Knee Pain
Knee pain is a common musculoskeletal complaint arising from injury, overuse, or degenerative, inflammatory, or infectious processes affecting the bones, cartilage, ligaments, tendons, or bursae of the knee joint.
Murtagh Diagnostic Strategy
| Category | Diagnosis | Key Discriminator | Cantonese Question / Finding | Probability |
|---|---|---|---|---|
| Probability Diagnosis | Knee osteoarthritis [1][2] | Age > 50, gradual onset, use-related pain, < 30 min morning stiffness, crepitus, bony enlargement | 「行路、落樓梯痛唔痛？朝早僵硬幾耐？」(Usage pain, short morning stiffness) | ~35% |
| Patellofemoral pain syndrome | Anterior knee pain, worse stairs/prolonged sitting, young active patient | 「行樓梯或者坐耐咗企起身痛唔痛？」Patellar grind test +ve | ~15% | |
| Meniscal tear (degenerative) [3][4] | Twisting injury or degenerative; locking/catching, joint-line tenderness | 「有冇試過扭到？隻膝頭有冇鎖住過？」McMurray test +ve | ~10% | |
| Serious Not To Miss | Fracture (tibial plateau, patella) | Acute trauma, unable to weight-bear, haemarthrosis | 「受傷之後行唔行到路？」Bony tenderness, deformity | ~3% |
| DVT / Baker's cyst rupture | Posterior knee/calf swelling + pain; unilateral calf swelling [6] | 「小腿有冇腫？」Calf tenderness, asymmetric swelling | ~2% | |
| Septic arthritis [5] | Acute hot swollen joint, fever, unable to bear weight; EMERGENCY | 「隻膝頭有冇又紅又腫又熱？有冇發燒？」Warm, erythematous, tense effusion | ~1% | |
| Malignancy (bone tumour / metastasis) | Night pain, weight loss, age < 20 or > 50, progressive unrelenting pain | 「夜晚會唔會痛醒？有冇瘦咗？」Bony mass, restricted ROM | <1% | |
| Pitfalls | Gout / pseudogout [5] | Acute monoarthritis, very red/hot/swollen, history of gout or chondrocalcinosis | 「以前有冇痛風？」Urate crystals on aspirate | ~5% |
| Ligament injury (ACL/MCL) [3] | Acute trauma + pop + instability + immediate swelling | 「受傷嗰陣有冇聽到「啪」一聲？」Lachman test / valgus stress test +ve | ~5% | |
| Referred pain from hip OA | Anterior knee/thigh pain with normal knee exam; limited hip ROM | 「髀骹有冇痛？」(Hip pain?) Internal rotation of hip restricted | ~3% | |
| Osgood-Schlatter disease [7] | Adolescent, anterior knee pain, tender tibial tuberosity, after sport | 「你幾多歲？做運動之後膝頭骨下面痛唔痛？」Tender tibial tuberosity swelling | ~2% | |
| Masquerades | Depression | Chronic pain + low mood + sleep disturbance + loss of function | 「心情點呀？有冇覺得好灰？」 | ~10% |
| Spinal pathology (L3/4 radiculopathy) | Knee pain with back pain, dermatomal sensory change, reduced knee jerk | 「腰有冇痛？腳有冇痺？」Diminished knee reflex | ~3% | |
| Peripheral vascular disease | Claudication pain in calf/knee area on exertion, absent pulses [8] | 「行路行遠啲小腿痛唔痛？要停低休息？」Absent dorsalis pedis pulse | ~2% | |
| Trying to Tell Me Something? | Fear of disability / needing surgery | "Will I end up in a wheelchair?" | 「你最擔心啲咩？」 | ~10% |
| Work/social stress | Unable to work, financial concerns | 「膝頭痛有冇影響你返工？」 | ~8% | |
| Health anxiety | Family member had knee replacement / cancer | 「屋企人有冇試過膝頭要做手術？」 | ~5% |
GC Lecture High Yield
OA knee diagnostic criteria (ACR clinical criteria from GC 228): Age > 50 + crepitus + morning stiffness < 30 min + bony enlargement → clinical diagnosis, no bloods needed [1][2].
Knee OA risk factors (GC 228): Age, female sex, obesity, previous knee injury, occupational kneeling, genetic factors [1].
Meniscal tear clinical features (GC 230): Twisting injury → pain + delayed swelling (6–12h) → locking (bucket-handle) → McMurray/Apley test [4].
ACL tear (GC 230): Pivoting/deceleration → audible pop + immediate haemarthrosis + instability → Lachman test (most sensitive) → anterior drawer test [4].
Knee Pain — Family Medicine Clinical Test Note
| Time | Task | Cantonese Key Phrases | Why It Scores Marks |
|---|---|---|---|
| 0:00–0:30 | Greeting, rapport, set agenda | 「你好呀，我係X醫生，今日由我幫你睇症。你可以叫我X醫生。請問點稱呼你？」「今日有咩嘢唔舒服想睇呀？」 | Warm opening, uses patient's name → interpersonal marks |
| 0:30–1:30 | HPI: open → focused | 「可唔可以講多少少，幾時開始痛？邊隻膝頭痛？做乜嘢會痛啲？」「有冇試過隻膝頭鎖住郁唔到？有冇腫？」 | Symptom analysis: onset, site, character, aggravating/relieving, swelling, locking, giving way |
| 1:30–2:30 | Red flags + targeted Qs | 「有冇發燒？有冇成個膝頭又紅又腫又熱？有冇受過傷？夜晚瞓覺會唔會痛醒？有冇唔知點解輕咗好多磅？」 | Screens septic arthritis, tumour, fracture — "must not miss" |
| 2:30–3:30 | PMH, DHx, FHx, Social | 「以前有冇其他病，例如糖尿、痛風、類風濕？食緊咩藥？有冇藥物敏感？屋企人有冇關節炎？你做咩工作？平時做唔做運動？食唔食煙飲唔飲酒？」 | Completes history; occupation/sport crucial for OA/sports injury |
| 3:30–4:30 | ICE + hidden agenda | 「你自己覺得隻膝頭痛係咩原因呀？」(Idea)「你最擔心啲咩？」(Concern)「你今日最希望我幫到你啲咩？」(Expectation)「點解揀今日嚟睇呀？」(Hidden agenda) | ICE is heavily marked; hidden agenda often = functional limitation (e.g. can't climb stairs, exercise, work) |
| 4:30–5:15 | Summarise + signpost | 「等我總結一下：你隻右膝頭痛咗大概三個月，行樓梯特別痛，冇發燒冇受傷，你擔心係唔係退化。我理解嘅啱唔啱？」 | Summarising back scores high interpersonal marks |
| 5:15–6:00 | Explain + safety net + close | 「根據你講嘅情況，我初步覺得最大機會係膝關節退化。我想幫你檢查吓，之後再詳細解釋。如果之後隻膝頭突然好腫、又紅又熱、或者發燒，就要即刻返嚟睇。」 | Demonstrates clinical reasoning; safety-net = marks; polite close |
Uncovering the Hidden Agenda
Ask 「點解揀今日嚟睇呀？」 — The patient may have lived with knee pain for months. The trigger to consult today is often a new functional limitation (can't play with grandchildren, can't go to work, fear of disability/cancer), NOT the pain itself. This is your RFC.
| Domain | English Question | Cantonese Question | Why It Matters | If Positive, Think Of |
|---|---|---|---|---|
| Site | Which knee? Point to where it hurts | 邊隻膝頭痛？可唔可以指俾我睇邊度痛？ | Localisation guides DDx | Medial joint line → meniscus/OA; anterior → patellofemoral; lateral → LCL/IT band |
| Onset | When did it start? Sudden or gradual? | 幾時開始痛？係突然間痛定係慢慢痛起嚟？ | Acute = trauma/crystal/septic; insidious = OA/overuse | Sudden onset → gout, septic arthritis, ligament tear |
| Character | What does the pain feel like? | 痛係點痛法？痠痛定係刺痛？ | Aching/stiffness → OA; sharp/catching → meniscus | |
| Aggravating | Worse with stairs, squatting, walking? | 行樓梯、蹲低、行路會唔會痛啲？ | Stair pain / pain on standing up = patellofemoral OA [1] | Stairs/squatting → patellofemoral; walking → tibiofemoral OA |
| Relieving | Rest helps? Morning stiffness duration? | 休息會唔會好啲？朝早起身有冇覺得膝頭僵硬？僵硬幾耐？ | Morning stiffness > 30 min → inflammatory; < 30 min → OA [2] | > 30 min → RA, PsA; < 30 min → OA |
| Swelling | Any swelling? When did it appear? | 有冇腫？幾時開始腫？ | Immediate haemarthrosis → ACL/fracture; delayed (6–12h) → meniscus [3] | Effusion → intra-articular pathology |
| Locking | Does the knee ever lock? | 隻膝頭有冇試過突然鎖住、伸唔直？ | Locking → bucket-handle meniscal tear or loose body [3][4] | Meniscal tear, OCD, loose body |
| Giving way | Does the knee give way? | 行路有冇覺得隻腳軟、撐唔住？ | Instability → ligament injury, patella subluxation, meniscus [3] | ACL tear, patella subluxation |
| Injury | Any recent trauma? Mechanism? | 有冇受過傷？點樣受傷？有冇扭到？ | Mechanism predicts structure injured | Twist + pop → ACL; valgus blow → MCL; direct blow tibia → PCL [3] |
| Red flag: infection | Fever? Red hot swollen joint? | 有冇發燒？隻膝頭有冇又紅又腫又熱？ | Septic arthritis = emergency; do NOT miss | Septic arthritis |
| Red flag: tumour | Night pain? Weight loss? | 夜晚瞓覺會唔會痛醒？有冇輕咗好多磅？ | Night pain + weight loss → bone tumour/metastasis | Primary bone tumour, metastasis |
| Red flag: neurovascular | Numbness, tingling, coldness? | 有冇痺、冇感覺、或者隻腳凍咗？ | Vascular/neurological compromise | Popliteal artery injury, nerve entrapment |
| Gout risk | History of gout? Diet (beer, organ meat)? Meds? | 以前有冇痛風？鍾唔鍾意飲啤酒、食內臟？食緊咩藥？ | Acute monoarthritis + risk factors = gout [5] | Gout, pseudogout |
| PMH | DM, RA, gout, psoriasis, IBD? | 有冇糖尿、類風濕、痛風、牛皮癬、腸炎？ | Comorbidities change DDx | RA, PsA, reactive arthritis |
| DHx | Current medications, anticoagulants? | 食緊咩藥？有冇食薄血丸？ | Anticoagulant → haemarthrosis; diuretics → gout | |
| Allergy | Drug allergy? | 有冇藥物敏感？ | Safety; marks | |
| FHx | Family history of arthritis, gout? | 屋企人有冇關節炎或者痛風？ | OA, RA, gout have familial tendency | |
| Occupation | What is your job? Standing/kneeling? | 你做咩工作？要唔要企好耐或者跪？ | Occupational load → OA risk; functional impact | OA, prepatellar bursitis |
| Exercise/Sport | What sports do you play? | 平時做咩運動？ | Sport-specific mechanism → specific injury pattern [4] | ACL (pivoting sport), meniscus (twist), runner's knee |
| Functional impact | Can you manage stairs, shopping, work? | 而家行唔行到樓梯？買到嘢？返唔返到工？ | Functional limitation = social/psychological problem for CRF | |
| Mood | Has the pain affected your mood/sleep? | 隻膝頭痛有冇影響你心情或者瞓覺？ | Screen psychological impact for biopsychosocial | Depression, anxiety, sleep disturbance |
Case Report Form Answer Builder
Write: "Knee pain for [duration]"
High-yield HPI points to capture:
- SOCRATES: Site (which knee, localisation), Onset (acute/gradual), Character, Radiation, Aggravating (stairs/walking/sport), Timing (morning stiffness duration), Exacerbating/relieving, Severity
- Swelling: timing (immediate vs delayed), recurrent?
- Mechanical symptoms: locking, giving way, clicking
- Trauma/injury history + mechanism
- Red flags screened: fever, night pain, weight loss
- Functional impact: stairs, walking distance, work, ADLs
- PMH, DHx, FHx, occupation, sports, smoking/alcohol
The RFC is NOT "knee pain" — it is WHY the patient came TODAY.
| Likely RFC Examples | How to Phrase |
|---|---|
| Functional limitation | "Unable to climb stairs / walk to market for the past 2 weeks" |
| Fear of serious disease | "Worried the knee pain may be cancer / arthritis requiring surgery" |
| Wants investigation | "Wants X-ray to check if the knee is 'worn out'" |
| Pain affecting work | "Knee pain preventing the patient from working" |
| Social trigger | "Daughter's wedding in 2 months, wants to be able to walk comfortably" |
| Component | Example Wording |
|---|---|
| Idea | "Patient thinks the pain is due to 'bone wearing out' / ageing / 退化" |
| Concern | "Worried about needing knee replacement surgery" OR "Worried about cancer" OR "Worried about becoming disabled and being a burden" |
| Expectation | "Wants X-ray to confirm diagnosis" OR "Wants pain relief" OR "Wants referral to orthopaedic surgeon" |
For a typical FM station (middle-aged/elderly patient, gradual onset, use-related knee pain, no trauma, no red flags):
Most likely: Knee osteoarthritis [1][2]
Minimum supporting evidence to write:
- Age > 50
- Gradual onset, use-related pain (worse with activity, better with rest)
- Morning stiffness < 30 minutes
- Crepitus on examination
- ± Bony enlargement, ± restricted ROM
- No features of inflammatory arthritis (no prolonged morning stiffness, no systemic features)
If a young active patient with trauma history → consider meniscal tear or ligament injury
| DDx | Key Discriminator |
|---|---|
| 1. Meniscal tear | Mechanical locking/catching, joint-line tenderness, +ve McMurray test; history of twisting injury or degenerative in elderly [3][4] |
| 2. Gout / crystal arthropathy | Acute onset, extremely painful, red/hot/swollen single joint, history of gout, raised urate, resolves in 7–10 days [5] |
| 3. Referred hip OA | Anterior knee pain but limited hip internal rotation on exam; normal knee exam; groin pain if you specifically ask [1] |
Alternatives if the stem suggests a young/sports patient:
- ACL tear (pop + haemarthrosis + Lachman +ve)
- Patellofemoral pain syndrome (anterior knee pain, worse stairs/prolonged sitting)
- Osgood-Schlatter disease (adolescent, tibial tuberosity tenderness) [7]
| Domain | Problem |
|---|---|
| Biological | Knee osteoarthritis causing chronic pain and restricted mobility |
| Psychological | Anxiety about progressive disability / fear of needing surgery; low mood from chronic pain and reduced activity |
| Social | Functional limitation affecting work (e.g. occupation requiring standing/walking), reduced social participation (can't go to yum cha / exercise with friends), increased dependence on family |
| Diagnosis/DDx | Best Supporting Physical Sign | How to Elicit | Why It Supports This Diagnosis |
|---|---|---|---|
| Knee OA (most likely) | Crepitus on knee flexion/extension [1][2] | Place hand over patella while patient actively flexes and extends knee; feel for grating sensation | Indicates patellofemoral cartilage degeneration; part of ACR clinical criteria for knee OA |
| Knee OA (alternative sign) | Bony enlargement / osteophytes | Palpate around joint margins for hard bony swelling | Bony enlargement = osteophyte formation; hallmark of OA vs soft tissue swelling of inflammatory arthritis |
| Meniscal tear | Joint-line tenderness ± McMurray test +ve | Palpate medial/lateral joint line with knee at 90° flexion; McMurray: flex → rotate → extend while feeling for click [4][9] | Joint-line tenderness is most sensitive clinical sign for meniscal tear; McMurray click is specific |
| Gout | Acutely inflamed joint (red, hot, swollen, exquisitely tender) | Inspection + palpation of knee; look for tophi on ears/elbows/hands | Acute monoarthritis with intense inflammation suggests crystal arthropathy |
| ACL tear | Lachman test +ve (anterior laxity at 20° flexion) [3][4] | Patient supine, knee flexed 20°; stabilise femur, pull tibia anteriorly; +ve = soft endpoint with excessive anterior translation | Most sensitive clinical test for ACL tear [4] |
| Referred hip pain | Limited internal rotation of ipsilateral hip | Patient supine, flex hip and knee to 90°, internally rotate hip; compare sides | If knee exam is normal but hip ROM is limited, knee pain is likely referred from hip pathology |
| Septic arthritis | Warm, tense effusion with erythema + fever | Inspect (redness, swelling), palpate (warmth, effusion — patellar tap / bulge test), check temperature | Hot joint + fever + unable to weight-bear = septic arthritis until proven otherwise — EMERGENCY |
Exam Discriminators and Traps
Top Traps That Lose Marks
- Forgetting to examine the hip — Hip pathology (especially OA) commonly refers pain to the knee [7]. Always ask about hip/groin pain and check hip ROM. The exam loves this pitfall.
- Missing septic arthritis — An acutely hot, swollen joint with fever is septic until proven otherwise. Requires URGENT aspiration and referral. Do NOT give antibiotics before aspiration if possible.
- Writing "knee pain" as the RFC — The RFC must be the reason the patient came TODAY, not the symptom itself. Dig deeper.
- Not asking about morning stiffness duration — This single question separates OA (< 30 min) from inflammatory arthritis (> 30 min). High yield on CRF.
- Confusing immediate vs delayed swelling — Immediate (within 2h) = haemarthrosis (ACL tear, fracture). Delayed (6–12h) = meniscal tear, effusion [3][4].
- Forgetting ICE — Many students focus too much on clinical questions and forget to ask ICE explicitly. This is a heavily marked CRF section.
- Not screening for occupation and functional impact — These feed directly into the biopsychosocial problems and RFC.
| Red Flag | Suggests | Action |
|---|---|---|
| Hot, red, swollen joint + fever + unable to weight-bear | Septic arthritis | Same-day referral to A&E; joint aspiration before antibiotics |
| Night pain + weight loss + bony mass | Bone tumour / metastasis | Urgent X-ray + ortho/oncology referral |
| Acute trauma + unable to weight-bear + deformity | Fracture | X-ray + ortho referral |
| Acute locked knee (unable to extend) | Bucket-handle meniscal tear | Ortho referral (may need urgent arthroscopy) |
| Acute severe knee swelling post-trauma (haemarthrosis) | ACL tear / fracture | X-ray ± MRI, ortho referral |
For OA knee in FM: "我會建議你先減少衝擊性運動，控制體重，做物理治療加強大腿肌肉。痛嘅時候可以食撲熱息痛。如果之後隻膝頭突然好腫、又紅又熱、或者發燒，就要即刻返嚟睇。"
(Advise activity modification, weight management, physiotherapy/quadriceps strengthening, simple analgesia; safety-net: return if acute hot swollen joint or fever.)
High Yield Summary
What to ASK: SOCRATES for knee pain; mechanical symptoms (locking, giving way, clicking); swelling timing; trauma mechanism; morning stiffness duration (< 30 min = OA, > 30 min = inflammatory); red flags (fever, night pain, weight loss); hip pain (referred!); occupation; sport; functional impact; ICE + hidden agenda.
What to WRITE on CRF:
- CC/HPI: "R/L knee pain × [duration], [gradual/acute] onset, [aggravating factors], [mechanical symptoms], [red flags negative]"
- RFC: The functional or psychological trigger that brought the patient today, NOT "knee pain"
- ICE: Explicitly document idea, concern, expectation
- Most likely Dx: Knee OA (if typical) with supporting criteria (age > 50, crepitus, morning stiffness < 30 min, usage pain)
- DDx: Meniscal tear, gout/crystal arthropathy, referred hip OA (adjust for the stem)
- Biopsychosocial: Bio = OA/pain; Psych = fear of disability/surgery/low mood; Social = work limitation/social isolation
- Physical sign: Crepitus on knee flexion-extension
What NOT to MISS: Septic arthritis (hot joint + fever = emergency), referred hip pain, and the hidden agenda.
Active Recall - Family Medicine Clinical Test
[1] Lecture slides: GC 228. Knee Osteoarthritis_Part A.pdf [2] Lecture slides: GC 228. Knee Osteoarthritis_Part B.pdf [3] Senior notes: Maksim Surgery Notes.pdf (Knee Ligament and Meniscal Injuries, p.257–258) [4] Lecture slides: GC 230. Knee Sport Injuries_Part 1.pdf; GC 230. Knee Sport Injuries_Part 2.pdf [5] Senior notes: Block A - Painful red joint_ monoarthropathy, gouty arthritis, septic arthritis, haemarthrosis.pdf [6] Senior notes: Block A - Leg swelling and chest pain_ deep vein thrombosis; pulmonary embolism; Thrombophilia.pdf [7] Senior notes: Adrian Lui Pediatrics Notes.pdf (Knee Pain, p.448) [8] Senior notes: Ryan Ho Cardiology.pdf (Intermittent Claudication, p.205) [9] Lecture slides: LL exam Clinical Skill Practice Session 2023.pdf (Knee clinical assessment, p.62–78)
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