Each knee maneuver arrives with its reason, Lachman for the cruciate, McMurray and joint line for the meniscus, valgus stress for the collateral, and a probability shift per result. Searches like "nu 552 unit 3 assignment example", "nu552 unit 3 sample" and "nu552 unit 3 example" land here.
Seven Maneuvers for One Swollen Knee: An Exam Rationale With Likelihood Ratios After a Pivoting Injury
[Student Name]
Purdue University Global
NU552: Advanced Health Assessment and Diagnostic Reasoning
Unit 3 Assignment
[Instructor Name]
[Date]
The patient is a composite built for the assignment; no real patient is described.
The History That Sets the Starting Probabilities
Mr. [T.], 27, was playing in a weekend league when he planted his right foot to change direction and felt his knee give way with an audible pop. He could not continue. Within two hours the knee was visibly swollen. He saw us the next morning, walking with a limp and unable to fully straighten the knee.
A noncontact pivoting injury, a pop, rapid swelling and giving way together make an anterior cruciate ligament tear the leading hypothesis. Swelling within a few hours suggests hemarthrosis, bleeding into the joint, which usually means an injured structure with a blood supply: the anterior cruciate ligament most often, a patellar dislocation or an osteochondral fracture less often (Solomon et al., 2001). Before any maneuver, the estimates were:
1. Anterior cruciate ligament tear: [50] percent, roughly even odds.
2. Meniscal tear, often accompanying the ligament injury: [30] percent.
3. Medial collateral ligament sprain: [20] percent.
4. Patellar dislocation that relocated: [10] percent.
The estimates are not exclusive; injuries occur together.
How the Numbers Were Calculated
For each maneuver, the positive likelihood ratio is sensitivity divided by one minus specificity, and the negative likelihood ratio is one minus sensitivity divided by specificity. A probability is converted to odds, multiplied by the ratio and converted back. A ratio above 10 or below 0.1 moves an estimate a long way; a ratio between 0.5 and 2 barely moves it at all. Sensitivity and specificity come from the cited meta-analyses and are shown in brackets.
The Maneuvers
1. Lachman test. Hypothesis: anterior cruciate tear. Sensitivity [0.85], specificity [0.94] (Benjaminse et al., 2006). Positive ratio 14.2, negative ratio 0.16. Result: increased anterior translation with a soft endpoint. Change: 50 to 93 percent.
2. Anterior drawer. Hypothesis: anterior cruciate tear. Sensitivity [0.55], specificity [0.92] (Benjaminse et al., 2006). Positive ratio 6.9, negative ratio 0.49. Result: positive, limited by guarding. Change: not combined with Lachman; see below.
3. Pivot shift. Hypothesis: anterior cruciate tear. Sensitivity [0.24], specificity [0.98] (Benjaminse et al., 2006). Positive ratio 12, negative ratio 0.78. Result: deferred for guarding.
4. Valgus stress in full extension and at 30 degrees. Hypothesis: medial collateral injury, and combined injury if opening occurs in extension. No pooled estimate used. Result: pain at 30 degrees without gapping, stable in extension.
5. McMurray test. Hypothesis: meniscal tear. Sensitivity [0.70], specificity [0.71] (Hegedus et al., 2007). Positive ratio 2.4, negative ratio 0.42. Result: negative, performed with limited flexion. Change: 30 to 15 percent.
6. Medial joint line palpation. Hypothesis: meniscal tear. Sensitivity [0.63], specificity [0.77] (Hegedus et al., 2007). Positive ratio 2.7, negative ratio 0.48. Result: tender. Change: 15 to about 33 percent.
7. Patellar apprehension. Hypothesis: patellar dislocation. No pooled estimate used. Result: no apprehension, no medial patellar tenderness.
Commentary on Each Maneuver
The Lachman test was performed first, at 20 to 30 degrees of flexion, because it is the most accurate examination test for an anterior cruciate tear and because a swollen, guarded knee tolerates this position better than 90 degrees. A soft endpoint with increased translation compared with the left knee is a positive result. With a positive ratio of 14.2, it moved the estimate from even odds to about 93 percent. Had it been negative, the ratio of 0.16 would have lowered the estimate to about 14 percent, which is why the Lachman is useful for ruling out as well as ruling in.
The anterior drawer was performed at 90 degrees, as far as he would allow. It was positive, but it was not multiplied onto the Lachman result. Both tests measure the same laxity of the same ligament, so their results are not independent, and multiplying their ratios would overstate the certainty. The drawer adds confidence rather than a separate calculation. Its lower sensitivity in acute injury, when guarding and effusion prevent the hamstrings from relaxing and the knee from reaching 90 degrees, is a further reason to rely on the Lachman.
The pivot shift was deferred. It requires a relaxed patient and reproduces the giving-way event, and in an acutely swollen knee it is painful and often impossible. Deferring it cost little. It is a rule-in test with a positive ratio near 12, but its negative ratio of 0.78 means a negative result would have lowered 93 percent only to about 92 percent. It will be more useful under anesthesia or in a later examination.
The valgus stress test was performed in full extension and at 30 degrees. Opening at 30 degrees suggests an isolated medial collateral injury; opening in full extension suggests the medial collateral and a cruciate ligament or the posterior capsule are both injured. He had pain at 30 degrees without gapping, consistent with a mild medial collateral sprain, and no opening in extension. No pooled accuracy estimate was applied, because studies of this test are few and small (Malanga et al., 2003).
The meniscus tests were performed because a meniscal tear accompanies many anterior cruciate injuries. The McMurray test was negative, but flexion was limited, and its ratios are modest. The negative result lowered a 30 percent estimate to about 15 percent. Medial joint line tenderness raised it again, to about 33 percent. That sequence multiplies two ratios, which assumes the two tests are independent. They are not fully independent, since both are affected by the same effusion and the same medial collateral sprain, which can itself cause medial joint line tenderness. The meniscal estimate is therefore uncertain and best described as unresolved.
Patellar apprehension was tested because a patellar dislocation that relocated on its own can cause the same pop and rapid swelling. There was no apprehension and no tenderness along the medial patellar border, making this less likely.
Where the Examination Leaves the Hypotheses
1. Anterior cruciate tear: about 93 percent, effectively established clinically.
2. Meniscal tear: unresolved, roughly 30 percent, with the examination limited by effusion and guarding.
3. Medial collateral sprain: likely, mild, with no opening.
4. Patellar dislocation: less likely.
The examination has done most of its work for the anterior cruciate question. The meniscal question is left open. Magnetic resonance imaging is the step that would settle it, and it would also show bone bruising, an osteochondral injury or other structures the examination cannot reach, which is information the patient and a surgeon will need to plan treatment.
References
Benjaminse, A., Gokeler, A., & van der Schans, C. P. (2006). Clinical diagnosis of an anterior cruciate ligament rupture: A meta-analysis. Journal of Orthopaedic & Sports Physical Therapy, 36(5), 267-288. https://doi.org/10.2519/jospt.2006.2011
Hegedus, E. J., Cook, C., Hasselblad, V., Goode, A., & McCrory, D. C. (2007). Physical examination tests for assessing a torn meniscus in the knee: A systematic review with meta-analysis. Journal of Orthopaedic & Sports Physical Therapy, 37(9), 541-550. https://doi.org/10.2519/jospt.2007.2560
Malanga, G. A., Andrus, S., Nadler, S. F., & McLean, J. (2003). Physical examination of the knee: A review of the original test description and scientific validity of common orthopedic tests. Archives of Physical Medicine and Rehabilitation, 84(4), 592-603. https://doi.org/10.1053/apmr.2003.50026
Solomon, D. H., Simel, D. L., Bates, D. W., Katz, J. N., & Schaffer, J. L. (2001). Does this patient have a torn meniscus or ligament of the knee? Value of the physical examination. JAMA, 286(13), 1610-1620. https://doi.org/10.1001/jama.286.13.1610
How this NU552 Unit 3 example is structured
The rationale precedes every result in the text, so no maneuver appears to have been chosen after the fact. Starting probabilities are stated before the exam and justified from the history: a pop, swelling within hours and giving way put a cruciate tear at roughly even odds. Likelihood ratios are shown as calculated, with the formula given once, so any figure can be checked. The paper separates maneuvers useful for ruling in from those useful for ruling out and places each accordingly. Where two tests are combined for the meniscus, it warns that multiplying their ratios assumes an independence the tests do not fully have. Deferred maneuvers are listed with reasons. The end restates the remaining hypotheses with approximate probabilities and names imaging as the step that would settle the meniscal question the exam left open.
Get an NU552 Unit 3 example written to your instructions
Whichever joint or system your NU552 Unit 3 prompt assigns, send it with the case, any accuracy figures your instructor supplied and the rubric. Ratios come back calculated openly, each maneuver justified by the hypothesis it tests and every result tied to a probability shift, in a first rationale that is free, follows your instructions and arrives within 24-48h. The paper above is an original model document written by our desk, not a submitted student paper and not an official Purdue University Global document.
NU552 Unit 3 questions, answered
Where do the sensitivity and specificity figures come from?
From a published diagnostic accuracy study or meta-analysis, cited in the paper. Published values differ from one source to the next, so the sample puts them in brackets beside its reference. If your instructor supplies specific values or a required source, the ratios are calculated from those instead, with the working shown so any figure can be checked.
Do I have to calculate post-test probabilities?
Some sections require it; others accept likelihood ratios with a plain-language statement of their effect. The sample does both, because a stated shift from 50 to about 93 percent makes a ratio concrete. Whether your rubric asks for a nomogram, odds arithmetic or neither, the paper follows that requirement.
What if a maneuver could not be tolerated?
Record it as deferred and say why. A guarded knee often defeats the pivot shift, and pain can limit other tests. The sample treats deferral as information, notes how much the missing result would have mattered, and names when the maneuver might be repeated once the swelling settles.