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Temperature Assessment

Page 4.6.2 · Palpation · examination page

Five seconds with the back of the hand, and the finding that decides whether the rest of the examination should happen.

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The same topic at 4 depths

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Temperature Assessment

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For Medical Students

What It Tests

Temperature assessment compares the warmth of the two knees and of the limb above and below each, and it tests for inflammation and for circulation.

A warm knee is an inflamed knee, and inflammation includes infection, crystal arthropathy, inflammatory arthritis and the response to a recent injury. 4.8.9 covers synovitis.

A cold foot is a circulation finding, and in a knee with multiple ligament injuries it is the most urgent observation in the whole examination. 4.11.7 covers that sequence.

How It Is Performed

Use the back of the hand, which is more sensitive to temperature than the palm.

Compare the two knees directly, moving between them rather than assessing one and then the other.

Compare each knee with the thigh and the calf of the same limb, since a warm knee against a warm limb is different from a warm knee against a cool one.

Feel both feet and compare them, and feel the pulses if either is cool. 4.11.7 covers the vascular examination.

Do this before anything that hurts, because it needs a relaxed and cooperative patient and provides information immediately.

What a Positive Means

A knee warmer than its fellow indicates inflammation, and the differential runs from a recent injury to a septic joint. 4.3.6 covers skin changes.

Warmth with redness, swelling and an inability to move the knee is a septic joint until proven otherwise, and the examination stops there.

Warmth with a chronic effusion and no injury raises inflammatory arthritis or crystal disease. 4.8.10 covers crystal arthropathy.

Warmth over a localised area rather than the whole joint suggests a superficial process such as a bursitis rather than an intra-articular one.

A cool foot with absent or reduced pulses in an injured knee is an arterial injury until excluded, and that conclusion is reached here. 4.11.7 covers it.

Key Learning Points

  • Use the back of the hand and compare the two knees directly.
  • A warm knee is an inflamed knee, and the differential includes a septic joint.
  • Compare each knee with the limb above and below it.
  • Localised warmth suggests a superficial process rather than an intra-articular one.
  • A cool foot with reduced pulses in an injured knee is an arterial injury until excluded.

MRCS Level

How It Is Performed

In a viva temperature is the first touch and saying so demonstrates a system rather than a habit.

The expected points are the back of the hand, the direct comparison, the limb above and below, both feet, and the pulses where indicated.

Say that you would do this before the painful parts of the examination, and say why.

Say what warmth would stop you doing, because the useful answer includes not examining a knee you suspect of being septic.

Say that you would take the temperature of the patient as well as of the knee, since a systemically unwell patient with a warm knee is a different problem. 4.8.9 covers synovitis.

What a Positive Means

The reasoning expected is that the knee is superficial, so an increase in intra-articular blood flow raises the skin temperature measurably by hand, which is not true of deeper joints.

Inflammation increases synovial blood flow and produces both the warmth and the effusion, which is why the two findings travel together. 4.8.1 covers normal fluid physiology.

The comparison with the limb distinguishes a local process from a generally warm patient, which is the commonest confounder.

Arterial injury reduces distal perfusion, and the foot is where that is felt rather than the knee, which is why the examination extends beyond the joint. 2.10.6 covers the nerve that travels with that risk.

How Good It Is

Temperature by hand is a reliable screen for a substantial difference and insensitive to a small one.

It is non specific. Every cause of inflammation produces it, so it prompts a differential rather than resolving one.

It is more reliable than skin colour in patients with darker skin, where erythema is harder to read, which makes it the more useful of the two findings in that setting. 4.3.6 covers skin changes.

Its most consequential use is the cool foot, where the finding is urgent and the assessment takes seconds. 4.11.7 covers it.

No figures appear for any accuracy comparison on this page, under decision 023, and the comparison is the claim being made.

Key Learning Points

  • The knee is superficial, so increased intra-articular blood flow raises skin temperature detectably.
  • Inflammation produces both the warmth and the effusion, so the two travel together.
  • Comparing with the limb distinguishes a local process from a generally warm patient.
  • It is more reliable than skin colour in patients with darker skin.
  • Its most consequential use is the cool foot.

FRCS Level

How Good It Is

At decision level temperature changes the pathway rather than the operation, and changing the pathway is occasionally the most important thing an examination does.

A warm knee with an effusion in a patient with a prosthesis or a graft raises infection, and that has to be excluded before any elective plan proceeds. 4.3.6 covers the skin.

A persistently warm knee with recurrent effusions and no mechanical findings is an inflammatory or crystal problem, and operating on it achieves nothing. 4.8.8 covers chronic effusions.

A cool foot in a multiligament knee changes the order of everything and is the one finding in Section 4 with a time limit measured in hours. 4.11.7 covers it.

In the elective knee a slightly warm joint after recent surgery is expected, and distinguishing expected from excessive is a judgement that needs the time since surgery. 4.7.10 covers post-operative range.

Where It Misleads

The commonest error is not doing it, since it takes seconds and is easy to skip.

The second is using the palm, which is less sensitive.

The third is assessing one knee and then the other rather than moving between them.

The fourth is attributing warmth to a recent injury without considering infection, which is the error with the worst consequences.

The fifth is omitting the feet, which is where the urgent finding is. 4.11.7 covers it.

Key Learning Points

  • Temperature changes the pathway rather than the operation.
  • A warm effused knee with a prosthesis or a graft raises infection before any elective plan.
  • A persistently warm knee with no mechanical findings is not a surgical problem.
  • A cool foot is the one finding in Section 4 with a time limit in hours.
  • Attributing warmth to a recent injury without considering infection is the worst error here.

Fellowship Level

Where It Misleads

In referred practice temperature is most useful in the knee that has been operated on and is not settling.

A knee that remains warm months after a reconstruction or an arthroplasty raises low grade infection, and a normal inflammatory marker does not exclude it in this setting. 4.3.6 covers the skin.

A knee that is warm with a recurrent effusion and a normal mechanical examination has an inflammatory process, and repeated arthroscopy for it is a recognised pattern of futile treatment. 4.8.9 covers synovitis.

A chronically warm knee in a patient on immunosuppression deserves a lower threshold for investigation, since the usual signs are blunted.

In a knee with previous vascular injury or repair the baseline perfusion may be abnormal, so a cool foot has to be compared with the recorded baseline rather than with the other side. 4.11.7 covers that assessment.

In medicolegal work a recorded knee temperature is almost never available, and the absence of a documented vascular examination in a multiligament injury is one of the most serious gaps a record can have. 4.23.7 covers that setting.

Key Learning Points

  • A knee still warm months after surgery raises low grade infection.
  • A normal inflammatory marker does not exclude it in that setting.
  • A warm knee with a recurrent effusion and normal mechanics is not helped by arthroscopy.
  • Immunosuppression blunts the usual signs and lowers the threshold for investigation.
  • The absence of a documented vascular examination in a multiligament injury is a serious gap.

Explore Further

Where this topic came from and where it goes next in the spiral.

References

No reference list is attached to this draft. Evidence verification has not run, because source retrieval was unavailable at generation time. Under the Operations Handbook a missing reference is acceptable and an invented one is a critical failure, so nothing has been cited and no citation marker appears in the text. This page carries no diagnostic accuracy figure, which is decision 023 rather than an omission. The comparative standing of these tests is standard teaching and a specific sensitivity written from memory is the same class of claim as an invented citation, so ACC-001 refuses the number and the page states the comparison. A reviewer with the literature can add the figures into How Good It Is without restructuring the page, and chapter 3.17 lists the studies the figures would come from. Any measurement here, including a flexion angle, is written from standard teaching, has not been checked, and is registered under decision 006 in pipeline/config/figures with a verification state of UNVERIFIED_FROM_MEMORY.

Safety. KneeSchool is educational and does not give individual medical advice. Seek urgent assessment for a knee that cannot bear weight after an injury, a hot swollen knee with a fever, or new numbness, weakness or coldness in the leg or foot.