8.1 History and examination of the knee

Traditionally, examination of a joint involves the principle ‘look, feel, move’, but for the knee the order and sequence of examination changes, depending on the likely diagnosis suggested by the history. The history is key in detecting the characteristic patterns of symptoms that will direct examination. Specific direct questions may be needed to aid this process. This is not asking ‘leading questions’ but is rather ‘direct questioning’ and this helps focus the patient’s mind onto the specific symptoms and the examiner onto specific possible diagnoses.

In addition, the level of disability caused by the symptoms as well as patient expectations need to to be carefully elicited as this will have a significant bearing on the management plan.

This chapter on history and examination of the knee breaks down the process into three parts: history, general knee examination, and targeted knee examination.

The three key features when addressing a patient with a knee problem are:

In principle, the site, nature, character, and severity of pain are determined by specific questions.

Swelling usually indicates that there is a significant problem in the knee.

This means the transient inability of the knee to go out straight rather than difficulty in flexing the knee. It is important to distinguish this from pseudo locking from the patellofemoral joint or following medial collateral injury where extension is limited by pain.

Giving way can also be described as buckling, not trusting the knee or giving out.

Other specific detail is required to lead to an action plan and these include:

After taking the history then there should be a fairly good idea of the diagnosis or, if not likely diagnoses, then the main category of problem.

Essentially the patient will be in one of five categories:

Examination starts with a general examination of the knee followed by specific examination to confirm a specific diagnosis that has been indicated by the history. The history and examination should lead to a management plan that may involve further targeted investigation or the initial stage of treatment.

General examination includes assessing the patient standing, walking, and lying supine, and includes active, passive, and provocative tests or movements. This should allow specific examination to concentrate on one of four areas (Box 8.1.2):

This includes general habitus, leg alignment, posture, change in alignment on walking, the presence of an antalgic hip gait, and muscle wasting. Looking at the leg starts as the patient walks in to the clinic and takes in to account their general demeanour, appearance, manner of walking, and mobility around the examination area. All these factors add information to the diagnostic equation.

Normal alignment, varus (bowlegged), or valgus (knock-kneed) alignment is noted and the presence of increasing deformity as a lateral or medial thrust on walking is also elicited (Figure 8.1.1).

Malalignment may also be rotational. Squinting patellae occur when the feet point forward but the knees squint towards each other representing abnormal femoral and tibial torsion. Isolated external tibial torsion may be noted if the patella points forward but the feet point outwards more than 10–15 degrees. There is clearly a wide range of what is normal and physiological varus or hyperextension, for example, may be a variant of normal.

Examination supine involves a combination of look, feel and move. In order to look properly we need to feel the knee aiming to detect and confirm specific appearances and problems.

Inspection of the patellofemoral joint is initially best performed with the patient sitting with the leg flexed over the edge of the couch, noting the following features or signs:

With the patient lying supine the following tests can be performed:

With the knee flexed at 90 degrees, the knee is further examined

This is best performed with the knee flexed at 90 degrees.

The following ligaments or ligament complexes can be examined individually or in combination and the pattern of instability determined:

Tenderness following acute injury is examined for with the knee at 90 degrees, applying deep palpation over the epicondyles and, for the medial collateral ligament, over the tibial attachment. Laxity and pain on stressing the collateral ligaments is detected at full hyperextension, 0 degrees extension and at 20–30 degrees with the purpose of detecting a difference with the other side. The patient should be asked whether the movement feels the same.

For detection of movement the knee is cupped by one hand using the fingers and the palm alternately as a fulcrum against the epicondyles, and the leg is levered to the side by firmly grasping the heel (Figure 8.1.7). Flexion beyond 20–30 degrees will result in rotation at the hip rather than opening of the knee.

Integrity of the lateral collateral ligament can be checked by palpation in the ‘figure four’ position, feeling the chord-like structure running from fibula head to femur.

To detect laxity of the ACL the patient needs to be relaxed to avoid involuntary contraction of the hamstrings. With appropriate techniques it is usually possible to reliably detect laxity in the awake patient.

This detects increased AP movement in the knee at 10–15 degrees flexion (Figure 8.1.8). Firm AP force is applied, pushing back with the thigh hand and pulling forward with the tibial hand.

Two differences are sought:

The pivot shift test is pathogmonic of ACL deficiency and reproduces the giving way instability sensation felt by the patient.

The test has a reputation as painful and difficult to perform but with adequate support of the leg it is painless and easily reproducible. The principle is to detect a jumping, or familiar buckling sensation, as the lateral tibia slides from its normal position articulating with the lateral femoral condyle into an abnormal anterior subluxed position, and vice versa, at around 20 degrees flexion on bending and straightening the knee.

Figure 8.1.9 shows how the tibia is supported, between the examiner’s side and over the examiner’s forearm. The hand is then interlocked over the wrist of the other hand, which is applied against the lateral aspect of the proximal tibia and fibula. This is an active test involving participation of the patient. Initially their confidence is obtained by asking them to flex their knee from extension without the examiner applying any force on the leg.

The examiner then flexes the knee passively by lifting from the patient’s posterior calf, exerting an anterior force on the tibia. In a positive test the tibia is felt to slide or jump posteriorly back into place as the knee bends. Conversely as the knee is straightened the tibia is felt to sublux anteriorly. This can be an obvious clunk or a subtle glide. To emphasize the test, looking for reproduction of the patient’s distrust of their knee, increasing load is applied, both in valgus and by inline compression, loading the lateral compartment to exaggerate the sliding of the femur over the dome of the lateral tibial plateau. When it is difficult for the patient to relax, the patient is asked to straighten their knee, thereby relaxing the hamstrings and allowing the pivot shift slide or clunk to be felt.

This test, in which the tibia is pulled anteriorly with the knee at 90 degrees (Figure 8.1.10), is much less reliable in the detection of ACL insufficiency. Paradoxically, it is very useful in detecting posterior sag and the step-off sign for posterior cruciate ligament insufficiency. The examiner sits against the foot and the palms grip the sides of the tibia exerting a strong anterior pull. The index fingers of both hands are used to ‘knock out’ posterior pull by the hamstrings.

The posterior cruciate ligament acts to resist posterior translation of the tibia. Laxity is best examined with the knee at 90 degrees.

When both knees are viewed from the side, any sagging back of the tibial tubercle and upper tibia is noted as posterior sag. A straight edge such as an x-ray packet (if available) may be useful to demonstrate subtle sag (Figure 8.1.11).

With the knee at 80–90 degrees the tibia is pushed posteriorly to detect any increased posterior translation.

This is perhaps the most useful sign in detecting posterior cruciate ligament laxity as it also helps to determine treatment. Figure 8.1.12 shows the three grades based on the stepping down from the tibia on to the femur. Grade II means the tibia is flush with the femur and when grade III is detected (tibia posterior to femur) there is likely to be injury to the posterolateral corner.

Increased posterior sag can also be detected at 15–20 degrees flexion when the tibia is pushed posteriorly in relation to the femur.

Injuries to structures of the posterolateral corner result in increased external rotation of the tibia on the femur.

The patient can be supine or prone (Figure 8.1.13), but prone is probably more accurate. The examiner externally rotates the supported feet while an assistant keeps the knees together to eliminate femoral rotation. Greater than 15 degrees ‘dialled’ external rotation indicates injury.

Increased external rotation at 30 degrees suggests an isolated posterolateral corner injury whilst increased external rotation at 30 and 90 degrees suggests injuries to both the posterolateral corner and posterior cruciate ligament.

With the knee at 90 degrees the knee is rotated by gripping the proximal tibiofibular joint and pushing it posteriorly in order to detect an increase in posterolateral mobility compared to the other side (Figure 8.1.14). Alternatively, with the patient sitting, the examiner spins out the tibia while the patient keeps their knees together (spin test). Increased posterolateral rotation can be noted by feeling and looking at the superior tibiofibular joint.

When the legs are picked up by the big toe or forefoot then the knees fall into external rotation as the knee goes into hyperextension (Figure 8.1.15) when the posterolateral corner is stretched out.

This test detects the opposite of the pivot shift phenomenon. The knee is supported in flexion with the foot externally rotated and the knee in compression and valgus. On moving into extension the lateral compartment reduces under the femur with a clunk. This is a difficult test to perform reliably.

Injury to the posterior oblique ligament of the posteromedial corner is present when instability to valgus stress is present with the knee in full extension. In this situation injury to one or both cruciate ligaments should be suspected.

The hallmark signs when examining for joint surface damage are signs associated with catching of worn articular cartilage surfaces. Fine crepitus on joint movement can be heard but it usually needs to be felt. Active movement loads the joint and the examiner places a hand over the moving part, either feeling with the fingers or the flat of the palm. Popping, snapping, or clunking may also be felt on movement under load and if painless are considered ‘safe’.

When two bare bone surfaces are forcibly compressed together then there is very high friction and the surfaces momentarily stick together before sliding in a juddering fashion. This sign has been described as the pepper mill sign for obvious reasons and can be felt in the medial and lateral compartments by carefully forcing the knee into varus or valgus and slowly moving the joint under compressive load. With pausing, the thin synovial fluid is being compressed out of the articulation removing any lubrication benefit.

Loss of flexion and or extension is an early sign of joint degeneration. For consistency and accuracy, flexion is best measured with the patient reclined nearly supine, keeping the quadriceps at maximum length.

When the knee is at 90 degrees the distal articular surface of the medial femoral condyle is facing distally and is not covered by the patella. Deep tenderness on palpation of this surface is consistent with articular surface damage.

Cysts and fullness in the popliteal fossa are best seen and palpated with the knee in extension and when standing.

History and examination are linked and specific examination is substantially determined by the likely diagnosis or group of diagnoses indicated by the history (Box 8.1.3). It is, however, important to undertake general examination of the knee with the patient, walking, standing, sitting and lying supine. Specific examination will then create a pattern of signs which should lead to definitive diagnosis (Table 8.1.1).