Unit 1 – Anterior Cruciate Ligament Tear (Free Preview)

A Problem-Solving Approach to History Taking and Physical Examination

The learning material in this unit is designed to improve your skills in history taking and physical examination. The material includes examples of clinical findings and their analysis using a problem-solving approach. As you read through the material and watch the videos, you are encouraged to identify whether all the required elements of history taking and physical examination have been adequately covered.

Taking the Patient’s History

When taking the patient’s history, the practitioner needs to obtain sufficient information to cover the following essential elements:

• Who is the patient?
• Where is the pain?
• When was the onset?
• What caused the onset?
• What are the pain characteristics?
• What are the aggravating and relieving factors?
• What has been the course of the pain?
• Are there any associated symptoms?
• Is there a past history that is relevant to the current complaint?
• Are there any “red flags”?
• What is the list of possible causes for the patient’s complaint?

Who is the patient and where is the pain?

When was the onset and what caused the onset?

A 22-year-old female soccer player presents with right knee pain and swelling. She says that she hurt her knee the previous afternoon at soccer training. She had to stop training because of the pain and the feeling of instability, with the knee ‘giving out’ when she tried to walk on it.

Analysis: This is an acute condition with a sudden onset of pain and swelling. It has occurred in an athletic activity so a mechanical cause is most likely. The reference to instability and her description of the knee ‘giving out’ would be best explained by a ligamentous injury.

When asked about the incident, she says that she was practicing an offensive play by dribbling the ball towards the goal when she changed direction abruptly to avoid a defender. She says that she planted her right foot and then changed direction to the left. She immediately felt her right knee ‘buckle’ and a sensation of something ‘giving’ in her knee.

Analysis: The causative incident described by the patient is typical of a non-contact mechanism of anterior cruciate ligament injury. It could also correlate with a medial collateral ligament (medial compartment) injury or a patella dislocation that spontaneously relocated.

She says that she felt immediate pain deep in the knee but it is now more generalized.

Analysis: The location of the pain can be helpful in localizing the involved structure or structures.

Anterior pain can suggest the involvement of the extensor apparatus, patellofemoral disorders or injury to the attachment of the anterior cruciate ligament.

Pain in the medial region can suggest Pes Anserine bursitis, medial collateral ligament injury, medial meniscus damage, the involvement of the long hip adductors and medial knee flexors. It could also be due to referred pain from a myofascial pain syndrome such as one involving vastus medialis.

Pain felt deep in the joint could indicate internal joint derangement or, in an older patient with a chronic involvement, osteoarthritis.

This patient has described a sudden onset of pain deep in the joint that is now more generalized. Deep pain, together with her description of the buckling of the knee and something ‘giving’ at the time of the injury, strongly implicate injury to the internal restraints including the cruciate ligaments.

What are the pain characteristics?

What are the aggravating and relieving factors?

What has been the course of the pain?

She says that her knee was mildly swollen when she went to bed last night but that this has worsened overnight and resulted in significant stiffness in the joint. The pain has also worsened.

Analysis: Swelling in the presence of joint stiffness strongly suggests an internal injury to the knee. The rate of onset of swelling can help to indicate the extent of damage.

Swelling due to hemarthrosis in association with ligament ruptures or articular surface fractures arises rapidly, usually in no more than a few hours.

Swelling due to traumatic synovitis, in the absence of hemarthrosis, usually takes about 24 hours to reach full extent.

Swelling due to inflammatory arthritic conditions or septic arthritis will typically occur over a period of several days or weeks.

Other causes of local swelling in the knee region include the following:

• Swelling below the knee could be associated with acute tendonitis involving the patella tendon at its attachment to the tibial tuberosity.

• Swelling in front of the patella would suggest prepatellar bursitis.

• Swelling over the upper medial tibia suggests Pes Anserine bursitis.

• An enlargement, confined to the posterior aspect, suggests a Baker’s cyst.

Are there any associated symptoms?

When asked if she has pain in any other region she says that she also has an aching lower back. She mentions, however, that she is about to begin menstruation and that this pain is typical for her at this stage of the cycle. She says that her low back pain was present prior to her knee injury.

Analysis: There is evidence that hormonal levels at various stages of the menstrual cycle lead to an increased risk of ligament injury as higher levels of estrogen are reported to reduce the strength of collagenous materials. Elevated relaxin causes loss of tensile stiffness, leading to both weakness and instability in ligamentous restraints.

Is there a past history that is relevant to the current complaint?

She says that she has never injured her knee before.

Analysis:  This further confirms that this is a new and acute injury.

Are there any “red flags”?

The patient is asked the following questions in order to identify any “red flags” that could indicate serious pathology. Even if the patient has already provided information in the case history that relates to these questions, it is recommended that they are readdressed to ensure a thorough exploration.

Do your symptoms disappear even for a short time? “It feels much better when I am resting the leg.”
Does the pain wake you up at night? “It is uncomfortable so I’m aware of it.”
Have you recently experienced any fever, chills or night sweats? “No”.
Have you recently had any knee surgery or knee injection? “No.”
Have you recently had an infection or other illness? “No.”
Do you have a history of cancer? “No.”
Have you lost any weight recently? “No.”

Analysis: None of the patient’s responses raise a “red flag”.

What is the list of possible causes for the patient’s complaint?

Based on the available history, the initial list of possible causes for the patient’s complaint includes:

• Tendinopathy

• Ligament injury with joint instability

• Meniscal injury with joint derangement

• Bursitis

• Patellofemoral disorders

• Inflammatory arthritis

• Referral from myofascial trigger points

Reflection Point

Please stop and take a moment to consider whether the main requirements of an adequate and relevant patient history taking have been fulfilled. Are there any additional questions you would have asked and, if so, why?

Before the physical examination findings are presented below, please reflect on what physical examination procedures you would perform to adequately evaluate this patient.

Performing Physical Examination

In the sections below, you are provided with examples of physical examination findings for this patient. The material presents a systematic approach to performing a focused and relevant physical examination in order to narrow down the possible causes for the patient’s complaint. The material also provides ongoing clinical reasoning and analysis of the findings. As you read the following material, you are encouraged to identify whether the essential elements of physical examination have been adequately covered.

Vital Signs

Her vital signs are within normal limits.

Analysis: It is always important to examine the patient’s vital signs to screen for general health and identify any underlying conditions such as an infection.

Inspection

The patient appears to be in good health with a slender, athletic build. She walks with a limp and significant discomfort, limiting the time spent on the involved limb.

Analysis: The patient’s slender (ectomorphic) build is more commonly associated with a generalized increase in joint laxity than other body types. It is believed that generalized laxity increases the risk of ligament injury.

A limp characterized by less time spent on the involved side is classified as an antalgic gait and simply indicates a painful limb.

The knee is inspected in a supine position and found to be moderately swollen and slightly flexed in the resting position. She says it is uncomfortable to lay down with the knee unsupported.

Analysis:  Generalized swelling points to an involvement of the joint capsule with traumatic synovitis, most likely resulting from an intrinsic ligament injury. The slightly flexed position is explained by the increased pressure within the joint, limiting full extension.

Range of Motion

She has limitation to the range of flexion and extension of the involved knee when performed actively and passively. There is no crepitation, joint locking or ‘clunking’ but the patient complains of stiffness and discomfort throughout.

Analysis: Limitation to both active and passive flexion and extension are expected due to swelling and increased intra-articular pressure. Absence of joint locking or clunking helps to exclude meniscal injury.

Palpation

Palpation reveals some tenderness along the anterior joint line. The prepatellar and pes anserine regions are both non-tender and the muscles above and below the knee appear to have normal tone. Palpation of the quadriceps and gastrocnemius reveals a number of slight tender points, but no nodularity or pain referral.

Analysis:  The lack of significant tenderness around the knee reduces the likelihood of tendinopathy, bursitis or injury to those ligaments accessible by palpation.

There appears to be little evidence of muscle injury or myofascial trigger points in the knee region.

The knee feels warm to the touch. Pressure applied to either side of the patella and attempts to palpate the posterior aspect of the knee, reveal swelling that limits the exploration of deeper structures. Pressure applied to the patella is tolerated and reveals a spongy sensation indicative of posterior patella effusion. The Patellar Ballottement test is performed and is found to be positive. There is no tenderness at the superior or inferior poles of the patella or at the tibial tuberosity. The medial and lateral borders of the patella are also non-tender.

Analysis:  The warmth, joint swelling and posterior patella effusion revealed by palpation and pressure help confirm the presence of generalized joint inflammation. The positive Patellar Ballottement test provides further confirmation (please watch the video below if you wish to review how the Patellar Ballottement test is performed). 

The lack of tenderness at the superior and inferior poles of the patella and at the tibial tuberosity help to eliminate the involvement of the quadriceps apparatus.

The absence of tenderness along the medial border of the patella reduces the likelihood that there has been a patella dislocation. This is because lateral displacement of the patella is most typical and results in tearing of the aponeurosis of the medial quadriceps and the medial patellofemoral ligament.

Reflection Point

Given the patient’s history and examination findings up until this point, please stop and take a moment to consider which special tests should be performed to further evaluate this patient.

Special Tests

The Anterior and Posterior Drawer tests are performed and are found to be negative. A posterior sag sign is not apparent.

Analysis: In acute injuries, as in this patient, the swelling and increased joint tension, together with guarding by the hamstrings, reduce the sensitivity of the ‘drawer’ tests. They are much more accurate when assessing chronic injuries. In addition, the swelling present would make it difficult to detect a posterior sag sign. Please watch the videos below if you wish to view how these tests are performed.

Lachman’s test is performed and is found to be positive with approximately 5mm of greater displacement found on the right side in comparison with the left.

Analysis:  The Lachman’s test is considered to be highly accurate when assessing the acutely injured knee. The finding in this case, suggests a mild to moderate severity due to a partial tear of the anterior cruciate ligament. Please watch the video below if you wish to view how the Lachman’s test is performed.

The lateral pivot shift test is performed and is found to be negative.

Analysis:  In this patient this test is found to be negative. However, like the anterior drawer test, it lacks sensitivity in the acutely swollen knee, which improves in the chronic condition.

When this test is positive, it is highly indicative of an anterior cruciate ligament injury (whether acute or chronic). Please watch the video below if you wish to view how the Lateral Pivot Shift test is performed.

The Valgus and Varus Stress tests are performed and are both found to be negative.

Analysis:  The Valgus and Varus Stress tests are also prone to a lack of sensitivity in the acutely swollen knee. Therefore, even with negative results for Valgus and Varus stress tests, the integrity of the collateral ligaments is unclear. In addition, the mechanism of injury described earlier in this case presentation and the presence of tenderness along the medial joint line means that damage to the medial collateral ligament cannot be ruled out. Please watch the videos below if you wish to view how these tests are performed.

The description of the mechanism of injury, together with the patient’s report that something ‘gave way’ in the knee at the time of the incident and that instability followed, along with a positive Lachman’s test all suggest an acute anterior cruciate ligament tear as the main injury sustained by this patient.

Reflection Point

Please stop and take a moment to consider whether all the elements of an adequate and relevant physical examination have been completed for this patient. Are there any additional procedures you would have performed and, if so, why?

Imaging

The patient is referred for an MRI scan which demonstrates that most of the fibers of the anterior cruciate ligament are intact. This finding is consistent with a low grade (partial) tear.

Diagnosis

Partial tear of the anterior cruciate ligament.

Discussion

Anterior cruciate ligament (ACL) injuries are caused by contact and non-contact mechanisms, with the latter occurring in the highest frequency at around 70%. A common mechanism for a non-contact ACL injury is one in which the foot is planted on the ground with the knee in near full extension, followed by a sudden deceleration and change in direction, as would occur if the athlete dodges to the inside. As the athlete’s center of gravity remains behind and to the inside of the supporting leg the result is a ‘valgus collapse’.

ACL ruptures are commonly accompanied by hemarthrosis evidenced by a rapid and substantial swelling of the joint. In contrast, injury to the posterior cruciate and the collateral ligaments often presents without swelling.

Typically, athletes who sustain an ACL injury are unable to continue playing. In a posterior cruciate ligament injury, on the other hand, the athlete is often able to play on.

In clinical practice ACL injuries are seen most often in males, however, the number of females presenting with this injury is on the rise. This is most likely due to an increase in participation by females in formerly male-dominated sports such as soccer. On the other hand, female athletes are more prone to these injuries than their male counterparts, with an incidence that is around 5 times greater. Several explanations have been offered for the increased incidence in females which include:

• A greater occurrence of general ligamentous laxity
• Influence of hormones such as estrogen and relaxing
• A larger natural genu valgum
• Greater flexibility of the hamstrings
• Higher incidence of foot pronation (which in turn contributes to tibial medial translation)
• A smaller intercondylar notch resulting in a reduced thickness (and therefore strength) of the ligament

Manual testing procedures are hampered by swelling, the associated tension within the joint and by muscle hypertonicity or ‘guarding’. If the tests are performed immediately following the injury (prior to the onset of swelling) they are more likely to detect an injury. The usefulness of testing procedures also improves following the subsidence of swelling and even further with chronicity. Lachman’s test is an exception and is considered the most accurate even in a swollen knee. An MRI scan is also a valuable testing procedure, especially in detecting complete ACL tears, however, arthroscopy is considered to be the gold standard for diagnosis.

Injury to the anterior cruciate ligament is the most common ligament injury that subsequently requires surgery. Anterior cruciate ligament tears also greatly increase the risk of developing osteoarthritis, particularly when the ACL injury is accompanied by meniscal damage.

References and Suggested Further Readings:

Friedberg R. Anterior cruciate ligament injury. www.uptodate.com

Ireland L.  The female ACL: why is it more prone to injury? Orthop Clin North Am. 2002;33(4):63

David Zbrojkiewicz D, Vertullo C, Grayson J. Increasing rates of anterior cruciate ligament reconstruction in young Australians, 2000–2015. Med J Aust 2018; 208 (8): 354-358.

Lee K et al. Anterior cruciate ligament tears: MR imaging compared with arthroscopy and clinical tests. Radiology. 1988;166(3):861. 

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