Write a short note on Clinical Tests for Knee Injuries.
Purpose
A systematic set of clinical tests assesses the ligaments and menisci of the injured knee and, together with the history and MRI, guides diagnosis. Each test stresses a specific structure.
| Test | Structure / meaning |
|---|---|
| Lachman’s | ACL (most sensitive) — anterior tibial glide at 20–30° flexion |
| Anterior drawer | ACL — anterior glide at 90° flexion |
| Pivot-shift | ACL — rotational instability (giving way) |
| Posterior drawer / sag | PCL — posterior tibial displacement |
| Valgus / varus stress | MCL / LCL |
| McMurray’s | Meniscal tear — pain/click on rotation |
Key Tests Explained
- Lachman’s test (the most sensitive for the ACL) assesses anterior tibial translation with the knee flexed ~20–30°. The anterior drawer tests the ACL at 90° and the posterior drawer/sag sign tests the PCL.
- Valgus and varus stress tests assess the collateral ligaments.
- McMurray’s test (rotating the flexed knee while extending it) elicits pain or a click with a meniscal tear, supported by joint-line tenderness.
CLINICAL PEARL
Lachman’s test is the most sensitive clinical test for an ACL tear — more so than the anterior drawer, because it is done in slight flexion where hamstring guarding is less.
Clinical Note
No single test is perfect, so the structures are examined in combination and always compared with the normal side, since a degree of laxity is individual; guarding from pain and swelling can mask instability in the acute knee, which is why examination is sometimes repeated once the acute phase has settled, and why MRI is a valuable adjunct for confirming ligament and meniscal injury.
CLINICAL PEARL
When you have only one test to trust for the ACL, choose Lachman’s — done in slight flexion, it is the most sensitive because hamstring guarding is minimised.
DANGER / REMEMBER
Because pain and muscle guarding can mask instability in the freshly injured knee, a normal-feeling examination immediately after injury does not exclude a ligament tear; the tests are therefore repeated once swelling settles, and an examination under anaesthesia or MRI is used when clinical doubt persists.
Lachman test is the most sensitive for ACL injury.
KEY POINT
Key points TO remember
- Lachman’s (most sensitive) & anterior drawer & pivot-shift → ACL.
- Posterior drawer / sag → PCL; valgus/varus stress → MCL/LCL.
- McMurray’s + joint-line tenderness → meniscal tear.
- Combine tests with history and MRI to localise the injury.
EXAM TIP
Sources: Maheshwari's Essential Orthopaedics; Apley & Solomon's System of Orthopaedics and Trauma; AO Principles of Fracture Management.
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