CHAPTER 11

KNEE

Précis of the Knee Assessment^*

History

Observation

Examination

Active movements

Knee flexion

Knee extension

Medial rotation of the tibia on the femur

Lateral rotation of the tibia on the femur

Patellar tracking

Passive movements (as in active movements)

Resisted isometric movements

Knee flexion

Knee extension

Ankle plantar flexion

Ankle dorsiflexion

Tests for ligament stability

Test for one-plane medial instability

Abduction (valgus stress) test

Hughston’s valgus stress test

Test for one-plane lateral instability

Adduction (varus stress) test

Hughston’s varus stress test

Tests for one-plane anterior and posterior instabilities

Posterior sag sign (gravity drawer test)

Godfrey (gravity) test

Lachman test

Drawer sign

Active drawer test

Tests for anteromedial and anterolateral rotary instabilities

Slocum test

Lateral pivot shift maneuver (test of MacIntosh)

Jerk test of Hughston

Slocum ALRI test

Crossover test of Arnold

Tests for posteromedial and posterolateral rotary instabilities

Hughston’s posteromedial drawer sign

Hughston’s posterolateral drawer sign

Posteromedial pivot shift

Jakob test (reverse pivot shift maneuver)

External rotation recurvatum test

Loomer’s posterolateral rotary instability test

Special tests

Tests for meniscus injury

McMurray test

Apley’s test

Bounce home test

Plica tests

Mediopatellar plica test

Hughston’s plica test

Tests for patellofemoral dysfunction

Clarke’s sign

McConnell test for chondromalacia patella

Tests for swelling

Brush, stroke, or bulge test

Indentation test

Fluctuation test

Patellar tap test (ballotable patella)

Other tests

Q-angle or patellofemoral angle

Fairbank’s apprehension test

Noble compression test

Functional leg length

Reflexes and cutaneous distribution

Joint play movements

Backward and forward movements of the tibia on the femur

Medial and lateral translations of the tibia on the femur

Medial and lateral displacements of the patella

Depression (distal movement) of the patella

Anterior movement of the fibula on the tibia

Palpation

Diagnostic imaging

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^*Although an examination of the knee may be performed with the patient in the supine position, some of the tests may require the patient to move to other positions (e.g., standing, lying, prone, sitting). When these tests are used, the examination should be planned so that movements (and therefore the patient’s discomfort) are kept to a minimum. The sequence should proceed from standing, to sitting, to supine lying, to side lying, and finally to prone lying. After any examination, the patient should be warned that the assessment may result in an exacerbation of symptoms.

SELECTED MOVEMENTS

ACTIVE MOVEMENTS^1,2

GENERAL INFORMATION

During the active movements of the knee, the examiner should observe (1) the excursion of the patella, to make sure it tracks freely and smoothly; (2) the range of motion (ROM) available in the tibiofemoral and patellofemoral joints; (3) whether pain occurs during the movement, and if so, where and when; and (4) what appears to be limiting the movement. The active movements may be performed in the sitting or supine position; as always, the most painful movements should be done last, and the unaffected side is tested first.

PATIENT POSITION

The patient is supine or sitting

EXAMINER POSITION

The examiner stands to the side of the patient to instruct the person and observe the ROM.

Flexion

TEST PROCEDURE

The patient is asked to flex the knee as far as possible.

INDICATIONS OF A POSITIVE TEST

Full knee flexion is 135º (0º being a straight knee). If the range of movement is less than this or is less than in the unaffected leg, the test result is positive. As the patient moves the knee through flexion and extension, the examiner should watch the movement of the patella as it “tracks” along the femoral trochlea. The examiner should note whether the movement is smooth from beginning to end or whether the patella shows a lag or abrupt jump as it attempts to center in the groove. The patella does not follow a straight path as the knee moves from extension to flexion. Normally, it follows a curved pattern, moving medially in early flexion and then laterally.

Extension

TEST PROCEDURE

The patient is asked to extend the knee.

INDICATIONS OF A POSITIVE TEST

Active knee extension is approximately 0º but may be −15º, especially in women, who are more likely to have hyperextended knees (genu recurvatum). If the range of movement is less than this or is less than in the unaffected leg, the test result is positive. The knee extensor muscles develop the greatest force near 60º, and the knee flexor muscles develop their greatest force between 45º and 10º. To complete the last 15º of knee extension, a 60% increase in the force of the quadriceps muscles is required. Therefore, the examiner should watch for evidence of quadriceps lag, which means the quadriceps muscles are not strong enough to fully extend the knee. The lag results from loss of mechanical advantage, muscle atrophy, decreasing power of the muscle as it shortens, adhesion formation, effusion, or reflex inhibition that results in instability of the knee.

PATELLAR MOBILITY^3,4

PURPOSE

To assess the mobility of the patella.

SUSPECTED INJURY

Patellofemoral dysfunction

PATIENT POSITION

The patient is sitting or supine.

EXAMINER POSITION

The examiner is positioned directly adjacent to the knee to be tested.

TEST PROCEDURE

The examiner’s hands are placed near the knee to stabilize the tibia and femur. The thumbs of the hands are placed on the side (either medial or lateral) of the patella. The examiner passively glides the patella medially and laterally. The amount, quality, and symptomology of the motion are noted. The side-to-side passive motion of the patella also should be tested in 45° of flexion; this is a more functional position and gives a better indication of the functional stability of the patella.

INDICATIONS OF A POSITIVE TEST

Normally, the patella should move up to half its width medially and laterally in extension. The end feel of these movements is tissue stretch. Lateral displacement must be performed with care, especially in patients who have experienced a dislocated patella.

CLINICAL NOTE/CAUTION

• When the patella is pushed medially or laterally, the examiner should note whether it stays parallel to the femoral condyles or tilts or rotates. For example, if the patella is pushed medially when the medial structures are tight, the lateral border of the patella tilts up. Likewise, with tight lateral structures, the medial border tilts up. If the lateral structures are tight superiorly, the inferior pole of the patella medially rotates. These are examples of dynamic tilt and rotation problems of the patella.

RELIABILITY/SPECIFICITY/SENSITIVITY

Unknown

SPECIAL TESTS FOR ONE-PLANE MEDIAL INSTABILITY

Relevant Special Tests

Abduction (valgus stress) test

Hughston’s valgus stress test

Definition

Sudden or violent shearing of the tibiofemoral joint can result in stretching or tearing of the tibial (medial) collateral ligament (MCL/TCL) and other, associated ligaments. The shear or excessive force causes the tibia to move away from the femur (i.e., gap) on the medial side.

Suspected Injury

Structures that may have been injured include:

Tibial collateral ligament (superficial and deep fibers)

Posterior oblique ligament

Posteromedial capsule

Anterior cruciate ligament

Posterior cruciate ligament

Medial quadriceps expansion

Semimembranosus muscle

Note: The structures damaged and the degree of injury depend on the forces applied. The more structures damaged, the more unstable the knee

Epidemiology and Demographics

The exact prevalence of MCL/TCL injuries in the general population is unknown. It is the most common ligament injury. The MCL/TCL often is injured in conjunction with other structures, such as the anterior cruciate ligament or medial meniscus.⁵

Relevant History

The patient may report a previous history of a knee injury that has affected the mechanics of the knee. Previous injuries to the ankle or hip also may predispose a person to increased stresses at the knee.

Relevant Signs and Symptoms

• Mild to moderate knee pain is present.

• The patient reports feeling a tearing in the knee, not a “pop.”

• Bruising in the medial knee often is present, because the MCL/TCL is an extra-articular structure.

• Swelling builds up slowly over several days.

• The patient walks with a limp and has pain on knee extension, because extension stretches the ligament.

• Instability and “giving way” may be noted.

• Loss of knee motion and moderate stiffness may be present.

• Medial joint line pain or pain where the ligament attaches to the femur or tibia may be reported.

Mechanism of Injury

The MCL/TCL functions to restrain valgus stress and lateral rotation of the tibia. A blow to the outside of the knee most commonly injures the ligament. Contact injuries involving direct valgus loading to the knee are the usual mechanism in a complete tear. Noncontact, or indirect, injuries occur with deceleration, cutting, and pivoting motions. Anatomically, the MCL/TCL is composed of two layers, the superficial layer and the deep layer; the deep layers attach to the medial meniscus.

Avulsion of ligaments generally occurs between the unmineralized and mineralized fibrocartilage layers. MCL/TCL injury occurs most often at the femoral attachment (65% of cases).6–11

ABDUCTION (VALGUS STRESS) TEST^12,13

PURPOSE

To assess for one-plane (straight) medial instability, which means that the tibia moves away from the femur (i.e., gaps) on the medial side.

SUSPECTED INJURY

Structures that may have been injured include:

Medial collateral ligament (superficial and deep fibers)

Posterior oblique ligament

Posteromedial capsule

Anterior cruciate ligament

Posterior cruciate ligament

Medial quadriceps expansion

Semimembranosus muscle

PATIENT POSITION

The patient is supine with the test knee in extension.

EXAMINER POSITION

The examiner stands adjacent to the lateral aspect of the knee.

TEST PROCEDURE

The unaffected knee is tested first. One of the examiner’s hands grasps the patient’s ankle, and the other hand supports the lateral aspect of the knee joint. The examiner applies a valgus stress at the knee (pushes the knee medially) while the ankle is stabilized in slight lateral rotation either with the hand or with the leg held between the examiner’s arm and trunk. The knee is tested first in full extension and then in slight flexion (20° to 30°) so that it is “unlocked.” The two legs are compared.

INDICATIONS OF A POSITIVE TEST

A positive test result is indicated if the tibia moves away from the femur excessively when a valgus stress is applied with the knee in extension. The normal abrupt end feel is lost with a positive test result. Increased gapping with the knee in extension indicates injury to the medial collateral ligament and the anterior cruciate ligament. Increased gapping with the knee slightly flexed indicates injury primarily to the medial collateral ligament. If the test result is positive when the knee is flexed to 20° to 30°, structures that may have been injured include:

• Medial collateral ligament

• Posterior oblique ligament

• Posterior cruciate ligament

• Posteromedial capsule

CLINICAL NOTES

• A positive test result on full extension is classified as a major disruption of the knee. The examiner usually finds that one or more of the rotary tests also produce a positive result.

• If the examiner applies lateral rotation to the foot when performing the test in extension and finds excessive lateral rotation on the affected side, this is a sign of possible anteromedial rotary instability.

• The flexed part of the valgus stress test is considered the true test for one-plane medial instability, because the cruciates are eliminated.

RELIABILITY/SPECIFICITY/SENSITIVITY¹³

Reliability (interrater range): k = 0.01-0.38

HUGHSTON’S VALGUS STRESS TEST¹²

PURPOSE

To assess for one-plane (straight) medial instability.

SUSPECTED INJURY

Structures that may have been injured include:

Medial collateral ligament (superficial and deep fibers)

Posterior oblique ligament

Posteromedial capsule

Anterior cruciate ligament

Posterior cruciate ligament

Medial quadriceps expansion

Semimembranosus muscle

PATIENT POSITION

The patient is supine with the test knee in extension.

EXAMINER POSITION

The examiner stands adjacent to the lateral aspect of the knee.

TEST PROCEDURE

The normal knee is tested first. One of the examiner’s hands grasps the patient’s big toe, and the other hand supports the lateral aspect of the knee joint. Facing the patient’s foot, the examiner abducts the hip so that the thigh lies on the plinth but the lower leg is free. The examiner grasps the patient’s big toe and applies a valgus stress, allowing any natural rotation of the tibia. The two legs are compared.

INDICATIONS OF A POSITIVE TEST

A positive test result is indicated if the tibia moves away from the femur excessively when a valgus stress is applied with the knee in extension, and the end feel is changed. The structures tested are the same as in the abduction (valgus) stress test.

CLINICAL NOTE

• Doing the test with the thigh resting on the plinth often allows the patient to relax more and is less likely to lead to muscle spasm, which may limit movement.

RELIABILITY/SPECIFICITY/SENSITIVITY

Unknown

SPECIAL TESTS FOR ONE-PLANE LATERAL INSTABILITY

Relevant Special Tests

Adduction (varus stress) test

Hughston’s varus stress test (see Hughston’s valgus stress test)

Definition

Sudden or violent shearing of the tibiofemoral joint can result in stretching or tearing of the lateral (fibular) collateral ligament (LCL/FCL) and other, associated ligaments. The shear or excessive force causes the tibia to move away from the femur (i.e., gap) on the lateral side.

Suspected Injury

Structures that may have been injured include:

Fibular or lateral collateral ligament

Posterolateral capsule

Arcuate-popliteus complex

Biceps femoris tendon

Posterior cruciate ligament

Anterior cruciate ligament

Lateral gastrocnemius muscle

Iliotibial band

Peroneal nerve

Epidemiology and Demographics

Injury to the LCL/FCL is the least common knee ligament injury. Injuries to the LCL/FCL are rare, accounting for only 2% of all knee injuries. The LCL/FCL is the least likely knee ligament to be sprained, because most LCL/FCL injuries are caused by a blow to the inside of the knee, and that area usually is shielded by the opposite leg.^6,7,9–11

Relevant History

The patient may report a previous history of a knee injury that has affected the mechanics of the knee. Previous injuries to the ankle or hip may also predispose the patient to increased stresses at the knee.

Relevant Signs and Symptoms

• Mild to moderate knee pain is present.

• The patient may report feeling a pop in the knee.

• Loss of knee motion and moderate stiffness are present.

• Lateral joint line pain may be reported.

• Bruising in the lateral knee often is present, because the LCL/FCL is an extra-articular structure.

• Swelling builds up slowly over several days.

• Instability and giving way may be noted.

Mechanism of Injury

The LCL/FCL functions to control varus loading and lateral rotation of the tibia running from the femoral condyle to the head of the fibula. Contact injuries involve a direct varus load to the knee; this is the usual mechanism in a complete tear. The most common method of injury is a direct varus force with the foot plantar flexed and the knee in extension. Related injuries include injuries to the peroneal nerve, posterolateral capsule damage, or posterior cruciate ligament damage. The mechanism of knee adduction, flexion, and lateral rotation of the femur on the tibia is a much less common mechanism.

With excessive force, the LCL/FCL usually is disrupted initially, followed by the capsular ligaments, the arcuate ligament complex, the popliteus, the iliotibial band, the biceps femoris, and the common peroneal nerve; one or both cruciate ligaments may be disrupted.

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