Slocum test: How to perform, interpret and record it

The Slocum test is a knee drawer test performed with the tibia rotated. It checks for rotatory instability, most often after an ACL injury. Slocum and colleagues described it in the 1970s, and it uses two positions. With the knee flexed to about 90 degrees, you pull the tibia forward in 30° internal rotation, then in 15° external rotation.

More forward shift than on the other knee points to anterolateral or anteromedial rotatory instability. That tells you which structures beyond the ACL may be damaged, so it shapes referral and rehab plans. Below, we walk through the setup, how to read each position, the mistakes that skew results and how to write it up.

Key takeaways

The Slocum test is an anterior drawer performed with the tibia rotated, used to check rotatory knee instability.

Test at 30° internal rotation for anterolateral instability and 15° external rotation for anteromedial instability, with the knee flexed to about 90 degrees.

Hamstring guarding, a sliding foot and over-rotation are common reasons for a false negative.

A positive result supports a diagnosis but does not replace imaging or clinical judgment.

Record the version used, both rotation positions and the side-to-side comparison so results stay comparable over time.

What the Slocum test tells you about a knee

The Slocum test shows whether the knee is unstable in rotation, not only in a straight line. It targets anterolateral rotatory instability (ALRI), where the lateral tibial plateau subluxes forward as the tibia rotates. The external rotation position adds a check for anteromedial rotatory instability (AMRI).

You’d reach for it when an ACL injury is suspected. Once the ACL is compromised, the capsule and collateral structures become key secondary restraints. Rotation shows you which of them are still holding. The test works best as one part of a full knee examination, alongside history, palpation and other ligament tests.

Set the knee up before you pull

The patient lies supine with the knee flexed to about 90 degrees and the foot fixed on the couch. Many examiners sit lightly on the forefoot to hold it in place. Your hands wrap around the upper tibia, with your thumbs on the joint line.

1. Position the patient supine and check that the hamstrings are relaxed.
2. Flex the knee to about 90 degrees and fix the foot on the couch.
3. Rotate the tibia internally to about 30 degrees and apply an anterior pull.
4. Repeat with the tibia externally rotated to about 15 degrees, noting any difference.
5. Test the other knee the same way, then compare translation, end feel and any pain or apprehension.

Keep the force gentle and controlled. Stop if the patient reports sharp pain or marked apprehension, because either can change the result and may call for imaging.

Before-you-test checklist

• Ask about the injury mechanism, swelling and any giving-way episodes first.
• Look for a large effusion, which can block translation and hide laxity.
• Examine the uninjured knee first so you both know what normal feels like.
• Explain each step, since an anxious patient guards with the hamstrings.
• Confirm the foot is fixed in the right rotation before every pull.

Reading a positive result in each rotation

A positive Slocum test means more forward shift than on the uninjured side in that rotation. Clinicians usually grade it by how much extra translation they feel and whether the endpoint is firm or soft.

The table below sets out what each position stresses.

A finding at 30° internal rotation alone points to anterolateral laxity. A finding at 15° external rotation alone points to anteromedial laxity, which involves the medial structures as well as the ACL. Positive results in both positions suggest wider involvement.

The diagram below puts the setup and both positions side by side.

The modified version is a pivot shift variant

The modified Slocum test is a side-lying, gravity-assisted version of the lateral pivot shift. Despite the name, it is not a side-lying drawer. The patient lies on the unaffected side with the pelvis rotated about 30° backward. The affected knee starts at about 10° of flexion.

You then apply a valgus force while flexing the knee. In a positive test, the subluxed tibia reduces at about 40° of flexion. Gravity does some of the work, which can help with a larger patient. Its diagnostic value is unproven, though, so note which version you used in the record.

Common mistakes that skew the result

False negatives often come from technique as much as from the knee itself. These are the errors worth checking for:

• Hamstring guarding holds the tibia back and masks laxity, so relax the patient and recheck.
• Over-rotating the tibia tightens intact structures and can damp the shift. Stay close to 30° and 15°.
• A foot that slides lets the whole leg move, which can feel like translation.
• Skipping the other knee leaves you without a baseline, and normal laxity varies between people.
• Testing through a tense effusion can block movement and hide instability.

How it compares with the pivot shift and drawer tests

The lateral pivot shift test is a related rotatory test that is widely used to confirm ALRI. It is routinely done with the patient awake. Even so, guarding often limits the awake pivot shift, especially soon after injury. The modified Slocum is itself a pivot shift variant.

The anterior drawer test uses the same 90° knee position with the tibia in neutral. It measures straight anterior translation, while the Slocum test adds rotation. Run them together and you see both the size and the direction of the laxity.

Sensitivity and specificity are thinly researched

Reliable sensitivity and specificity figures for the Slocum test are hard to find. It has rarely been included in diagnostic accuracy studies, so its clinical value is still debated. Treat it as one test in a battery, and check primary research before quoting any figure.

The Physiopedia entry on Slocum’s test summarizes the procedure and the structures each position stresses.

Limits and when to refer for imaging

Patient cooperation, guarding, pain and examiner experience all affect the result. A negative test does not rule out a ligament injury. Equally, a positive test does not confirm a rupture.

• Refer for imaging when the history or exam suggests a significant ligament injury.
• Avoid forceful testing in an acutely painful or unstable knee.
• Document any contraindication, and why the test was modified or left out.

If you’re running a broader screen, an orthopedic examination template keeps the Slocum result next to your other findings.

Documenting Slocum test findings in a SOAP note

Record the test in the objective section. State the version, the knee tested, both rotation positions and the side-to-side comparison. Then link the finding to your assessment and plan, so the next clinician can follow your reasoning.

Example objective entry: Slocum test, supine, right knee. At 30° internal rotation, increased anterior translation compared with the left, soft endpoint, no pain. At 15° external rotation, symmetrical with the left, firm endpoint. Mild hamstring guarding settled with cueing.

If your team works from shared physical therapy SOAP notes, use the same fields every visit. That makes changes in laxity easy to track across sessions.

How Pabau keeps knee test findings consistent

In many practices, special test results end up on paper forms or in free-text notes. Each clinician writes them a little differently, so comparing visits means reading between the lines.

Pabau, the practice management platform we build, lets you turn this checklist into a structured clinical note. Pabau Scribe, our AI scribe, is built into the platform and drafts the note from your consultation. Patients can also complete digital forms before the visit, so their injury history is ready when they arrive.

Each result then sits in one patient record, next to appointments and earlier notes. That’s the job of good physical therapy EMR software, so you can see at a glance whether rotatory laxity is improving.

Record knee special tests the same way every time

Pabau’s clinical notes, Pabau Scribe and digital forms keep Slocum test findings structured and comparable across visits. Every result lands in one patient record, ready for the next clinician.

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Conclusion

The Slocum test earns its place when you run it the same way every time. Get the rotations right, 30° internal and then 15° external, and keep the foot fixed. Always compare against the other knee.

A clear positive tells you which side of the knee needs a closer look, and when to refer. A negative result in a guarded patient deserves a retest, not reassurance. Book a demo to see how Pabau keeps your knee exam findings structured and easy to compare.

Continue your research

Seeing laxity in the opposite direction? Reverse pivot shift test explains the technique, interpretation and accuracy.

Suspect the posterolateral corner? Posterolateral drawer test covers technique, grading and pitfalls.

Worried about the meniscus too? Thessaly test shows how to perform it and avoid false positives.

Tracking function after a knee injury? Knee outcome survey gives you a scored patient-reported measure.

Deciding whether to X-ray? Ottawa knee rules sets out the five criteria and how to apply them.

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