Knee Examination
Purpose
A systematic clinical examination guide for medical students and clinicians
Comparison
Compare both limbs when assessing:
- ROM
- Laxity
- Neurovascular
Exposure
From the mid-thigh to the toes. Remove shoes and socks.
Colour codes
- Required for undergraduates
- Clinical practice & postgraduate examination
Sequence
Standing → sitting with knees flexed to 90° → supine with the knee extended → supine with the knee at 90° → ligament and meniscal tests at the required angles → prone → standing functional assessment when safe.
Introduction
| Items | Clinical tips |
|---|---|
| W — Wash your hands. I — Introduce yourself, explain the examination and obtain consent. P — Ask about pain and identify its location before touching the knee. E — Expose both lower limbs appropriately and maintain dignity. | Ask: “Before I start, do you have any knee pain?” If present, ask the patient to point with one finger to the most painful area. |
Standing and Gait
| No | Test | Technique | Expected findings | Clinical tips and interpretation |
|---|---|---|---|---|
| 01 | Inspection, anterior | Patient stands with feet shoulder-width apart, facing you. Look from hip to foot (proximal to distal). | Normal: Neutral alignment, symmetrical quadriceps bulk. Abnormal: Genu varum or valgum, quadriceps (particularly the vastus medialis obliquus (VMO)) wasting, swelling, scars, bruising. | Alignment must be judged weight bearing. Supine assessment underestimates varus and valgus. |
| 02 | Inspection, lateral | Look from the side. | Normal: Full extension; physiological hyperextension varies between individuals. Abnormal: Excessive or asymmetric recurvatum, a flexed posture, prepatellar or infrapatellar bursal swelling, or a prominent tibial tubercle associated with Osgood–Schlatter disease. | Ask the patient to straighten the knee. If patient unable to extend the knee fully, just use the term knee in flexed position. Avoid calling it a fixed flexion deformity unless you have confirmed persistent loss of extension passively in the supine position. Recurvatum may reflect generalised hypermobility or ligament injury. |
| 03 | Inspection, posterior | Inspect both limbs from behind. | Normal: Symmetrical hamstring and calf bulk and neutral hindfoot alignment. Abnormal: Popliteal swelling, muscle wasting, hindfoot valgus or overpronation, or a “too many toes” sign. | If there is any popliteal swelling, do not commit to any diagnosis straightaway. Start by describing the mass (e.g. site, size, skin colour, border regularity), then only offer several differential diagnosis such as Baker cyst, lipoma, popliteal artery aneurysm. |
| 04 | Gait | Ask the patient to walk a few metres away and back. Stand in line with the patient: first observe the head, shoulders, trunk and pelvis, then observe lower limb alignment and movement as they return. | Normal: Symmetrical shoulder heights, normal stance, toe-off and swing, symmetrical step length. Abnormal: Antalgic gait (short stance on painful side), varus thrust (lateral thrust in stance, PLC or medial OA). | A varus thrust after injury, particularly in a young athlete, should prompt assessment of the PLC. It is not diagnostic on its own. |
| 05 | Squat (double leg) | If safe and appropriate, ask the patient to squat and stand up within a comfortable range. | Normal: Full pain-free squat. Abnormal: Pain at the joint line in deep flexion (may suggest meniscal tear), anterior knee pain (patellofemoral). | Do not request a deep squat in an acutely injured knee, suspected fracture, or when pain, instability or limited mobility makes it unsafe. Pain location alone does not establish a meniscal or patellofemoral diagnosis. |
| 06 | Lunges, forward | If safe and appropriate, ask the patient to perform a forward lunge with the unaffected limb leading, then repeat with the affected limb leading. | Observe pain, balance, knee alignment and control. Compare sides. | Use as a functional observation rather than a diagnostic test for a specific lesion. Avoid in acute injury or when weight bearing is unsafe. |
Sitting at the edge of the bed
| No | Test | Technique | Expected findings | Clinical tips and interpretation |
|---|---|---|---|---|
| 07 | Patellar tracking (J sign) | With the patient sitting and the legs hanging, ask them to actively extend the knee slowly from 90° to full extension while you observe the patella. | Normal: Smooth patellar tracking. Abnormal: An abrupt lateral movement near terminal extension, often within the last 20°, producing a J sign. | Patella is kept in the centre of the knee by the balance between soft tissues (quadriceps tendon, patellar tendon, medial and lateral patellar retinaculum) and bone congruity (patella and trochlear groove). Injury to any of this may lead to maltracking. During knee flexion, patella is stable as it sits within the trochlear groove. As the knee approaches full extension (from 20 to 0 degree), the patella exits the groove and is solely dependent on the soft tissue stabilisers. |
| 08 | Patellofemoral crepitus | Place your palm over the patella while the patient extends and flexes the knee actively. | Normal: Smooth movement. Abnormal: Palpable crepitus. | Crepitus alone is common and non-specific. Interpret in context, particularly when it is painful and reproduces the presenting symptoms. |
| 09 | Extensor mechanism | Assess active knee extension. In the supine position, also ask the patient to perform a straight leg raise. Apply resistance only if safe and appropriate. | Normal: Full active extension without lag. Abnormal: Inability to extend the knee or maintain extension may indicate extensor mechanism disruption, pain inhibition or weakness. | Palpate the quadriceps tendon, patella and patellar tendon for a defect. Avoid resisted testing if a fracture or rupture is suspected. |
Supine with the knee extended
| No | Test | Technique | Expected findings | Clinical tips and interpretation |
|---|---|---|---|---|
| 10 | Inspection in supine | Briefly (less than 10 seconds) inspect for scars, swelling or muscle wasting that may have been missed during standing inspection. | Fullness over the medial or lateral gutters, surgical scars or muscle atrophy. | Repeat inspection in the supine position may reveal subtle findings overlooked during standing inspection due to shadows or suboptimal lighting. Improved visibility in this position facilitates detection of these abnormalities. |
| 11 | Quadriceps bulk | Measure the circumference of the thigh. Use the same fixed landmark on both sides, e.g. 10 cm above the superior patellar pole or 15 cm above the medial joint line. | Compare measured circumference with the opposite side. Record the landmark, measurement and side-to-side difference. There is no single universal normal cutoff. | Circumference is affected by general physique and swelling, not only muscle bulk. |
| 12 | Temperature | Compare both knees with the back of your hand, moving from thigh to knee to shin. | Normal: Knee slightly cooler than thigh and similar to the other side. Abnormal: Warmth (inflammation, infection, acute haemarthrosis). | An acutely hot, swollen, painful knee warrants urgent assessment for septic arthritis. Fever may be absent and must not be required before considering infection. |
| 13 | Patellar tap | Milk / squeeze fluid from the suprapatellar pouch with one hand held above the patella, then press the patella backward with two fingers of the other hand. | Normal: No ballotable patella or distinct tap. Abnormal: A ballotable patella that contacts the femur suggests a moderate or large effusion. | Positive patellar tap means massive knee effusion. If negative, the fluid may be mild or absent. Thus, proceed to Fluid shift / Bulge test. |
| 14 | Fluid shift test / Sweep (bulge) test for small effusion | Empty the fluid from the medial gutter by sweeping / stroking the gutter two or three times. Then, sweep the lateral gutter and watch for rebulging of the medial gutter. | Normal: No fluid wave. Abnormal: A bulge reappears in the medial gutter. Detects small effusions. | This is not needed to confirm effusion if the patellar tap is already positive. |
| 15 | Patellar facet palpation | Push the patella medially and palpate the undersurface of the medial facet, then laterally for the lateral facet. Palpate superior and inferior poles. | Normal: Non-tender. Abnormal: Facet tenderness (patellofemoral pain, chondral lesion), inferior pole tenderness (patellar tendinopathy, Sinding-Larsen-Johansson in adolescents). | Palpate patellar tendinopathy at the inferior pole with the knee extended and quadriceps relaxed. |
| 16 | Patellar glide (mobility) | With the quadriceps relaxed, record the knee position used. Divide the patellar width into four quadrants. Gently translate the patella medially and laterally and estimate movement in quadrants; compare with the other knee. | Approximately 1–2 quadrants is a common clinical reference. Marked lateral translation, around 3 quadrants or more, may suggest hypermobility; less than 1 quadrant medially may suggest lateral soft tissue tightness. | Interpret with the knee position, endpoint, symptoms, apprehension and contralateral findings. The quadrant method is described by Kolowich et al.; these are clinical guides rather than universal diagnostic cutoffs. |
| 17 | Patellar grinding test | If used, support the knee posteriorly and apply gentle patellofemoral compression. | Retropatellar pain may be reproduced but is non-specific. | Do not diagnose chondral disease or patellofemoral pain from this test alone. Supporting the knee does not establish the diagnostic accuracy of the manoeuvre. |
| 18 | Clarke's sign | The traditional manoeuvre applies gentle pressure at the superior patellar pole while the patient contracts the quadriceps. | Pain or inability to maintain the contraction is traditionally considered positive, but healthy knees may also be uncomfortable. | Poor diagnostic value test for chondromalacia. |
| 19 | Patellar apprehension test | With the patient relaxed and the knee approximately 20–30° flexed, gently translate the patella laterally. Stop when apprehension occurs; do not attempt to dislocate the patella. | Normal: No apprehension. Abnormal: Apprehension, protective quadriceps contraction, or a request to stop suggests lateral patellar instability. | Moving variant (Ahmad et al.): translate the patella laterally through extension to 90° flexion and back, then repeat with medial translation. Apprehension with lateral translation and relief with medial translation supports instability. Use only when tolerated and with appropriate training. |
| 20 | Range of motion | For knee extension, lift both heels off the bed and compare. Alternatively, put hand beneath the knees and ask the patient to press down. For knee flexion, establish the baseline by asking patient to fully bend the unaffected knee and stay. Then, ask the patient to flex the affected knee actively, followed by passive movement if not symmetrical. | Extension lag: active extension falls short of the available passive range. Fixed flexion deformity: full extension cannot be achieved actively or passively. A true locked knee has a mechanical block to movement. | Extension lag can be caused by quadriceps weakness, swelling or post op / post injury pain. True locking causes include a meniscal tear (especially bucket handle tear), a loose body or an ACL stump. A truly locked knee requires urgent orthopaedic assessment. |
Supine with the knee flexed to 90 degrees
| No | Test | Technique | Expected findings | Clinical tips and interpretation |
|---|---|---|---|---|
| 21 | Posterior sag sign | At 90° knee flexion with the feet resting on the couch and the hips approximately 45° flexed, inspect from the side for posterior tibial sag. | Normal: The medial tibial plateau is approximately 1 cm anterior to the medial femoral condyle. Abnormal: Posterior sag, a less prominent tibial tuberosity or loss of the normal step-off suggests PCL insufficiency. | Check the medial step off before drawer testing. Pulling a posteriorly sagged tibia back to neutral may mimic an anterior drawer (false positive) and pushing it posteriorly without correcting the starting position may underestimate posterior drawer (false negative). |
| 22 | Quadriceps active test | With the hip approximately 45° flexed, knee at 90° and foot stabilised on the couch, ask the patient to gently attempt to slide the foot down the couch by contracting the quadriceps. Observe the tibial tuberosity from the side. | Normal: No appreciable anterior reduction. Abnormal: Anterior reduction of a posteriorly sagged tibia supports PCL insufficiency. The original study used a visible shift of at least 2 mm. | Supports PCL insufficiency; useful when posterior sag is subtle. |
| 23 | Palpation (anterior, medial, lateral) | Start away from the painful area. Anterior: tibial tuberosity, patellar tendon, patella, quadriceps tendon. Medial: medial joint line, medial femoral condyle, medial tibial plateau, MCL from femoral origin to insertion about 6 cm below the joint line, pes anserinus. Lateral: lateral joint line, lateral femoral condyle, lateral tibial plateau, LCL (palpable as a cord in the figure-4 position), fibular head, Gerdy's tubercle, ITB over lateral femoral epicondyle. | Normal: Non-tender structures. Abnormal: Joint line tenderness (meniscal tear, OA), MCL tenderness, pes anserine tenderness, LCL or fibular head tenderness. | Joint line tenderness is sensitive but not specific. Always combine with other meniscal tests. Use the figure-4 position to feel the LCL. |
| 24 | Anterior drawer test | With the hip approximately 45° flexed and knee at 90°, stabilise the foot gently. Grasp the proximal tibia with both hands, place the thumbs near the joint line, check that the hamstrings are relaxed, and draw the tibia forwards. | Normal: Minimal translation with a firm endpoint, equal to the other side. Abnormal: Increased anterior translation compared with the other side, soft or absent endpoint (ACL tear). | Pain, haemarthrosis and guarding can limit the test in acute injury. Check for posterior sag. Interpret with Lachman. |
| 25 | Posterior drawer test | Same position as the anterior drawer. Push the proximal tibia backward. | Normal: Firm endpoint and a normal medial tibial step-off. Abnormal: Increased posterior translation or loss of medial step-off. Grade I: <5 mm (plateau remains anterior), Grade II: 6–10 mm (plateau becomes flush), and Grade III: >10 mm (plateau lies posterior to the condyle) | A key test for PCL injury. Marked laxity should prompt assessment for combined ligament injury. |
Supine ligament and meniscal tests
| No | Test | Technique | Expected findings | Clinical tips and interpretation |
|---|---|---|---|---|
| 26 | Lachman test | With the patient supine and the knee flexed approximately 20–30°, stabilise the distal femur with one hand. Grasp the proximal tibia with the other, keeping the thumb near the anteromedial joint line, and translate the tibia forwards. Alternatively, place the examiner’s knee below the patient’s thigh. | Normal: Firm endpoint with minimal translation, equal to the other side. Abnormal: Increased anterior translation with a soft or absent endpoint (ACL tear). | More sensitive test for ACL injury. If hand size or thigh size limits the grip, cup the hand and pull the proximal tibia anteriorly instead of grasping it. |
| 27 | Valgus stress test (MCL) | At 30° flexion: support the thigh, hold the ankle, apply valgus force while palpating the medial joint line. Repeat at 0°. | Normal: Minimal opening with a firm endpoint. Abnormal: Increased opening at 30° suggests MCL injury. Opening in full extension suggests potential cruciate injury. | Grade I: pain without increased laxity, Grade II: increased laxity with a firm endpoint, Grade III, gross laxity with a soft or absent endpoint. |
| 28 | Varus stress test (LCL) | As for valgus stress but apply a varus force, palpating the lateral joint line. Test at 30° and 0°. | Normal: Firm endpoint without increased lateral opening. Abnormal: Increased opening at 30° suggests LCL injury. Opening in full extension suggests potential cruciate ligament or posterolateral corner injury. | Isolated LCL injury is uncommon. Assess the PLC too. |
| 29 | McMurray test | Patient supine, knee maximally flexed. One hand holds the foot, the other palpates the joint line. Rotate the tibia externally and extend the knee slowly. Then reset to maximum knee flexion, rotate internally and extend. | Normal: Smooth movement, no click or pain. Abnormal: Original sign: a palpable or audible click (thud) over the joint line as the torn posterior horn is caught. Modern use also counts reproduction of joint line pain. | The original description emphasised rotation and a palpable click. Later, modifications added valgus force during external tibial rotation and varus force during internal tibial rotation. No need to remember which rotation is for which meniscus. When the pain is produced, just ask the patient to pin point the location. |
| 30 | Pivot shift test | Patient supine and relaxed. Hold the foot in internal rotation with the knee extended. Apply valgus force at the knee (with axial load) and slowly flex. In ACL deficiency, the lateral tibial plateau starts subluxed anteriorly and reduces with a clunk at about 20 to 40° as the ITB passes behind the axis of rotation. | Normal: No shift. Abnormal: Visible or palpable reduction clunk. Graded I (glide), II (clunk), III (gross, transient locking). | A positive pivot shift supports ACL-related rotatory instability, but guarding commonly produces a negative result in an awake patient. It should be performed gently by a trained examiner. A study showed poor outcome of conservative management in patients with positive Pivot shift test. |
Prone examination
| No | Test | Technique | Expected findings | Clinical tips and interpretation |
|---|---|---|---|---|
| 31 | Dial test (tibial external rotation test) | With the patient prone and the knees flexed to 30°, stabilise the thighs to limit hip rotation. Apply gentle, comparable external rotation to both feet and compare the thigh–foot angles. Repeat at 90°. | An increase of more than approximately 10° compared with the opposite side raises concern for rotational instability. A positive test at 30° suggests PLC injury; persistence or increase at 90° raises concern for associated PCL injury. | These patterns are suggestive, not definitive. Interpret with varus stress, PCL tests and the rest of the examination. An assistant can help stabilise the thighs; avoid forcing maximal rotation. |
| 32 | Apley grinding test | With the patient prone and the knee at 90°, stabilise the thigh. Apply gentle axial compression through the heel while internally and externally rotating the tibia. | Joint-line pain with compression and rotation may support meniscal pathology but is non-specific. | Use alongside other findings; a negative result does not exclude a meniscal tear. Avoid forceful compression. |
| 33 | Posterior palpation | Palpate the popliteal fossa, hamstring tendons (biceps femoris laterally, semitendinosus and semimembranosus medially), and gastrocnemius heads. | Normal: No mass or tenderness. Abnormal: Baker's cyst (medial, between semimembranosus and medial gastrocnemius), popliteal artery aneurysm (pulsatile), hamstring tendinopathy. | Do not repeatedly compress or manipulate an unexplained pulsatile mass. Arrange appropriate vascular assessment when a popliteal aneurysm is suspected. |
Standing functional assessment
| No | Test | Technique | Expected findings | Clinical tips and interpretation |
|---|---|---|---|---|
| 34 | Thessaly test | Patient stands on one leg while the examiner holds both hands for support. With the knee flexed to 5°, the patient rotates the knee and body internally and externally three times. Repeat with the knee at 20°. Test the normal leg first. | Normal: No discomfort. Abnormal: Joint line pain or a sense of locking or catching (meniscal tear). | The original study reported high accuracy at 20°; subsequent research found lower performance. Use as one part of assessment, not a stand-alone rule-in or rule-out test. Avoid in acute painful injury, instability or unsafe single-leg weight bearing. |
| 35 | Single-leg balance | With a stable support nearby and close supervision, ask the patient to stand on one leg for up to 30 seconds with hands on hips and eyes open. Repeat on the other side. Consider eyes closed only if safe. | Observe sway, touch-downs, compensatory hip or trunk movement and side-to-side differences. | Performance reflects balance, strength, pain and other sensory inputs; it is not a specific diagnostic test of knee proprioception. Useful as a rehabilitation baseline. |
| 36 | Functional tests (if appropriate) | When appropriate for rehabilitation, assess a single-leg squat, single hop for distance and triple hop. Record symptoms, movement quality and performance on both sides. | For hop distance, limb symmetry index = affected-side distance ÷ unaffected-side distance × 100. A threshold of at least 90% is commonly used within a test battery; it is not a universal definition of normal function. | These tests belong to rehabilitation and return-to-sport assessment, not the acute diagnostic examination. Consider strength, symptoms, movement quality, psychological readiness and sport demands. Symmetry can conceal bilateral weakness and does not establish readiness by itself. |
Completing the examination
- Examine the hip and ankle (joint above & below)
- Perform a lower limb neurovascular examination.
- Consider generalised hypermobility using the Beighton score when indicated.
- Thank the patient.
Abbreviations
| Abbreviation | Meaning |
|---|---|
| ACL | Anterior cruciate ligament |
| PCL | Posterior cruciate ligament |
| MCL | Medial collateral ligament |
| LCL | Lateral collateral ligament |
| PLC | Posterolateral corner |
| ITB | Iliotibial band |
| OA | Osteoarthritis |
| VMO | Vastus medialis obliquus |
| MPFL | Medial patellofemoral ligament |
Disclaimer
This physical examination note does not represent any department of any university.