Inflammatory Pain

For Medical Students

What It Tests

Asking about the inflammatory pattern tests whether the knee is inflamed rather than mechanically worn, and the two are managed by different specialties.

The pattern has four features: stiffness after rest that eases with movement, prolonged morning stiffness, involvement of other joints, and systemic symptoms.

A mechanical knee is the opposite on each: better with rest, worse with use, one joint, no systemic features.

How It Is Performed

Ask how long the knee is stiff in the morning before it loosens, pressing for minutes.

Ask whether it is worse after sitting still and better after moving about, which is the core inflammatory pattern.

Ask about other joints, including the hands, feet and spine, and about swelling in them rather than only pain.

Ask about systemic features: fatigue, fever, weight loss, rashes, eye problems, bowel symptoms and psoriasis.

Ask about family history, since several of the relevant conditions cluster.

What a Positive Means

Prolonged morning stiffness with polyarticular involvement and systemic features points to an inflammatory arthropathy and needs a rheumatological assessment rather than a mechanical one.

An acutely hot, swollen, exquisitely painful knee in a single joint is a crystal arthropathy or an infection and is urgent. 4.8.10 covers crystal arthropathy.

Episodic swelling with normal periods between episodes, in a single knee, can be either mechanical or inflammatory and the other features decide. 4.8.8 covers chronic effusions.

Short morning stiffness easing within half an hour, in a single knee, with activity-related pain, fits degenerative disease. 4.18.1 covers early disease.

MRCS Level

What a Positive Means

The reasoning expected is that an inflammatory pattern changes the whole pathway rather than adding a diagnosis.

A synovitic knee will have an effusion, warmth and a boggy feel on palpation, which the examination will confirm. 4.8.9 covers synovitis.

Arthroscopy of an inflamed knee for mechanical symptoms frequently disappoints, because the symptom is synovitis and the findings are incidental.

An inflammatory arthropathy with secondary degenerative change can present exactly like primary degenerative disease, and the history is usually the only thing that separates them in clinic.

A monoarthritis in a sexually active young adult, or in anyone immunosuppressed, has a differential that does not belong in this chapter and needs excluding first.

How Good It Is

The inflammatory pattern is one of the better discriminators in the knee history, because its features are concrete and its opposite is equally concrete.

The timing features are the most reliable: stiffness after rest, and morning stiffness duration.

Polyarticular involvement is reliable when present and unreliable when absent, since several inflammatory conditions begin in one joint.

Systemic features are specific and insensitive: their presence matters a great deal and their absence excludes little.

FRCS Level

How Good It Is

At decision level the inflammatory pattern is a contraindication question as much as a diagnostic one.

An operation on a knee with active synovitis of inflammatory origin has a different risk profile and a different expected result, and the history is where that is identified.

Arthroplasty in inflammatory arthropathy is a recognised and different proposition from arthroplasty in degenerative disease, including in the medication that has to be managed around it.

A patient on immunosuppression or biological therapy has an infection risk that changes the consent conversation and the perioperative plan, and the question that identifies them is a history question about other joints and about medication.

Where It Misleads

The commonest error is not asking about other joints, which converts a systemic problem into a knee problem.

The second is accepting morning stiffness without a duration, which loses the discrimination entirely.

The third is a knee with both: a patient with an inflammatory arthropathy can also tear a meniscus, and attributing everything to the arthropathy is the mirror of attributing everything to the tear.

And a knee that became inflamed after an injection or an operation is an infection question first, whatever the background diagnosis. 4.2.31 covers injections.

Fellowship Level

Where It Misleads

In referred practice the inflammatory pattern is most often missed in the patient who has already had mechanical surgery.

A knee that was arthroscoped, improved briefly and returned to a stiff, swollen, morning-worse state was probably inflamed before the operation, and the pattern was there to be found.

A knee that developed the pattern after an operation raises low grade infection, a reactive synovitis, or a metal or cement reaction, and the sequence of onset separates them. 4.20.9 covers revision assessment.

In a multiply operated knee, persistent synovitis is a recognised and frequently unexplained end state, and recognising it is more useful than continuing to look for a mechanical cause.

The honest limit is that distinguishing a reactive from an infective synovitis cannot be done from the history, and this page is about identifying who needs that distinction made rather than making it.

No figure here supports any of these claims, under decision 023.