Lachman test
With the knee slightly bent, the examiner assesses forward translation of the shin bone; this is generally considered the most sensitive manual test for ACL rupture.
Assessment of a suspected ACL injury typically begins with a detailed history of the injury mechanism, since a pivoting or landing mechanism with an audible pop is highly characteristic, followed by observation of swelling and a careful ligament examination.
Because associated injuries are common, clinicians also examine the menisci and collateral ligaments, and imaging is frequently used to confirm the diagnosis and map the full extent of injury before deciding on management.
Assessment tests
Anterior drawer test
With the knee bent to about 90 degrees, the examiner pulls the shin bone forward to assess for excessive anterior translation, though it is generally considered less sensitive than the Lachman test.
Pivot shift test
This dynamic test reproduces the sensation of the knee shifting during a pivoting movement and helps assess functional rotational instability.
McMurray test
Combining rotation with bending and straightening the knee helps identify concurrent meniscus damage, which is common alongside ACL tears.
Hop and single-leg strength testing
Later in rehabilitation, hop tests and strength comparisons between limbs are used to gauge readiness for progressively more demanding activity.
Red flags
These warrant prompt clinical review rather than unsupervised exercise progression.
Locked knee or inability to fully extend
A knee that cannot be fully straightened after injury may indicate a displaced meniscus fragment and should be evaluated promptly.
Signs of associated fracture
Significant bony tenderness or deformity after a high-energy injury raises concern for an associated fracture requiring imaging.
Gross knee instability with minimal force
A knee that feels grossly unstable even during simple daily movements suggests a more complex ligamentous injury requiring specialist evaluation.
Signs of compromised circulation
A cold, pale, or pulseless lower leg after a high-energy knee injury is a surgical emergency requiring immediate care.
A thorough combination of history, ligament-specific testing, and imaging generally allows a confident diagnosis and helps guide the shared decision between surgical reconstruction and structured non-surgical rehabilitation.
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