Physical examination of the knee begins with inspection, and palpation followed by active and passive mobilisation of the joint and isometric muscle testing. Finally, specific tests tailored for the function of the knee are performed to form a diagnosis. Neurovascular examination is recommended to ascertain any injuries to the nerves, arteries and veins.
Anatomical landmarks represent a guide in the examination of the specific region of the body that may be compromised by injury or degenerative conditions.
Relative to the knee, the examiner focuses on protruding surfaces of the joint such as the knee cap or patella, epicondyles, joint lines, tibial plateau, tibial tuberosity and proximal fibula and the muscles and tendons surrounding the knee.
These landmarks are easy to identify during a medical examination.
For the initial inspection, the patient is in a standing position facing the examiner with minimal clothing and no shoes. The examiner aims to detect any changes in appearance and load axis of the leg such as:
Varus knees (“O” shape)
Valgus knees (“X” shape)
Leg length discrepancy relative to the pelvis
With the patient standing laterally the examiner investigates:
Knee flexion deformity (inability to extend fully)
Recurvatum deformity (knee hyperextension)
Additional criteria for inspection are:
Inability to stand
Palpation of the different areas of the knee helps identifying:
Knee joint stiffness
Structural injuries to the patella, distal femur, tibia, muscles, tendons and ligaments
Changes in patella mobility
Thickened synovial membrane
Strength of quadriceps and hamstrings
Changes in patella mobility
Thickened synovial membrane
Strength of quadriceps and hamstrings
Range of movement
To evaluate the function of the knee, the patient is asked to actively perform some tasks to assess changes in the range of movement, joint instability and level of pain. During the examination it is critical to monitor the non-injured side of the body to achieve an overall functional status of the patient. If abnormalities are detected, the examiner will perform passive tests to measure increased or impaired range of movements; however without causing pain.Subsequently, specific instability tests will follow to identify the exact underlying pathology.
To begin with the examination, the patient is asked to actively perform the following actions:
Small knee bend
Sit to stand
Active mobilisation of the knee
Active mobilisation of the knee is used to examine the range of motion, ease of motion, level of pain, noises such as crepitus, and abnormality in the movement of the patella (lateralisation).
The patient is asked to fully extend and flex the knee. The examiner observes possible muscle weakness and changes in joint flexibility. The normal range of movement is subjective for each individual but it should include a full extension at 0º.
The flexion of the knee should range between 110º up to 140º. The affected knee is always compared to the contralateral side. With lack of full knee extension an extension deficit is diagnosed. On the contrary, an extension beyond normal indicates a hyperextension.
The term fixed flexion is used if an extension deficit is detected without being able to extend the leg passively.
Subsequently, the range of motion of the knee is assessed with the patient in a lying position and measured with a goniometer. The examination is performed by taking as reference points the great trochanter of the hip, the lateral knee line and the lateral malleolus of the ankle:
Full extension at 0º
Full flexion at 110º - 140º
Passive mobilisation of the knee
Passive mobilisation of the knee is mostly performed with the patient in a lying position. The examiner moves the lower extremity in various planes with flexion and extension to determine changes in the range of motion, fluidity, pain, crepitus, and patella lateralisation.
The range of rotation in passive movement of the knee can be larger compared to active rotation.
Rotation in the knee is assessed with the knee flexed to exclude hip rotations.
Isometric muscle test
This test reveals any muscular deficits of the lower limb other than the strength itself. The examiner focuses on pain, avulsion and rupture of the quadriceps, biceps femoris, semimembranosus, semitendinosus, sartorius, gastrocnemiusmuscles.
The patient sits at the edge of the bed with both knees at 90º flexion to the next end and flex the knee against the resistance of the examiner keeping the ankle firmly stable.
While contracting the leg muscles the patient is asked to resist flexion and extension against the examiner’s force.
Palpation of these muscles during the test determines the presence of pain and ruptures.
Muscle strength test
To measure muscle strength the patient is asked to flex/extend the knee against the resistance of the examiner. Muscle strength is categorised as follows:
Grade 0: no contraction
Grade 1: small contraction
Grade 2: movement, but not against gravity
Grade 3: movement against gravity
Grade 4: movement against resistance
Grade 5: no detectable weakness
Leg muscle atrophy is diagnosed by measuring the distal upper leg circumference at15 and 10 cm proximally and 10 and 15 cm distally to the midline of the patella.
Muscular abnormality can arise as a consequence of inactivity, change in gait, soft tissue injury and neurological diseases.
Gait analysis determines functional changes on the gait cycle. Nowadays gait analysis can be performed with 3D technology enhanced with a computerised software to deliver a precise, objective measurement of various biomechanic parameters.
To begin with the 3D motion test, multiple marker-sets are applied on pre-defined skeletal structures of the pelvis and lower limbs.
While the patient is walking on the treadmill, infrared video cameras capture the markers' movement that is recorded to create a 3D motion sequence. A specific software allows to accurately measure the gait patterns in all three dimensions. This includes:
Step and stride length
Knee flexion and extension
Medio lateral stability
Meniscal tears are very frequent.They trigger pain, joint line tenderness and effusion, either medially or laterally particularly due to meniscal subluxation. Such symptoms are worsened when flexing, rotating and loading the knee.
This is the most common and reliable test for meniscal tears. The examiner palpates the anterior or posterior joint line and tenderness is felt with a meniscal tear. If during this procedure the pain radiates in either the proximal or distal line, it may indicate a pathology of the collateral ligament instead of the meniscus.
Resilient extension deficit
A resilient extension deficit occurs when a fragment of the damaged meniscus luxates, thus impeding the full extension of the knee. This symptom is often the result of a bucket handle rupture of the meniscus.
McMurray test for meniscal tear
This test is used for the diagnosisof a meniscal tear. With the patient in either a supine or dorsal decubitusposition, the examiner grasps and palpates the knee with one hand while theother holds the foot to gently move the knee joint passively in a range ofmovements.
The examiner applies a valgusstress, while simultaneously rotating externally the leg and extending theknee. With a tear of the medialmeniscus this action results in pain and anaudible clunk.
To test for the lateral meniscus, the same manoeuvre is repeated with a varus stress to the knee and medial rotation to the tibia before applying the full extension of the knee.
This test is also used for the diagnosis of meniscal tears and begins with the patient lying in a prone position.
The examiner passively flexes the knee at 90º and compresses or distracts the heel while rotating the knee medially and laterally. The test is positive for meniscal tear when the combination of compression and rotation is more painful or results in a reduced rotation compared to normal. Conversely, if pain arises from distraction/rotation, the condition is most likely due to ligament problems.
Thessaly test for meniscal tear
To begin with the test, the patient stands on the leg under examination with the knee bent to a 20º flexion while keeping the opposite leg flexed and elevated behind. The patient may need to hold the examiner’s hands for balance. During the test, the patient rotates the knee medially and laterally three times. The test is positive when the patient feels discomfort on the outer line of the knee, or when a knee locking/catching occurs.
Ege’s test for meniscal tear
Also called weight bearing McMurray’s, this test is used to assess the rupture of the medial and lateral menisci.
The patient stands with the feet 30 to 40 cm apart while keeping the knee at either maximal external rotation (medial meniscus) or maximal internal rotation(lateral meniscus).
When examining the medial meniscus, the patient squads with full external rotation of the knees and slowly raises.
Subsequently, a limited squad is repeated with the knee in maximal internal rotation for the lateral meniscus.
The test is positive when this manoeuvre triggers pain along the corresponding kneejoint line of the affected meniscus or produces an audible click.
Neurovascular examination is required to determine any underlying pathologies of the nervous system and the vascular system of the lower limbs. It comprises the assessment of muscle atrophy and strength, skin sensitivity, and pulses of the lower limbs.
With significant traumatic injuries to the knee, the vascular system may be compromised. To ascertain that the lower limbs receive sufficient blood perfusion the examiner performs the following tests:
peripheral pulses to the dorsal pedal artery, and the tibialis posterior artery
capillary refill (normal refill time <2 seconds)
Neurological tests: Reflexes
If the examiner has identified functional deficits of the muscles in the lower limb, a further neurological testing is required to determine possible neurological pathologies to the spine. Below is the list of tests performed during the neurological examination:
Skin temperature throughout the lower limb
Numbness and/or needle sensation
Reflexes- Patella ligament (L3/L4) and Achilles tendon (S1/S2)
Dermatomes- L1 to S4
L2 -hip flexion
L3 -knee extension
L5 -big toe extension OR 4 lesser toes extension
L5/S1- knee flexion
S1 -plantar flexion OR foot eversion
S2 -toe flexion
Furthermore, the examiner has to ascertain whether bladder or
bowel problems are present e.g.incontinence.
Assessing paraplegia and tetraplegia
The level of paralysis is based on the ASIA Impairment Scale of The American Spinal Cord Injury Association. In order to help classify differing degrees of spinal cord injury, the ASIA impairment scale is used to compare and understand residual function.
A - Complete: No motor or sensory function in the lowest sacral segment (S4-S5)
B - Incomplete Sensory function below neurologic level and in S4-S5, no motor function below neurologic level
C - Incomplete Motor function is preserved below neurologic level and more than half of the key muscle groups have a muscle grade less than 3
D - Incomplete Motor function is preserved below neurologic level and at least half of the key muscle groups below neurologic level have a muscle grade 3
E - Normal Sensory and motor function.
Levels of paralysis
Methods to define the level of the paralysis:
Biceps jerk C5 /C6
Supinator jerk C6
Extensor digitorum reflex C7
Triceps jerk C7/ C8
Abdominal reflex T8-T12
Knee jerk L2 / L4
Ankle jerk L5 / S1 / S2
Bulbo-spongiosus reflex S2-S4
Anal reflex S5
Plantar reflex L5-S
Postero-lateral Drawer Test
In this test the patient is in a supine position with the hip flexed at 45º and the knee at 80º. The examiner externally rotates the tibia at 15º while applying pressure posteriorly to the tibia just below the knee. The test is positive for PCL pathology if the lateral tibial plateau rotates externally relative to the femur and the patient feels no firm stop.
Reversed pivot shift test
This test is used to assess a posterior cruciate ligament (PCL) deficiency. The patient lies in a supine position with the knee flexed at 90º. The examiner holds the ankle with one hand and the other one at the lateral aspect of the tibia just below the knee. The examiner then applies a valgus stress and an axial load while internally rotating the tibia as the knee is flexed from a fully extended position. The test is positive for PCL pathology if subluxation of the tibia occurs while the femur rotates externally followed by a reduction of the tibia at 30-40º degrees of flexion.
Quadriceps active test
This test is applied to assess the posterior cruciate ligament (PCL) integrity. The patient lies supine with the test leg flexed at 80-90º. The examiner pushes the ankle firmly grounded and asks the patient to contract the quadriceps muscle. With a healthy knee there is no joint movement. In contrast, with a PCL tear, the patella and patellar tendon are pulled, ultimately resulting in a forward shift of the tibia.
Varus Trust Gait
This simple a test whereby the examiner observes the patient walking and assesses whether a varus deformity occurs during the stance phase.
Quadriceps angle or Q angle
The Q angle is an imaginary angle formed by the line beginning at the anterior superior iliac spine of the pelvis to the midpoint of the patella. The Q angle is a parameter of reference to assess various pathologies and is measured mostly in a standing position. It is normally in the range of 10º and 15º and is reduced during knee flexion. The increase in lateral movement of the patella and consequently of the Q angle occurs with femoral anteversion, external tibial torsion, increased valgus load axis or lateral position of tibial tuberosity.
Patellar instability – dislocation
The patella is stabilised by the femoral trochlea (patellofemoral grove) and the medial retinaculum. A patellar dislocation occurs when these structures present abnormalities. If the examiner feels the patella moving laterally from its normal anatomical position, it indicates a patellar dislocation. The patient may feel pain on the patella caused by the rupture of the medial retinaculum, intraarticular bleeding/effusion or injuries to the bony lateral restrains.
Patellofemoral joint testing
This test is used for the diagnosis of patellofemoral pathology. Normally the patella is stabilised by the femoral trochlea and the medial retinaculum. In case of pathology, the patella luxates laterally pushed by the quadriceps muscle and patellar tendon, creating significant pressure on the cartilage of the patellofemoral joint and pain sensation. Often these symptoms arise with quadriceps atrophy. When the examiner palpates the cartilage on both sides of the patella pain is elicited.
Patellar subluxation test - Apprehension Test
This test is used for the diagnosis of lateral patellar instability. The patient lies in supine position with the knee flexed at 20º. The examiner applies a gentle force lateral to the medial side of the patella. The test is positive when the patient experiences a quadriceps spasm and pain when close to subluxation.
Steinman test for meniscal tear
This test is useful to distinguish a meniscal tear from ligament injuries. The patient lies on a supine position or sits at the bed edge with the knee at 90º flexion. The examiner rotates the knee laterally and medially. The test is positive when pain is felt laterally with medial rotation or medial lateral rotation. The second component of the test is useful to distinguish a meniscal tear from a meniscal pathology. The examiner palpates the knee during flexion.
The test is positive when the pain elicited migrates towards the posterior side of the knee with increasing flexion.
The test is repeated with the knee extending and is positive if the pain moves anteriorly during the extension.
Haemarthrosis (bleeding into joint spaces) is mostly present in acute injuries of the knee.This may limit knee flexion, whereas tears to the anterior crucial ligament(ACL) fibres can mechanically prevent full extension.
This test is used to assess anterior crucial ligament (ACL) laxity and anterior knee instability. The patient lies supine with the knee flexed at 30º. The examiner stabilises the femur by placing the thumb above the patella and the other fingers behind the thigh. With the other hand the examiner grasps the tibia below the patella then pulls the lower leg forward. The degree of laxity of the femur and the tibia relative to one another is determined.
These are the criteria to establish ACL injuries with Lachman test:
Intact ACL: No anterior translation and a firm blockage of the joint
1+ laxity: tibia anterior translation of 0 to 5 mm
2+ laxity: tibia anterior translation of 5 to 10 mm
3+ laxity: tibia anterior translation over 10 mm
Pivot shift test
This is a test to assess the anterolateral rotary stability of the knee.
The patient is in a supine position with legs relaxed. With one hand the examiner grasps the ankle of the tested knee from the inner side and with the other the external side below the knee. The knee is gently flexed. Then a valgus and internal rotational load to the knee is applied while the knee is extended and the foot is firmly held against the examiner.
The test is positive when it causes an anterior sliding or clunk noise of the lateral tibia. In a healthy knee the anterior subluxation is blocked by theACL.
Anterior drawer test
This test is used to assess the integrity of the anterior cruciate ligament (ACL). The patient lies in a supine position keeping the hip of the tested knee flexed at 45º. The examiner holds the knee in 90º flexion and stabilises the leg. With the patient relaxed, the examiner pulls the tibia by applying a gentle force.
These are the criteria to establish ACL injuries with anterior drawer test:
Intact ACL: No anterior translation and a firm blockage of the joint
1+ laxity: tibial anterior translation of 0 to 5 mm
2+ laxity: tibial anterior translation of 5 to10 mm
3+ laxity: tibial anterior translation over 10 mm
Posterior Drawer Test
This test is used to assess posterior instability of the knee and the integrity of the posterior cruciate ligament (PCL). The posterior drawer test applies the opposite load described in the anterior drawer test. The patient lies supine with the knee flexed at 90º in neutral rotation and the hip at 45º. The examiner applies a posterior load on the tibia just below the knee. The test is positive when the tibia shifts posteriorly relative to the femur, indicating damage to the PCL.
Gravity sign or Tibial step of sign
The patient lies in a supine position while the examiner passively flexes both hips and knees to 90º and pushes the feet towards the patient’s chest.
If a posterior cruciate ligament pathology is present, the gravitational force applied to the knee will cause a posterior subluxation of the tibia relative to the femur orientation.
In addition, the tibial tuberosity becomes less prominent. Comparison with the contralateral knee is always recommended.
Medial instability – Medial Collateral Ligament - Valgus stress test
Injuries to the medial collateral ligament (MCL) may cause local laceration, ecchymosis and swelling.
During the valgus stress test, the patient lies in a supine position while the examiner holds the knee in 30º flexion placing one hand on the lateral side of the knee and the other on the ankle. Then the examiner moves the foot outwards (knee abduction). The test is positive if the test elicits pain, instability and joint laxity with an increased gap.
MCL injuries are classified as:
Grade I: Pain but no swelling or instability
Grade II: Pain, evident swelling, small laxity (5-10 mm) with a firm end feel
Grade III: Laxity over 10 mm, no end feel.
Lateral instability – Lateral Collateral Ligament – Varus stress test
Prior to the testing the integrity of the lateral collateral ligament (LCL), the examiner looks for local laceration, ecchymosis, or swelling.
To begin the varus stress test, the patient lies in a supine position with the legs straight. The examiner stabilises the ankle and then adducts the knee by applying a force medial to lateral.
The test is performed with straight legs and repeated with the knee flexed at 30º.
With a healthy knee, the cruciate ligaments restrain for a varus stress. The test is positive when it elicits pain at the LCL or when a joint line gap appears causing increased motion.
The injuries to LCL are classified as:
Lateral collateral ligament injury classification
Grade I – 0-5 mm of joint opening, no instability
Grade II – 5-10 mm of joint opening, mild instability
Grade III – 10-15 mm of joint opening, moderate instability
Grade IV – >15 mm of joint opening, severe instability