Why the Knee Is a High-Yield OSCE Examination
The knee is the most commonly examined joint in orthopaedic OSCE stations. Examiners want to see a confident, systematic approach — Look, Feel, Move — followed by purposeful special tests. The most common mistake is jumping straight to special tests without completing the basic examination first.
Setup
- Wash hands, introduce, confirm name and DOB, gain consent
- Expose both legs fully to the mid-thigh — always compare sides
- Ask about pain before touching: "Before I start, can you point to where the pain is?"
- Begin with the patient standing, then move to lying supine
Look — Inspect From All Sides
Standing (weight-bearing):
- Gait — antalgic gait (shortened stance phase on painful side)?
- Alignment — valgus (knock-knee) or varus (bow-leg)?
- Muscle wasting — compare quadriceps bulk bilaterally
Lying supine:
- Skin: scars (arthroscopy portals, medial/lateral incisions), erythema, bruising, swelling
- Shape: loss of normal contours, effusion (fullness in suprapatellar pouch, obliteration of medial dimple)
- Deformity: fixed flexion deformity (cannot fully extend)
Feel — Palpate Systematically
- Temperature: compare bilaterally using the dorsum of the hand
- Effusion tests:
🧠 Mnemonic
Two effusion tests — choose by suspected volume
Patellar tap: for moderate-to-large effusions (over 30 ml). Empty suprapatellar pouch with one hand, then ballotte the patella — positive if it bounces back
Bulge sign (sweep test): for small effusions (5–10 ml). Sweep medial compartment upward, then stroke down the lateral side — positive if a bulge appears medially
- Joint line: palpate medial then lateral — localised tenderness = meniscal pathology
- Bony landmarks: tibial tuberosity (Osgood-Schlatter), patella, fibular head
- Collateral ligaments: along their full courses medially and laterally
- Popliteal fossa: Baker's cyst, lymphadenopathy
Move — Active Then Passive Range of Motion
| Movement | Normal range | What to note |
|---|---|---|
| Extension | 0° | Fixed flexion deformity if unable to reach full extension |
| Hyperextension | 5–10° | Excessive = ligamentous laxity |
| Flexion | 130–145° | Reduced in OA, effusion, post-surgery |
Ask the patient to straighten and bend the knee actively first, then passively guide them through the full range. Note pain, crepitus (OA), and the endpoint feel.
Special Tests — A, P, M, C
🧠 Mnemonic
APMC — the order for knee special tests
A — ACL (Lachman, anterior drawer)
P — PCL (posterior sag, posterior drawer)
M — Menisci (McMurray, Thessaly)
C — Collaterals (valgus stress = MCL, varus stress = LCL)
ACL
- Lachman test (most sensitive, ~85%): flex knee 20–30°, stabilise femur, pull tibia anteriorly — positive if excessive anterior translation with soft or absent endpoint
- Anterior drawer: knee at 90°, sit on foot, pull tibia forward
PCL
- Posterior sag sign: flex both knees to 90°, feet flat — tibia sags posteriorly on affected side
- Posterior drawer: same setup as anterior drawer, push tibia backward
Menisci
- McMurray test: flex knee fully, externally rotate foot + extend knee = medial meniscus; internally rotate + extend = lateral meniscus — positive if click or pain at joint line
- Thessaly test (most sensitive): patient stands on affected leg, knee at 20° flexion, rotates body — positive if joint line pain or locking
Collateral Ligaments
- Valgus stress (MCL): apply valgus force at 0° then 30° — laxity at 30° = MCL tear; laxity at 0° = more extensive injury
- Varus stress (LCL): apply varus force at 0° then 30°
💎 Clinical Pearl
Always test collaterals at both 0° and 30° of flexion. At full extension, the posterior capsule and cruciates provide secondary stabilisation — testing at 30° slackens these and isolates the collateral ligament.
To Complete
- Neurovascular: sensation (L3/L4), dorsalis pedis and posterior tibial pulses, capillary refill
- Hip: always examine — hip OA and AVN commonly refer pain to the knee
- Investigations: weight-bearing AP and lateral X-rays, skyline view for patellofemoral joint; MRI for soft tissue injuries
How to Present
"On examination, [patient] walked with an antalgic gait. On inspection supine, there was a moderate effusion with a positive patellar tap. The medial joint line was tender. Range of motion was limited in flexion to 100° with crepitus. McMurray's test was positive for medial meniscal pathology. Lachman's test was negative. My findings are consistent with a medial meniscal tear with a reactive effusion. I would request weight-bearing X-rays and an MRI of the knee."
Frequently Asked Questions
"What is the most sensitive test for an ACL tear in an OSCE?"
The Lachman test is the most sensitive clinical test for ACL integrity (approximately 85% sensitive). It is performed with the knee at 20–30° flexion, which relaxes the posterior capsule and isolates the ACL. A positive result is excessive anterior tibial translation with a soft or absent endpoint.
"How do you test for a knee effusion in an OSCE?"
Use the patellar tap for moderate-to-large effusions: empty the suprapatellar pouch and then ballotte the patella — a positive tap means the patella bounces back. For small effusions, use the bulge (sweep) sign: sweep the medial compartment upward then stroke down the lateral side — a positive result is a visible medial bulge.
"What does medial joint line tenderness indicate?"
Medial joint line tenderness is the most consistent clinical sign of medial meniscal pathology. Combining it with a positive McMurray or Thessaly test significantly increases diagnostic accuracy. It can also indicate medial compartment osteoarthritis.
"Why do you test ligaments at both 0° and 30° of knee flexion?"
At full extension, the posterior capsule and cruciate ligaments provide secondary stabilisation even when a collateral is torn, masking the laxity. Testing at 30° slackens these secondary stabilisers and isolates the collateral ligament, making the test more specific and the laxity more apparent.
"What do you say to complete the knee examination in an OSCE?"
State you would like to assess the hip (hip pathology commonly refers to the knee), examine the ankle, assess neurovascular status distally, request weight-bearing AP and lateral X-rays, and arrange an MRI if soft tissue injury is suspected clinically.
Related guides: [Musculoskeletal History OSCE](/blog/musculoskeletal-history-osce) · [Hand Examination OSCE](/blog/hand-examination-osce) · [Peripheral Vascular Examination OSCE](/blog/peripheral-vascular-examination-osce)