Elson test: How to perform and interpret it for central slip injuries

The Elson test is a bedside examination that detects rupture of the central slip of the extensor tendon at the proximal interphalangeal (PIP) joint.

It takes under a minute to perform. With the PIP held at 90 degrees of flexion, a positive result shows rigid hyperextension at the DIP joint alongside weak or absent PIP extension.

Miss the injury and the patient develops boutonniere deformity. That is a fixed flexion contracture at the PIP joint, and it is far harder to treat than the rupture that caused it.

No published study reports a sensitivity or specificity for the Elson test, which is worth knowing before you lean on the result. This guide covers the anatomy, the technique, how to read both joints, where the test misleads you, and what to do after a positive finding.

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Key takeaways

The Elson test identifies central slip rupture by detecting whether extension force travels through the lateral bands instead of the central slip.

A positive result shows rigid DIP extension with weak or absent PIP extension when the PIP joint is held at 90 degrees of flexion.

No published study reports a sensitivity or specificity for the test, so clinical judgment still decides the borderline cases.

False negatives happen when the central slip and both lateral bands are cut together, which is why open wounds need exploration.

Untreated central slip injuries progress to boutonniere deformity, and closed injuries are splinted in PIP extension for six to eight weeks.

What the Elson test is and why it matters

The Elson test is a physical examination maneuver that shows whether the central slip of the extensor digitorum tendon is intact or ruptured. Elson first described it in 1986. It works by exploiting the anatomy of the extensor mechanism at the PIP joint.

Flex the PIP joint to 90 degrees and ask the patient to extend it. An intact central slip drives the middle phalanx into extension and leaves the DIP joint passively mobile. A ruptured central slip sends that force through the lateral bands instead, and they pull the distal phalanx into rigid hyperextension.

The test matters because zone III extensor injuries, at or just proximal to the PIP joint, are easily underestimated at first presentation. Swelling, pain, and limited range of motion after a jammed finger or a laceration look identical whether the central slip is intact or not.

Without a structured assessment, missed injuries go on to develop boutonniere deformity within three to six weeks as the lateral bands migrate volarly.

Anatomy of the extensor mechanism and the central slip

Reading the Elson test correctly depends on knowing what the extensor mechanism does at the PIP joint. The extensor digitorum tendon splits into three terminal slips over the proximal phalanx.

• Central slip: inserts into the dorsal base of the middle phalanx and is responsible for active PIP extension.
• Lateral bands (two): pass on either side of the PIP joint and reunite distally to insert into the distal phalanx, extending the DIP joint.
• Triangular ligament: connects the two lateral bands dorsally and holds them in position on the back of the finger.

When the central slip ruptures, the triangular ligament also fails over time. The lateral bands then migrate volarly, toward the palm, which converts them from DIP extensors into PIP flexors. That volar shift is the pathomechanical basis of boutonniere deformity, and the Elson test catches the force redistribution before the deformity sets.

Extensor tendon zone III covers injuries at the level of the PIP joint itself. Zone II covers the middle phalanx and zone IV the proximal phalanx. Zone III is the one the Elson test addresses.

Indications: When to test for a central slip injury

Test whenever a patient presents with a PIP joint injury and you cannot confirm central slip integrity by observation alone. Four presentations should prompt it every time.

• A forced flexion injury, most often a jammed finger
• A direct blow to the dorsum of the PIP joint
• A dorsal PIP dislocation, even after a successful reduction
• Any dorsal laceration over the PIP joint, whatever its apparent depth

Sports medicine services see a disproportionate share of these injuries. Athletes minimize symptoms and return to play before anyone examines the finger properly. Practices running sports medicine software can make the central slip check a required field on finger injury notes.

The test also earns its place at follow-up. Repeat it before removing a splint to confirm that a confirmed or suspected central slip injury has healed. Post-reduction assessment of dorsal PIP dislocations is the highest-yield indication of all, because the reduction itself masks how much soft tissue was disrupted.

How to perform the test, step by step

Performing the test correctly requires precise positioning. Examiner technique decides whether the result means anything.

1. Position the hand. Ask the patient to rest the affected hand palm-down on the edge of a firm surface. The finger being tested should extend beyond the edge so the PIP joint can flex freely.
2. Flex the PIP joint to 90 degrees. Bring the injured finger over the table edge until the PIP sits at a right angle. The DIP joint must stay free and unsupported.
3. Stabilize the proximal phalanx. Hold it firmly against the table with your thumb and index finger. This stops the patient extending the finger through wrist extension or intrinsic muscle recruitment, which would give a false negative.
4. Ask for active extension. Instruct the patient to straighten the PIP joint against gravity or gentle resistance. Watch both joints while they do it.
5. Read the PIP and DIP together. Note the force generated at the PIP joint and how the DIP joint behaves. Those two observations together give you the result.

The whole test takes under a minute. Poor stabilization of the proximal phalanx is the single most common technical error, because intrinsic muscles then recruit and mask weak PIP extension.

Interpreting the result: Positive, negative, and equivocal

Interpretation depends on reading two joints at once, not one in isolation. The table below sets out the expected findings and the anatomy behind each one.

The physiology behind it is straightforward. With the PIP joint held at 90 degrees, a ruptured central slip cannot generate extension force across that joint at all. The effort is channeled entirely through the lateral bands, which pull the distal phalanx into rigid hyperextension.

An intact central slip transmits force to the middle phalanx and produces strong active PIP extension. The lateral bands stay slack, so the DIP joint remains passive and mobile.

A DIP joint that springs into rigid extension rather than staying relaxed is the most reliable positive sign. Weak PIP extension on its own is not enough, because pain inhibition produces the same finding with an intact central slip.

How reliable is the Elson test?

No published study reports a sensitivity or specificity for the Elson test. Clinicians rely on it because the mechanism is sound and the alternative is missing the injury. No diagnostic accuracy study has measured it against surgical findings.

The paper most often cited for those figures does not contain them. A 2021 cadaveric study in the Journal of Hand Surgery (Global Online) measured force and range of motion changes in fingers under cyclic loading. Its authors reported that the change in DIP resistance was likely imperceptible clinically.

Treat that honestly at the bedside. A positive test is strong evidence of rupture. A negative test is much weaker evidence that the central slip is intact, and neither result carries a number you can quote.

Several factors degrade the test in a live patient compared with a cadaver finger.

• Pain inhibition: a patient in acute pain cannot generate maximal extension effort, which flattens the force difference between the two joints.
• Edema: swelling around the PIP joint can mechanically limit DIP extension even with an intact central slip, producing a false positive.
• Examiner technique: without firm stabilization of the proximal phalanx, intrinsic muscles recruit and mask weak PIP extension.
• Partial tears: a partly torn central slip still transmits some force, so the result reads as equivocal rather than positive.
• Very early presentation: within the first few hours, hematoma can limit all movement before the force redistribution pattern appears.
• Positioning: a PIP held short of 90 degrees changes the tension in the lateral bands, and the result with it.

Treat an equivocal result with a plausible mechanism as positive until proven otherwise. Splinting carries minimal downside. A missed central slip injury does not.

When the test fails: The false-negative trap

The failure that matters clinically is a false negative caused by simultaneous laceration of the central slip and both lateral bands. A 2022 case report in PubMed Central documented exactly that presentation. Neither structure could transmit extension force, so the DIP joint did not rigidly extend and the test read as negative.

This pattern belongs to open lacerations where the wound track crosses both dorsal structures. Closed crush and jamming injuries usually spare the lateral bands. So never rely on the Elson test alone for an open dorsal PIP laceration.

Surgical exploration is indicated whatever the test shows, once the wound depth and location are consistent with an extensor mechanism injury.

The modified Elson test

The modified Elson test is a passive alternative for patients who cannot comply with active extension because of pain or cooperation difficulties. The examiner does not ask for active extension. Instead they passively flex and extend the DIP joint while the PIP stays at 90 degrees over the table edge.

In the modified version, a ruptured central slip shows as increased passive DIP stiffness on attempted passive flexion. The lateral bands bear tension from the attempted PIP extension, so the DIP joint feels noticeably stiffer than the same finger on the uninjured hand. An intact central slip leaves the lateral bands slack and the DIP joint supple.

The modified test suits children, patients in severe pain, and anyone assessed under local anesthetic where active cooperation is unreliable. It does not replace the standard test when the patient can cooperate. Passive stiffness is more subjective and needs a comparison with the other hand. Record which version you used and what you found, since the two do not produce interchangeable evidence.

Boutonniere deformity: The consequence of a missed central slip injury

Boutonniere deformity is the predictable end stage of an untreated central slip rupture. The finger settles into PIP flexion with DIP hyperextension, the inverse of normal posture.

The sequence runs like this. Once the central slip fails, the PIP joint loses active extension. The triangular ligament attenuates, so the lateral bands are no longer held dorsally and displace toward the palm.

Once they sit volar to the axis of the PIP joint, the lateral bands switch function and flex the joint they used to extend. At the same time they tighten on the distal phalanx and pull the DIP into hyperextension.

The deformity typically becomes apparent three to six weeks after the injury if the central slip is not immobilized. Once it is fixed, correction needs prolonged splinting, serial casting, or surgical release. That timeline is why an accurate reading on day one is worth the minute it costs.

Management after a positive Elson test

A positive Elson test dictates immediate management, and the pathway turns on whether the injury is open or closed.

• Closed central slip injury: splint the PIP joint in full extension for six to eight weeks. Leave the DIP joint free and teach active DIP flexion exercises to prevent lateral band adhesion. MCP joint movement is preserved.
• Open lacerations: refer for surgical exploration and primary repair of the central slip. RCEM Learning gives six weeks of splintage after suture repair of a divided central slip. Splinting alone is insufficient where a wound crosses the extensor mechanism.
• PIP dislocation with a positive test: treat as a central slip injury once the joint is reduced. Splint in extension and refer to hand surgery if any doubt remains about tendon integrity.
• Partial tears and equivocal tests: splint the PIP joint in extension and review at two weeks with a repeat clinical assessment.

Active DIP flexion exercises during the splinting period are critical, not optional. They stop the lateral bands adhering in their displaced volar position, which would produce a fixed boutonniere deformity even after the central slip has healed. Weekly review for the first four weeks is standard in most hand surgery units.

Set against the clock, the pathway is easier to hold in mind. Every branch below ends at a review point that falls inside the window in which the deformity would otherwise set.

How Pabau structures hand injury assessment and follow-up

Documenting the Elson test accurately matters as much as performing it. A note reading “Elson positive” tells the next reviewer almost nothing. A note reading “positive Elson test, rigid DIP extension, proximal phalanx stabilized, right index finger” tells them what was seen, how, and where.

Practice management software like Pabau replaces that free-text note with a structured hand injury assessment form. The form prompts for the posture of both joints, the technique used, the result, and the immediate plan. A free-text field sits alongside the structured ones, so the clinician can still record the detail a binary result cannot hold.

For a practice running hand therapy alongside a general caseload, that structure has to sit in the same record as the appointment. A physical therapy EMR keeps the assessment, the splint issue date, and every review appointment on one patient timeline.

Follow-up is where these injuries are lost. Pabau’s automated workflows trigger a reminder at two weeks and again at six weeks once a positive Elson test is recorded. Fewer patients drop out before healing is confirmed. If you are comparing systems for a rehab caseload, our guide to physiotherapy practice management software sets out the options.

The same records satisfy an audit. Dated review notes and structured assessments are what an inspector looks for. Our summary of physiotherapy compliance requirements covers the standards that apply to musculoskeletal practice.

Structure hand injury assessments and their follow-up

Pabau gives physical therapy, sports medicine, and orthopedic practices structured clinical forms, a single patient timeline, and automated review reminders. Assessments stay complete and patients reach the end of the splinting protocol.

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Conclusion

Central slip injuries are missed because the first presentation looks benign and no single sign is diagnostic without this test. That makes the Elson test one of the highest-yield minutes in a hand examination.

Read both joints at once, stabilize the proximal phalanx, and record what you saw rather than a verdict. Treat every equivocal result as positive. For an open dorsal wound, send the patient for exploration whatever the test shows.

Six to eight weeks in a splint costs the patient far less than a fixed boutonniere deformity costs them later. Dropout at week three is what undoes the treatment, and catching it is a scheduling problem rather than a clinical one. Book a demo to see how Pabau keeps hand injury assessments structured and review reminders automatic.

Continue your research

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Want the patient to show you where it hurts? Hand pain diagrams give you a printable chart patients can mark up before the consultation.

Responsible for compliance across a rehab practice? Physiotherapy clinic compliance requirements sets out the documentation and regulatory standards for musculoskeletal practice.

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