 30–45 degrees across the examiner’s thigh. With the patient’s quadriceps relaxed, the examiner uses both thumbs to forcefully displace the patella over the lateral femoral condyle. Positive test is increased lateral mobility of the patella compared to the opposite knee or other patients; more important is discomfort or extreme apprehension that the patella is going to dislocate because of lateral displacement.
Plica tests: The patient is supine and relaxed. With the tibia internally rotated, the examiner passively flexes and extends knee from 30 to 100 degrees of flexion. Examining the fingers placed along the medial patellofemoral joint may feel a click, possibly some tenderness, or even a pop of a pathologic plica.
Knee Ligament Injuries
Description: Injury to medial (tibial) collateral ligament and/or medial capsular ligament ( Fig. 55.4 )
Mechanism of injury: Valgus force applied to the knee with external tibial rotation; may be noncontact twist or a blow to lateral side of joint
Presentation: Initial pain on medial side of the knee; with complete tear, complaints of the knee giving way into valgus
Examination: Positive valgus stress test at a 30-degree flexion; compare with opposite knee. An injured medial collateral ligament (MCL) along with disrupted ACL or PCL will result in more gap occurring with a valgus stress test, particularly noticeable when the knee is tested in extension. Frequently, but not always, positive anterior drawer sign results with the tibia in external rotation. The medial tibial condyle rotates anteriorly.
Imaging: Abduction stress radiographs may be used to distinguish ligament injury from epiphyseal fracture in skeletally immature athletes. Fracture opens at the growth plate; ligament tear opens at the joint line; perform in 20–30 degrees of flexion
Differential diagnosis: In young patients, epiphyseal fracture of the distal femur or proximal tibia; patellar dislocation (may be associated with MCL tear); medial meniscus tear (may be associated with MCL tear)
Grades I and II sprains: Rest, ice, compression, and elevation (RICE), crutches, rehabilitation
Grade III sprain (complete ligament tear): With other associated injuries, surgery may be considered (currently rare); if no surgery indicated, immobilization should be used for short period after acute injury; begin rehabilitation program as soon as possible; with only mild instability, rigid immobilization may not be necessary. RICE and functional rehabilitation may be adequate treatment.
Description: Sprain or tear of lateral (fibular) collateral ligament and/or lateral capsular ligament; may be associated injuries to popliteus tendon, iliotibial band, popliteofemoral ligament, and peroneal nerve
Mechanism of injury: Varus or twisting injury; may be contact or noncontact. Posterolateral ligaments often injured by a hyperextension mechanism, frequently with a blow to the anteromedial tibia
Presentation: Pain is present over the lateral ligament complex. Knee may give way on twisting, cutting, or pivoting. In chronic cases, posterolateral corner injury gives a feeling of giving way into hyperextension when standing, walking, or running backward.
Examination: Compare with opposite knee; in acute case, may be increased varus stress test at 30 degrees of flexion and positive posterolateral drawer sign; chronic cases show a positive reverse pivot shift test and external rotation recurvatum test. External rotation recurvatum may also be apparent on standing, giving increased varus appearance to the knee.
Imaging: Lateral capsular sign shows avulsion of the midportion of the lateral capsular ligament with a small fragment of proximal lateral tibia. Associated with a high incidence of anterior cruciate tear and indicates anterolateral instability (see Fig. 55.4 ). Arcuate sign shows avulsion of proximal fibula with the posterolateral ligament complex; indicates posterolateral instability
Differential diagnosis: Chronic posterolateral injury may be confused with medial compartment arthritis because of progressive varus appearance; difficult to differentiate from posterior cruciate injury. Acute lateral ligament injury may be confused with lateral meniscus tear. Injury to the middle third of the lateral capsular ligament, as shown by lateral capsular sign on radiograph, usually associated with ACL injury.
Grade I and II sprains: RICE, crutches, rehabilitation
Grade III sprain (complete ligament tear): Surgical repair is usually preferable if injury involves more than just lateral (fibular) collateral ligament. Immobilization is not really useful by itself. Mild instability may be treated by RICE and functional rehabilitation.
Anterior Cruciate Ligament (ACL)
Description: Tear of part or all of two major bundles (posterolateral and anteromedial) of ACL; may be associated with tears of middle one-third of lateral capsular ligament. ACL is torn from femur or tibia, or torn in its midportion; may avulse tibial spine in young patients (see Fig. 55.4 )
Mechanism of injury: Hyperextension, varus/internal rotation, and extremes of valgus and external rotation are possible causes.
Presentation: Usually a loud pop occurs; may be followed by autonomic symptoms of dizziness, sweating, faintness, and slight nausea. A large swelling usually occurs within first 2 hours after an acute injury (hemarthrosis). Conversely, most acute hemarthroses (85%) are anterior cruciate tears; in chronic cases, complaints of giving way on twisting, pivoting, and cutting
Examination: Acute, large hemarthrosis, positive Lachman test; chronic, positive Lachman test, positive pivot shift test or jerk test; perhaps a positive anterior drawer sign but not reliable; do not rely on the anterior drawer sign
Imaging: Lateral capsular sign; avulsion of the tibial spine may be seen in young patients; magnetic resonance imaging (MRI) useful in acute injury to confirm diagnosis and evaluate for injuries to other structures; reported accuracy rates as high as 95% in detecting ACL tears (see Fig. 55.4 )
Differential diagnosis: Acute, differentiate from other causes of hemarthrosis (e.g., osteochondral fracture, peripheral meniscus tear, and patellar dislocation); chronic, differentiate from other types of ligamentous laxity and/or meniscal tears
Various methods delineate degree of damage and associated injuries
Knee may be treated symptomatically, followed by repeated evaluations over initial 2–3 weeks following injury.
Most active patients engaged in agility sports require surgical reconstruction.
Reconstruction is now usually delayed at least 3 weeks after injury to allow decrease in swelling and increase in range of motion.
For mild laxity with a firm endpoint (partial ACL injury) and no other associated injury, may treat with PRICES, functional rehabilitation, and protective bracing
Apparent partial injuries often progress to more obvious complete tears.
May attempt functional stabilization through rehabilitation, bracing, lifestyle modification; often requires surgical reconstruction
Posterior Cruciate Ligament (PCL)
Description: Tear of part or all of two major bundles of the PCL (posteromedial and anterolateral)
Mechanism of injury: Valgus/varus in full extension; in rare cases, severe twist; direct blow to the anterior proximal tibia, as in fall on artificial turf or other hard playing surface
Presentation: Usually less swelling than with ACL; otherwise, in acute stage, nothing particularly distinguishing; chronically, feeling of femur sliding anteriorly off tibia, particularly when rapidly decelerating or descending slopes or stairs
Examination: Acute, if produced by varus or valgus mechanism, may find abduction or adduction stress test positive in full extension; if produced by blow to anterior tibia, posterior drawer sign may be positive; chronic, rely on posterior drawer sign and gravity test (see Fig. 55.4 )
Imaging: Cross-table lateral view radiographs may show sag of tibia compared to opposite side; may accentuate by doing posterior drawer sign while taking cross-table lateral view; may see bony avulsion with tibial attachment of the PCL; MRI shows posterior cruciate well and may help confirm diagnosis and evaluate for other injuries (see Fig. 55.4 ).
Differential diagnosis: Most difficult is distinguishing posterior cruciate injury from posterolateral corner injury; posterior drawer sign and posterolateral drawer sign may appear the same. Both injuries may exist in same knee.
Treatment: Acute, most important to delineate degree of injury; may require examination under anesthesia and arthroscopy; for mild laxity (isolated PCL tear), may treat with PRICES, functional rehabilitation, protective bracing; for moderate or severe laxity, surgical repair/reconstruction is usually required
Chronic, may attempt functional stabilization through rehabilitation and bracing; often requires surgical reconstruction if instability is more than mild