Examination of the Knee

Fig. 1.1

Assessing coronal plane. Note the physiological valgus attitude of the lower limb

Examination with the patient facing the examiner: assessing for varus or valgus posture and the presence of tibial bowing. Further coronal assessment can be performed from behind, whilst assessing for popliteal masses or scars. Varus and valgus deformities are often more obvious from behind.

Axial plane

This can also be assessed with the patient facing the examiner. Specific findings include a “squinting” (inward-tilting) patella [2], femoral anteversion or retroversion. Further assessment of axial (rotational) alignment can be performed in the case of patellofemoral instability using the “Staheli profile” technique with the patient seated [3].

Sagittal plane (Fig. 1.2)

Fig. 1.2

(a) Assessing left lateral sagittal plane. (b) Assessing right lateral sagittal plane

The patient is examined from the side assessing for flexed posture, and anterior tibial or femoral bowing.

1.2.1.2 Assessment of Gait

Full gait assessment is beyond the scope of this chapter. However, specifically with regards to orthopaedic knee examination, gait should again be assessed in coronal (frontal) and sagittal planes:

Coronal

Assess varus thrust for lateral collateral and posterolateral corner injury. Valgus thrust indicates medial collateral injury.

Sagittal

From the side, assess for flexed knee gait (suggesting fixed flexion of the knee or hamstring tightness) or back knee gait (suggesting hyperextension of the knee).

1.2.2 Examination of Knee with Patient Sitting on Couch, Legs Suspended from Side of Couch (Fig. 1.3)

Fig. 1.3

Examination of knee with patient sitting on couch, legs suspended from side of couch

It is the senior author’s practice to examine patellofemoral tracking before laying the patient supine to order to avoid “forgetting” the patellofemoral joint.

The patient is asked to sit on the side of the couch with legs hanging down but not touching the floor. The examiner then faces the patient and asks the patient to slowly flex and extend each knee in turn. This allows assessment of:

(a)

The extensor mechanism.
(b)

Patellar tracking (Video 1.1): The arc of interest is mainly between 70° of flexion and full extension.

Pathology most commonly detected includes:

“Inverse J sign” – lateral subluxation of the patella between 30° of flexion and full extension.
Frank lateral dislocation of the patella. This most commonly occurs in chronic recurrent patellar dislocation in near extension. However, it can occur with the knee flexed.

1.2.3 Examination Supine (Fig. 1.4)

Fig. 1.4

Assessing whilst supine on a couch. Note the valgus attitude is more obvious whilst supine

The patient is laid on the couch. Convention dictates that the patient should be fully supine in order to examine the hip joint first. However, examination of the knee is more comfortable with the patient in the semi-supine position (approximately 45° flexed at waist). The key to supine examination is to ensure patient relaxation, by avoiding causing unexpected pain. The best way to assess for pain is to consistently look at the patient’s eyes.

Alignment should be checked again from the end of the bed.

Muscle wasting

The quadriceps group, in particular vastus medialis obliqus (VMO). VMO wasting is often best detected by palpation of the muscle belly whilst asking the patient to contract the quads group. “Push your knee down into the bed”. Objectively, the quads can be assessed by measuring circumference of the thigh from a fixed bony point (e.g. 10 cm proximal to the tibial tubercle).

1.3 Feel

1.3.1 Warmth

Warmth is best palpated with the back of the examiner’s hand. If there is warmth, is there a focus e.g. prepatellar bursa, tibial or femoral component of a total knee replacement?

1.3.1.1 Effusion

There are three grades of effusion:

Grade 1: Small effusion: Best assessed by the “sweep” test. Fluid is gently moved from the lateral gutter by “sweeping” the hand over the gutter, into the medial gutter. The medial gutter is then pressed and the fluid is displaced back into the lateral gutter in a positive test.
Grade 2: Patellar tap: A moderate sized effusion will lead to the patella floating up towards the skin. The patella can then be “tapped” against the femoral trochlea.
Grade 3: Cross fluctuance: A very large effusion will lead to a fluid thrill demonstrated by cross fluctuance of the fluid when pressed.

1.3.1.2 Joint Palpation

The joint line is best palpated with the knee flexed to 80°. The examiner should visualise the anatomy being palpated through the skin and sequence of palpation should be consistent:

1.

Medial joint line: medial meniscus, medial femoral condyle, and tibial and femoral insertions of the medial collateral ligament (MCL). If a thickened medial plica is suspected, this can be palpated over the medial femoral condyle with the knee at 30°. More distally, the pes anserinus bursa should be palpated for tenderness typical of pes bursitis.
2.

Lateral joint line: lateral meniscus, lateral femoral condyle, and lateral collateral ligament. The fibula can also be palpated for tenderness and the superior tibiofibular joint can be balloted if instability is suspected.
3.

Popliteal fossa for popliteal cyst, and to exclude popliteal aneurysm.

1.4 Move

With the knee extended, the patient is asked to dorsiflex the ankle and lift the leg up straight. If there is any flexion when this is done, there are two possibilities:

(a)

Fixed flexion deficit due to joint contracture
(b)

Quadriceps weakness/extensor lag

In order to distinguish between the two, the patient is asked to rest the leg relaxed into the examiner’s hand. If full extension occurs, then there is a weakness of the quadriceps, known as extensor lag (Video 1.2). If the knee stays flexed, then there is fixed flexion.

Once this is performed, the patient is asked to flex the knee – “pull your heel towards your buttock”. Active flexion is assessed first. If there is full active flexion, then no passive assessment is required. If there is any deficit, the heel can be gently held and the knee flexed further always watching the patient’s face for pain.

It is important to note that full extension is termed as “zero degrees flexion”, a right angle is “90° flexion” and full flexion will depend on the body habitus of the patient and can vary from 120° in a patient with large thighs to 160° in a very thin patient. Another way to quantifying flexion deficit between knees is to determine the “heel to buttock” distance.

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