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Teaching cases: special tests and likelihood ratios
Twelve short cases for teaching how a special test changes the chance of a condition. Each gives a patient, a starting chance, a question, then the answer: the test, its published figures, and what a positive or negative result does to the chance. Each case also comes as a two-page printable handout: the patient and question on the first page, the answer on the second.
The patients are invented for teaching. The starting chances are teaching assumptions, not published figures. The test figures come from the source on each test page. Written by Shane Tompson, physiotherapist (Master of Physiotherapy, Griffith University), over 20 years in clinical practice. Drafted with AI assistance.
The cases
Teaching case · Knee · invented for teaching, not a real patient
ACL rupture: the Lachman test
The patient. A 24-year-old netball player landed from a jump, felt her knee give way and heard a pop. The knee swelled within a few hours. She is seen five days later.
Starting chance. For this exercise, assume a 50% chance of ACL rupture before testing. This is a teaching assumption, not a published figure.
Question. You suspect an ACL rupture and perform the Lachman test. What would a positive or a negative result do to the chance?
Answer
The test. The knee is flexed to 20–30° with the thigh supported and the hamstrings relaxed. The examiner stabilises the femur with one hand and draws the tibia forward with the other. Positive: Greater anterior translation than in the other knee, with a soft or absent end-feel.
Why this test. The library rates this test as ‘best used to rule in’ for ACL rupture. Sensitivity 81%, specificity 85%; LR+ 5.72, LR− 0.24.
| Result | Likelihood ratio | Chance after the test |
|---|
| Positive | 5.72 | about 85% |
| Negative | 0.24 | about 19% |
Take-home point. The positive result is the useful one: it moves the chance from 50% to about 85%. A negative result brings it down to about 19%, so about 19 in 100 people like this would still have the condition; a negative does not rule it out on its own.
Figures: Sokal PA, Norris R, Maddox TW, Oldershaw RA. The diagnostic accuracy of clinical tests for anterior cruciate ligament tears are comparable but the Lachman test has been previously overestimated: a systematic review and meta-analysis. Knee Surg Sports Traumatol Arthrosc. 2022;30(10):3287–3303. They describe the patients in that study, not every patient. Worked with odds: starting odds × likelihood ratio = odds after the test.
Lachman test: full figures and source · Try other starting chances in the calculator · Red flags to screen for first · Print this case (PDF)
Teaching case · Knee · invented for teaching, not a real patient
ACL rupture: the Pivot shift test
The patient. A 30-year-old soccer player twisted his knee in a tackle three weeks ago. Since then the knee has felt as though it might give way when he turns.
Starting chance. For this exercise, assume a 50% chance of ACL rupture before testing. This is a teaching assumption, not a published figure.
Question. You plan a pivot shift test. How much would a positive result help, and how much would a negative one?
Answer
The test. The patient is relaxed and supine. From extension, the examiner internally rotates the tibia, applies a valgus force and slowly flexes the knee. Positive: A clunk as the subluxed lateral tibial plateau reduces, at around 20–40° of flexion.
Why this test. The library rates this test as ‘best used to rule in’ for ACL rupture. Sensitivity 55%, specificity 94%; LR+ 10.7, LR− 0.48.
| Result | Likelihood ratio | Chance after the test |
|---|
| Positive | 10.7 | about 91% |
| Negative | 0.48 | about 32% |
Take-home point. The positive result is the useful one: it moves the chance from 50% to about 91%. A negative result brings it down to about 32%, so about 32 in 100 people like this would still have the condition; a negative does not rule it out on its own.
Figures: Sokal PA, Norris R, Maddox TW, Oldershaw RA. The diagnostic accuracy of clinical tests for anterior cruciate ligament tears are comparable but the Lachman test has been previously overestimated: a systematic review and meta-analysis. Knee Surg Sports Traumatol Arthrosc. 2022;30(10):3287–3303. They describe the patients in that study, not every patient. Worked with odds: starting odds × likelihood ratio = odds after the test.
Pivot shift test: full figures and source · Try other starting chances in the calculator · Red flags to screen for first · Print this case (PDF)
Teaching case · Foot, ankle & calf · invented for teaching, not a real patient
Achilles tendon rupture: the Thompson (Simmonds) test
The patient. A 44-year-old man lunged for a ball at squash and felt as if someone had kicked him in the back of the heel. He can walk, but pushing off on that foot is weak.
Starting chance. For this exercise, assume a 50% chance of Achilles tendon rupture before testing. This is a teaching assumption, not a published figure.
Question. You suspect an Achilles tendon rupture. What does the Thompson test add?
Answer
The test. The patient lies prone with the feet over the end of the couch (or kneels on a chair). The examiner squeezes the calf muscle belly, observes the foot and compares sides. Positive: Absence of plantarflexion of the foot when the calf is squeezed.
Why this test. The library rates this test as ‘treat with caution’ for Achilles tendon rupture. Sensitivity 96%, specificity 93%; LR+ 13.71, LR− 0.04.
| Result | Likelihood ratio | Chance after the test |
|---|
| Positive | 13.71 | about 93% |
| Negative | 0.04 | about 4% |
Take-home point. Read the caution on the test page before relying on either result: one study at high risk of bias, with only 28 people without a rupture. On the published figures a negative brings the chance from 50% to about 4% and a positive lifts it to about 93%.
Figures: Reiman M, Burgi C, Strube E, et al. The utility of clinical measures for the diagnosis of Achilles tendon injuries: a systematic review with meta-analysis. J Athl Train. 2014;49(6):820–829. They describe the patients in that study, not every patient. Worked with odds: starting odds × likelihood ratio = odds after the test.
Thompson (Simmonds) test: full figures and source · Try other starting chances in the calculator · Red flags to screen for first · Print this case (PDF)
Teaching case · Shoulder & upper arm · invented for teaching, not a real patient
Rotator cuff tear: the Empty can / Jobe's test
The patient. A 58-year-old has had pain over the outer shoulder for three months, worse when lifting the arm overhead. There was no injury.
Starting chance. For this exercise, assume a 30% chance of rotator cuff tear before testing. This is a teaching assumption, not a published figure.
Question. You want to know whether a rotator cuff tear is likely. What does the empty can test tell you, and which result is more useful?
Answer
The test. With the arm at about 90° in the scapular plane and the thumb down, the examiner presses down at the wrist while the patient resists. Positive: Weakness compared with the other side, or pain.
Why this test. The library rates this test as ‘best used to rule out’ for rotator cuff tear. Sensitivity 88%, specificity 62%; LR+ 2.3, LR− 0.19.
| Result | Likelihood ratio | Chance after the test |
|---|
| Positive | 2.3 | about 50% |
| Negative | 0.19 | about 8% |
Take-home point. The negative result is the stronger one: it brings the chance down from 30% to about 8%. A positive result lifts it to about 50%, which is not enough to confirm the condition on its own.
Figures: Jain NB, Luz J, Higgins LD, Dong Y, Warner JJP, Matzkin E, Katz JN. The Diagnostic Accuracy of Special Tests for Rotator Cuff Tear: The ROW Cohort Study. Am J Phys Med Rehabil. 2017;96(3):176–183. They describe the patients in that study, not every patient. Worked with odds: starting odds × likelihood ratio = odds after the test.
Empty can / Jobe's test: full figures and source · Try other starting chances in the calculator · Red flags to screen for first · Print this case (PDF)
Teaching case · Shoulder & upper arm · invented for teaching, not a real patient
Rotator cuff tear: the Drop arm test
The patient. A 62-year-old has had shoulder pain and weakness lifting the arm for two months. There was no clear injury.
Starting chance. For this exercise, assume a 30% chance of rotator cuff tear before testing. This is a teaching assumption, not a published figure.
Question. The drop arm test is negative. Has that ruled out a rotator cuff tear?
Answer
The test. The examiner passively abducts the arm fully, then asks the patient to lower it slowly. Positive: The arm drops or cannot be lowered with control, usually around 90°.
Why this test. The library rates this test as ‘best used to rule in’ for rotator cuff tear. Sensitivity 24%, specificity 96%; LR+ 6.45, LR− 0.79.
| Result | Likelihood ratio | Chance after the test |
|---|
| Positive | 6.45 | about 73% |
| Negative | 0.79 | about 25% |
Take-home point. The positive result is the useful one: it moves the chance from 30% to about 73%. A negative result brings it down to about 25%, so about 25 in 100 people like this would still have the condition; a negative does not rule it out on its own.
Figures: Jain NB, Luz J, Higgins LD, Dong Y, Warner JJP, Matzkin E, Katz JN. The Diagnostic Accuracy of Special Tests for Rotator Cuff Tear: The ROW Cohort Study. Am J Phys Med Rehabil. 2017;96(3):176–183. They describe the patients in that study, not every patient. Worked with odds: starting odds × likelihood ratio = odds after the test.
Drop arm test: full figures and source · Try other starting chances in the calculator · Red flags to screen for first · Print this case (PDF)
Teaching case · Shoulder & upper arm · invented for teaching, not a real patient
Anterior instability: the Apprehension test
The patient. A 20-year-old rugby player has had pain and a sense of unease at the front of his shoulder when his arm is taken out to the side and back, since a heavy tackle six weeks ago. He is not sure whether anything moved at the time.
Starting chance. For this exercise, assume a 50% chance of anterior instability before testing. This is a teaching assumption, not a published figure.
Question. You wonder about anterior shoulder instability. What would a positive or a negative apprehension test do to the chance?
Answer
The test. With the patient supine or seated and the arm at 90° abduction and 90° elbow flexion, the examiner slowly externally rotates the shoulder. Positive: Apprehension, the feeling that the shoulder will slip; pain alone does not count.
Why this test. The library rates this test as ‘best used to rule in’ for anterior instability. Sensitivity 72%, specificity 96%; LR+ 20.2, LR− 0.29.
| Result | Likelihood ratio | Chance after the test |
|---|
| Positive | 20.2 | about 95% |
| Negative | 0.29 | about 22% |
Take-home point. The positive result is the useful one: it moves the chance from 50% to about 95%. A negative result brings it down to about 22%, so about 22 in 100 people like this would still have the condition; a negative does not rule it out on its own.
Figures: Farber AJ, Castillo R, Clough M, Bahk M, McFarland EG. Clinical assessment of three common tests for traumatic anterior shoulder instability. J Bone Joint Surg Am. 2006;88(7):1467–1474. They describe the patients in that study, not every patient. Worked with odds: starting odds × likelihood ratio = odds after the test.
Apprehension test: full figures and source · Try other starting chances in the calculator · Red flags to screen for first · Print this case (PDF)
Teaching case · Elbow & forearm · invented for teaching, not a real patient
Complete distal biceps tendon rupture: the Hook test
The patient. A 45-year-old man felt a pop at the front of his elbow while lifting a heavy box, followed by bruising in the crook of the elbow.
Starting chance. For this exercise, assume a 50% chance of complete distal biceps tendon rupture before testing. This is a teaching assumption, not a published figure.
Question. You suspect a distal biceps rupture. What does the hook test add?
Answer
The test. With the elbow at 90° and the forearm fully supinated, the examiner attempts to hook the index finger under the distal biceps tendon from the lateral side. Positive: No cord-like tendon can be hooked.
Why this test. The library rates this test as ‘best used to rule in’ for complete distal biceps tendon rupture. Sensitivity 71.4%, specificity 95.5%; LR+ 15.71, LR− 0.3.
| Result | Likelihood ratio | Chance after the test |
|---|
| Positive | 15.71 | about 94% |
| Negative | 0.3 | about 23% |
Take-home point. The positive result is the useful one: it moves the chance from 50% to about 94%. A negative result brings it down to about 23%, so about 23 in 100 people like this would still have the condition; a negative does not rule it out on its own.
Figures: Zwerus EL, van Deurzen DFP, van den Bekerom MPJ, The B, Eygendaal D. Distal Biceps Tendon Ruptures: Diagnostic Strategy Through Physical Examination. Am J Sports Med. 2022;50(14):3956–3962. They describe the patients in that study, not every patient. Worked with odds: starting odds × likelihood ratio = odds after the test.
Hook test: full figures and source · Try other starting chances in the calculator · Red flags to screen for first · Print this case (PDF)
Teaching case · Elbow & forearm · invented for teaching, not a real patient
UCL injury: the Moving valgus stress test
The patient. A 19-year-old baseball pitcher has pain on the inner side of his elbow when he throws.
Starting chance. For this exercise, assume a 50% chance of UCL injury before testing. This is a teaching assumption, not a published figure.
Question. You suspect an injury to the ulnar collateral ligament (UCL). Which result of the moving valgus stress test is more useful?
Answer
The test. With the shoulder at 90° abduction and full external rotation, the examiner applies a steady valgus force from full elbow flexion and extends the elbow briskly. Positive: Reproduction of the familiar medial pain, worst between about 120° and 70° of flexion.
Why this test. The library rates this test as ‘best used to rule out’ for UCL injury. Sensitivity 98%, specificity 75%; LR+ 3.94, LR− 0.02.
| Result | Likelihood ratio | Chance after the test |
|---|
| Positive | 3.94 | about 80% |
| Negative | 0.02 | about 2% |
Take-home point. The negative result is the stronger one: it brings the chance down from 50% to about 2%. A positive result lifts it to about 80%, which is not enough to confirm the condition on its own. Read these figures with care: one study in which every patient went on to surgery, so the figures may not apply to a general sports caseload.
Figures: Sciascia AD, Bowman EN, Camp C, et al. Clinical Utility of the Moving Valgus Stress Test and Milking Maneuver for Medial Ulnar Collateral Ligament Injuries of the Elbow. Am J Sports Med. 2026;54(8):1993–2002. They describe the patients in that study, not every patient. Worked with odds: starting odds × likelihood ratio = odds after the test.
Moving valgus stress test: full figures and source · Try other starting chances in the calculator · Red flags to screen for first · Print this case (PDF)
Teaching case · Low back & pelvis · invented for teaching, not a real patient
Nerve root involvement (disc herniation): the Slump test
The patient. A 40-year-old has had low back pain for six weeks, with pain spreading down the back of one leg to below the knee.
Starting chance. For this exercise, assume a 40% chance of nerve root involvement (disc herniation) before testing. This is a teaching assumption, not a published figure.
Question. You want to know whether a lumbar disc herniation is likely. What does the slump test add?
Answer
The test. With the patient seated at the edge of the couch, the trunk is slumped, the neck flexed, the knee straightened and then the ankle dorsiflexed, with symptoms checked at each step. Finally, the neck flexion is released. Positive: Reproduction of the patient's leg symptoms, which ease when the neck is released.
Why this test. The library rates this test as ‘treat with caution’ for nerve root involvement (disc herniation). Sensitivity 84%, specificity 83%; LR+ 4.9, LR− 0.19.
| Result | Likelihood ratio | Chance after the test |
|---|
| Positive | 4.9 | about 77% |
| Negative | 0.19 | about 11% |
Take-home point. Read the caution on the test page before relying on either result: case–control study (38 patients with a disc herniation on MRI against 37 with no disc bulge), which tends to overestimate accuracy. On the published figures a negative brings the chance from 40% to about 11% and a positive lifts it to about 77%.
Figures: Majlesi J, Togay H, Unalan H, Toprak S. The sensitivity and specificity of the Slump and the Straight Leg Raising tests in patients with lumbar disc herniation. J Clin Rheumatol. 2008;14(2):87–91. They describe the patients in that study, not every patient. Worked with odds: starting odds × likelihood ratio = odds after the test.
Slump test: full figures and source · Try other starting chances in the calculator · Red flags to screen for first · Print this case (PDF)
Teaching case · Low back & pelvis · invented for teaching, not a real patient
Sacroiliac joint pain: the Thigh thrust (P4) test
The patient. A 45-year-old has had persistent pain in one buttock, below the belt line, for six months. She points to the back of the pelvis as the worst spot.
Starting chance. For this exercise, assume a 25% chance of sacroiliac joint pain before testing. This is a teaching assumption, not a published figure.
Question. Could the sacroiliac joint be the source? What does the thigh thrust test tell you?
Answer
The test. The patient lies supine with the hip flexed to about 90° and the knee relaxed. The examiner places one hand under the sacrum and applies a steady posterior force along the line of the femur. Positive: Reproduction of the patient's familiar buttock or posterior pelvic pain.
Why this test. The library rates this test as ‘best used to rule out’ for sacroiliac joint pain. Sensitivity 88%, specificity 69%; LR+ 2.8, LR− 0.18.
| Result | Likelihood ratio | Chance after the test |
|---|
| Positive | 2.8 | about 48% |
| Negative | 0.18 | about 6% |
Take-home point. The negative result is the stronger one: it brings the chance down from 25% to about 6%. A positive result lifts it to about 48%, which is not enough to confirm the condition on its own.
Figures: Laslett M, Aprill CN, McDonald B, Young SB. Diagnosis of sacroiliac joint pain: validity of individual provocation tests and composites of tests. Man Ther. 2005;10(3):207–218. They describe the patients in that study, not every patient. Worked with odds: starting odds × likelihood ratio = odds after the test.
Thigh thrust (P4) test: full figures and source · Try other starting chances in the calculator · Red flags to screen for first · Print this case (PDF)
Teaching case · Hip, groin & thigh · invented for teaching, not a real patient
Ischiofemoral impingement: the Long stride walking test
The patient. A 38-year-old runner has had deep pain in one buttock for several months, worse with running, and has been referred to a hip clinic.
Starting chance. For this exercise, assume a 20% chance of ischiofemoral impingement before testing. This is a teaching assumption, not a published figure.
Question. Ischiofemoral impingement is one possibility. What does the long stride walking test add?
Answer
The test. The patient walks with deliberately long strides, then with short strides. Positive: Deep buttock or posterior hip pain at the end of hip extension during long strides, which settles with short strides.
Why this test. The library rates this test as ‘useful in both directions’ for ischiofemoral impingement. Sensitivity 94%, specificity 85%; LR+ 6.12, LR− 0.07.
| Result | Likelihood ratio | Chance after the test |
|---|
| Positive | 6.12 | about 60% |
| Negative | 0.07 | about 2% |
Take-home point. Both results help: a positive moves the chance from 20% to about 60%, and a negative brings it down to about 2%.
Figures: Gómez-Hoyos J, Martin RL, Schröder R, Palmer IJ, Martin HD. Accuracy of 2 Clinical Tests for Ischiofemoral Impingement in Patients With Posterior Hip Pain and Endoscopically Confirmed Diagnosis. Arthroscopy. 2016;32(7):1279–1284. They describe the patients in that study, not every patient. Worked with odds: starting odds × likelihood ratio = odds after the test.
Long stride walking test: full figures and source · Try other starting chances in the calculator · Red flags to screen for first · Print this case (PDF)
Teaching case · Hip, groin & thigh · invented for teaching, not a real patient
Sciatic nerve entrapment in the buttock: the Seated piriformis stretch test
The patient. A 50-year-old has had deep buttock pain for four months, with pain down the back of the thigh, worse with sitting. Examination of the low back has not reproduced the pain.
Starting chance. For this exercise, assume a 20% chance of sciatic nerve entrapment in the buttock before testing. This is a teaching assumption, not a published figure.
Question. You wonder whether the sciatic nerve is trapped in the buttock. What does the seated piriformis stretch test add?
Answer
The test. The patient is seated with the hip at 90°. The examiner extends the knee, then moves the hip into adduction and internal rotation while palpating at the greater sciatic notch. Positive: Reproduction of the familiar buttock pain at the palpating fingers.
Why this test. The library rates this test as ‘best used to rule in’ for sciatic nerve entrapment in the buttock. Sensitivity 52%, specificity 90%; LR+ 5.22, LR− 0.53.
| Result | Likelihood ratio | Chance after the test |
|---|
| Positive | 5.22 | about 57% |
| Negative | 0.53 | about 12% |
Take-home point. The positive result is the useful one: it moves the chance from 20% to about 57%. A negative result brings it down to about 12%, so about 12 in 100 people like this would still have the condition; a negative does not rule it out on its own.
Figures: Martin HD, Kivlan BR, Palmer IJ, Martin RL. Diagnostic accuracy of clinical tests for sciatic nerve entrapment in the gluteal region. Knee Surg Sports Traumatol Arthrosc. 2014;22(4):882–888. They describe the patients in that study, not every patient. Worked with odds: starting odds × likelihood ratio = odds after the test.
Seated piriformis stretch test: full figures and source · Try other starting chances in the calculator · Red flags to screen for first · Print this case (PDF)
