Examination of the knee


  • From the end of the couch and with the patient’s legs straight, observe the knees, comparing one with the other, for symmetry and alignment.
  • Is the posture of the knee normal? Look for valgus deformity – where the leg below the knee is deviated laterally (knock-kneed) – and for varus deformity – where the leg below the knee is deviated medially (bow-legged).
  • Check for a knee flexion deformity (distinguishing this from hip flexion deformity by examining hip movements as above).
  • Check for muscle wasting or scars.
  • Look for redness suggesting inflammation or infection
  • Look for obvious swelling.
  • Check for a rash suggesting psoriasis.

NOTE: Popliteal swellings, varus and valgus deformities may be more apparent with the patient weight-bearing.


  • Using the back of your hand, feel the skin temperature, starting with the mid-thigh and comparing it to the temperature over the knee. Compare one knee to the other.
  • Palpate for tenderness along the borders of the patella.
  • With the knee flexed to 90º, palpate for tenderness and swelling along the joint line from the femoral condyles to the inferior pole of the patella, then down the inferior patella tendon to the tibial tuberosity.
  • Feel behind the knee for a popliteal (Baker’s) cyst.
  • Assess for an effusion by performing a patellar tap, as described for the screening examination.
  • If there is no obvious patellar tap, assess for a fluid bulge by cross fluctuation. Stroke the medial side of the knee upwards (towards the suprapatellar pouch) to empty the medial compartment of fluid, then stroke the lateral side downwards (distally) (see Figure 15). The medial side may refill, and produce a bulge of fluid indicating an effusion.

Figure 15

Cross fluctuation (the bulge sign)


  • Ask the patient to flex the knee as far as possible to assess active movement. Making sure the patient is fully relaxed, assess passive movement. This is done by placing one hand on the knee (feeling for crepitus) and flexing the knee as far as possible, noting the range of movement. Assess full flexion and extension of the knees, comparing one to the other.
  • With the knee flexed to 90º, check the stability of the knee ligaments. Look initially from the side of the knee, checking for a posterior sag or stepback of the tibia, suggesting posterior cruciate ligament damage.
  • Perform an anterior draw test. Place both hands round the upper tibia, with your thumbs over the tibial tuberosity and index fingers tucked under the hamstrings to make sure these are relaxed. Stabilize the lower tibia with your forearm and gently pull the upper tibia forward (see Figure 16). In a relaxed, normal patient there is normally a small degree of movement. More significant movement suggests anterior cruciate ligament laxity.
  • Assess medial and lateral collateral ligament stability by flexing the knee to 15º and alternately stressing the joint line on each side. Place one hand on the opposite side of the joint line to that which you are testing, and apply force to the lower tibia (see Figure 17). This may be done with the leg on the couch or with the lower tibia supported on the examiner’s pelvis.

Figure 16

Figure 17

Assessing medial and lateral collateral ligament stability.


  • Ask the patient to stand and then walk a few steps, looking again for a varus or valgus deformity (see below).

Examination of the knee: checklist

  • Introduce yourself/gain consent to examine

With the patient lying on couch:

  • Look from the end of the couch for varus/valgus deformity, muscle wasting, scars and swellings
  • Look from the side for fixed flexion deformity
  • Assess skin temperature
  • With the knee slightly flexed palpate the joint line and the borders of the patella
  • Feel the popliteal fossa
  • Perform a patellar tap and cross fluctuation (bulge sign)
  • Assess fulll flexion and extension (actively and passively)
  • Assess stability of knee ligaments – medial and lateral collateral – and perform anterior draw test

With the patient standing:

  • Look again for varus/valgus deformity and popliteal swellings
  • Assess the patient's gait


CMC(J) carpometacarpal (joint); CT computerized tomography; DEXA dual-energy x-ray absorptiometry; DIP(J) distal interphalangeal (joint); ESR erythrocyte sedimentation rate; GALS gait, arms, legs and spine; MCP(J) metacarpophalangeal (joint); MRI magnetic resonance imaging; MTP(J) metatarsophalangeal (joint); NSAID non-steroidal anti-inflammatory drug; OA osteoarthritis; PIP(J) proximal interphalangeal (joint); RA rheumatoid arthritis; REMS regional examination of the musculoskeletal system.