Knee Osteoarthritis

Who: Adults 45+, though it starts earlier after a knee injury. More common in women.
What: Activity-related knee pain, with morning stiffness that lasts 30 minutes or less.
How it behaves: Load-related and mechanical. Worse on stairs, prolonged standing and after a big day. Eases with rest, stiffens up again after sitting.

The illness script in one line: activity-related knee pain in an adult 45 or over, with short-lived morning stiffness — a diagnosis you make from the history and the examination, and do not image to confirm.

The numbers that matter:

(Burden: GBD 2021 [1]. Attributable fractions: [2], 46 cohort studies.)

✅ Australia has a current national standard for this pattern. Anchored to the Osteoarthritis of the Knee Clinical Care Standard (ACSQHC, revised 2024) — eight quality statements, national indicators, and the reference point an Australian educator will assume you know. Secondary: the RACGP knee and hip OA guideline (2018) — cite it, but note the RACGP's own site says it is being updated.

This is only the second pattern in CliniStudy with a real Australian anchor. Use it.

Pattern > Label. The label is not in doubt. What you're actually deciding is: is this behaving like OA, is anything else going on, and what do I put this person's energy into.

Five stages, in the order your course teaches them. Insidious, so run BEHAVIOUR before HISTORY.

MAIN PROBLEM

Get the activity, not the ache. Stairs. Getting out of the car. Standing at work. Walking the dog. Kneeling in the garden. That's your outcome measure, and it's what you'll re-test.

BODY CHART

• Usually medial or anteromedial, often pointed to with a whole hand or a circling motion — not one finger.
• Ask about the hip and the back. Referred pain from the hip is on the ACSQHC atypical-features list, and groin pain with restricted hip internal rotation is a different pattern.
• Bilateral is common and normal here. So is a worse side.

BEHAVIOUR

• Aggs: stairs (down usually worse than up), squatting, kneeling, prolonged standing, getting up after sitting, a longer walk than usual.
• Eases: rest, sitting, movement after the first few steps, heat.
• Severity: VAS 0–10 at best / at worst / right now.
• 24-hr pattern: stiff first thing, loosens within 30 minutes, stiffens again after sitting ("gelling"), sore by the end of a big day.
• Morning stiffness is a diagnostic item here, and the threshold matters. ≤ 30 min supports OA. > 30 min is one of the atypical features that should make you think inflammatory arthropathy (ACSQHC 2024, quality statement 1).
• Night: aching after a heavy day, eased by position. Unremitting night pain is not this.
• Irritability: vigour, severity, time to settle. It sets your starting exercise dose.

HISTORY

• Gradual, over months to years, with flares. Ask what a flare looks like and what triggers it — flares are usually a load error, not a deterioration.

• The risk-factor questions that actually earn their place (Silverwood 2015, 46 cohorts, adults 50+):

  Question	Odds ratio for knee OA
  Previous knee injury	2.83 (95% CI 1.91–4.19)
  Obesity	2.66 (2.15–3.28)
  Overweight	1.98 (1.57–2.20)
  Female	1.68 (1.37–2.07)
  Smoking	0.92 (0.83–1.01) — not significant, so stop asking as though it is

• What have they been told, and have they had a scan? If they've seen an X-ray report, that's now part of the problem you're treating — see §5.

SPECIAL / SCREENING QUESTIONS

General health, weight change, fever, malignancy history, inflammatory features, medications, and any recent knee trauma. See §4.

The diagnostic triad hiding in your subjective

EULAR's evidence review found three symptoms and three signs carry the diagnosis. The three symptoms are all yours, in the subjective: persistent knee pain, limited morning stiffness, reduced function [3]. Get those three and you're halfway to a confident diagnosis before you've touched the knee.

Top competing patterns, one discriminating feature each. Rank them, then rule out the dangerous one first.

The meniscus row, rewritten — and why

A common teaching offers locking or clicking, joint-line tenderness and a positive McMurray or Thessaly as the thing that separates a meniscal tear from OA. In an adult over 50, that is a false discriminator, and this is worth knowing properly.

In the Framingham MRI study of 991 people aged 50–90 [4]:

• Meniscal tear prevalence ran from 19% (95% CI 15–24) in women aged 50–59 to 56% (46–66) in men aged 70–90.
• Among knees with radiographic OA, a tear was present in 63% of people with symptoms and 60% of people without.
• 61% of everyone with a meniscal tear had no knee pain, aching or stiffness in the previous month.

So finding a tear tells you almost nothing about why this knee hurts. The Australian standard says it in one line: meniscal changes, such as tears identified by imaging, do not warrant arthroscopy.

What still matters is TRUE mechanical locking — a physical block to full extension that the patient cannot release themselves. Not "it clicks". Not "it catches". Not "it feels like it might give way". That one finding is a genuinely different pathway, and it's one of the only exceptions the standard allows for arthroscopy.

Jones' hypothesis categories that change your plan here: patient perspectives (what they believe the joint is doing — this is the big one), contributing factors (load, weight, work, sleep), and precautions (irritability today).

If it's stiff for two hours and it's in three joints, stop calling it osteoarthritis.