Patient handout

Knee pain evaluation (Ottawa knee → OA / internal derangement / crystal / septic)

PRODUCTION

1. Your condition

This handout is for knee pain evaluation (ottawa knee → oa / internal derangement / crystal / septic). Your care team identified this based on: acute knee injury (twist / fall / direct blow) — trauma triage gate (ottawa knee rule, stiell ann emerg med 1995 / jama 1996; kazemi meta-analysis pmid 37215241).

Other reasons your team may use this plan: mechanical locking / catching / giving-way — internal derangement (meniscus / acl / loose body) (aaos meniscal cpg 2024 pmid 40674138); acute hot, swollen, painful knee ± fever — septic vs crystal monoarthritis (margaretten jama 2007 pmid 17405973); insidious anterior/peripatellar pain worse with stairs/squatting/prolonged sitting — patellofemoral pain (jospt 2019 pmid 31475628).

2. Your medications

Take these medications exactly as prescribed. Do not stop or change a dose without talking to your provider.

Medication	Starting dose	How	When	What it does
emergent arthrocentesis + empiric IV antibiotics + orthopaedic washout (septic arthritis)	—	—	—	Septic arthritis is limb/life-threatening; synovial WBC >50K LR 7.7, >100K LR 28 (Margaretten JAMA 2007 PMID 17405973). Empiric anti-staph cover after cultures; do NOT delay for imaging
knee radiograph per Ottawa Knee Rule	—	—	—	Pooled sens ~98% (95% CI 96–99), LR− ~0.12 → safely omit films if all 5 negative, ~49% reduction (Kazemi PMID 37215241; Emparanza PMID 11574791)
vascular assessment (pulses + ABI ± CT angiography) for knee dislocation/multiligament	—	—	—	Popliteal artery injury accompanies up to ~⅓ of knee dislocations — limb-threatening; serial exam + ABI, CTA if ABI <0.9 (vascular surgery)

Plan: Knee pain — phenotype routing + symptomatic analgesia (comorbidity-gated) (Stiell JAMA 1996; AAOS CPGs; JOSPT 2019 PMID 31475628; Frobell NEJM 2010 PMID 20660401)

3. Your action plan

Use these zones to know what to do based on how you feel.

GREEN — Stable — improving with the agreed plan

If you have:

Pain manageable with simple analgesia / topical gel
Doing the prescribed exercise/rehab program
No locking, giving-way, fever, or new swelling

Do this:

Keep doing your rehabilitation exercises — for kneecap pain and many ACL/meniscus injuries this is the main treatment (JOSPT 2019; Frobell NEJM 2010)
Use topical anti-inflammatory gel or paracetamol rather than anti-inflammatory tablets when possible, especially if you have kidney/heart/stomach problems
Build activity back gradually as comfort allows
Keep your follow-up appointment to confirm the diagnosis and recheck progress

YELLOW — Flare or not improving

If you have:

Pain or swelling worsening or not improving after a few weeks of the plan
Knee feels unstable or gives way occasionally
Difficulty with stairs / squatting increasing

Do this:

Relative rest and ice; continue gentle range-of-motion within comfort
Optimise simple analgesia; only add an anti-inflammatory tablet at the lowest dose if your kidney/heart/stomach history allows (ask first)
Contact your clinician to review the plan and consider imaging or specialist referral
If a sports/ACL injury, ask whether the rehab vs surgery plan should be revisited

Call your provider if:

No improvement within ~6 weeks of the agreed plan
Repeated giving-way or the knee locking briefly
Side effects from medication (stomach pain, ankle swelling, BP rise)

RED — Possible emergency — seek urgent care now

If you have:

Hot, very swollen, painful knee with fever (possible joint infection)
Cannot straighten or lift the leg / locked knee that will not move (tendon rupture or trapped cartilage)
Knee that came out of joint, a cold/pale/numb lower leg, or severe calf tightness after injury
Cannot bear any weight after an injury

Do this:

A hot swollen knee with fever — go to the emergency department now (this needs joint fluid testing to exclude infection — Margaretten JAMA 2007)
Unable to straighten/lift the leg or a locked knee — urgent assessment for tendon rupture or a trapped meniscus
Dislocated knee or cold/numb/pale lower leg — call emergency services immediately (possible artery injury)

Call your provider if:

Always seek emergency care for fever + a hot swollen joint, a dislocated knee, or a cold/numb leg

4. When to seek emergency care

Call 911 or go to the nearest emergency room right away if you have:

Acute hot swollen knee + fever / immunocompromise / prosthetic joint / synovial WBC high — septic arthritis until arthrocentesis excludes it; route to id.osteomyelitis-septic-arthritis.v1 above the treatment threshold (Margaretten JAMA 2007 PMID 17405973; Carpenter Acad Emerg Med 2011 PMID 21843213)(life-threatening)
Knee dislocation / multiligament injury / absent or asymmetric distal pulses / ABI <0.9 — popliteal artery injury (limb-threatening)(life-threatening)
Cannot actively extend the knee / perform straight-leg-raise + palpable gap (quadriceps or patellar tendon rupture) — a cannot-miss not captured by the Ottawa imaging gate alone
Fixed mechanical block to terminal extension (true locked knee) — displaced bucket-handle meniscal tear or loose body (AAOS meniscal CPG 2024 PMID 40674138)

5. Follow-up

Phenotype-specific: ACL — re-evaluate need for delayed reconstruction by activity/instability; counsel on post-traumatic OA risk (~50% at 10–20 yr after ACL/meniscus injury — Lohmander Am J Sports Med 2007 PMID 17761605) regardless of surgical choice. Meniscus — recovery expectations, OA-risk counselling, preserve meniscal tissue if operated (AAOS CPG 2024 PMID 40674138). PFP — long-term exercise maintenance (relapsing course — JOSPT 2019 PMID 31475628). OA — route msk.osteoarthritis.core.v1 chronic pathway. Return precautions: fever + hot joint, locking, recurrent giving-way, inability to extend

6. Sources

Guideline: Ottawa Knee Rule (Stiell et al, Ann Emerg Med 1995 / JAMA 1996; pooled meta-analysis Kazemi Arch Acad Emerg Med 2023) + AAOS Acute Isolated Meniscal Pathology CPG 2024 + AAOS ACL CPG 2022 + JOSPT 2019 Patellofemoral Pain CPG + Margaretten JAMA Rational Clinical Examination (septic arthritis) 2007 + Carpenter Acad Emerg Med 2011 evidence-based diagnostics (septic-arthritis interval LRs, conditional host-dependence, T_test/T_treat thresholds)