Acute Knee Injuries – what is the best imaging modality?

9th September 2026, NIA Diagnostic Imaging

acute knee injury

Acute knee injuries commonly occur as a result of direct blows to the joint, such as motor vehicle accidents, but can also occur after sudden twisting, instability events, or falls (4). After the injury, patients often clinically present with any or all of the following: focal or generalised knee pain, locking of the knee, joint effusion or inability to bear weight. There are multiple soft tissue or bony structures in the knee that can be injured. The severity of the injury can range from mild sprains or localised bruising to significant soft tissue (including ligament or cartilage tears) and fractures. Choosing the right imaging modality can be tricky.

Plain X-Ray

X-ray is the standard first-line imaging modality for acute knee injuries. Capable of detecting:

Fractures – patella, tibial plateau, femoral condyle
Avulsion fractures
Loose bodies within the joint
Bony malalignment
Joint effusion – indicative of further underlying pathology

The Ottawa Knee Rules help GPs identify which patients genuinely need X-ray, reducing unnecessary radiation exposure. (3)

X-ray is recommended if the patient has any of the following:

Age ≥55 years
Isolated patella tenderness
Fibula head tenderness
Inability to flex knee to 90 degrees
Inability to bear weight immediately after injury and inability to take four steps in the emergency department

If none of these criteria are met, imaging can often be safely deferred, and conservative management with follow-up review may be appropriate. If symptoms persist or worsen, imaging can be arranged at that point.

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI) is the gold standard for evaluating and diagnosing soft tissue injuries in the knee. (6)

Key roles of MRI in acute knee injuries include:

Identification of ACL, PCL, MCL and LCL tears
Detection of meniscal tears — medial and lateral
Assessment of articular cartilage damage and osteochondral lesions
Identification of bone marrow oedema and bone bruising
Detection of occult fractures not visible on x-ray

MRI also plays an important role in surgical planning and assisting clinicians by:

Guiding surgical decision-making for both soft tissue and bony pathology
Evaluating the integrity of previous reconstructions such as ACL grafts
Providing comprehensive assessment of all structures before arthroscopy
Determining whether surgical or conservative management is most appropriate

Computed Tomography (CT)

Computed Tomography (CT) is not recommended as a first-line imaging modality for most acute knee injuries.

Instead, CT serves a complementary role, sitting between plain radiography and MRI in the imaging pathway. (5)

Key indications include:

Evaluation of occult fractures not visible on initial X-ray
Characterisation of known fractures, particularly for preoperative planning
3D reconstruction for complex fracture patterns
Assessment of articular depression, fragment orientation and comminution.

Ultrasound

Despite MRI remaining the gold standard, ultrasound is gaining popularity due to its real-time imaging, accessibility, time-efficiency and safety. (5)

Key indications include:

Pathology within superficial structures — patellar and quadriceps tendons and collateral ligaments
Detection of joint effusion and haemarthrosis post-trauma; indicative of further underlying pathology

In the private setting, ultrasound remains a practical alternative for soft tissue imaging, where MRI availability and costs are barriers.

As per the Royal Australian College of General Practitioners, Clinical Imaging selection in acute knee injuries is guided by the findings of physical examination and clinical diagnosis. (5)

X-ray: first-line for trauma when indicated by clinical decision tools
MRI: gold standard for soft tissue structures and internal derangement
CT: complex fracture characterisation and surgical planning
Ultrasound: superficial soft tissue injuries or when MRI is inaccessible/contraindicated

At NIA Diagnostic Imaging, we offer all imaging modalities across three conveniently located sites. We accept urgent appointments to support timely assessment of acute knee injuries.

REFERENCES

Australian Primary Health Care Nurses Association. (2017). Acute ankle and knee injuries: Limited role for imaging. Primary Times, 17(1).
Choudhary, N., Nagar, A., Singh, S., & Lakhar Guru, B. (2025). Role of MRI in diagnosis of knee injuries: An observational study. International Journal of Medicine and Public Health, 15(1), 43–48.
Haque, T., & Yao, K. (2012). The Ottawa knee rules: A useful clinical decision tool. Australian Family Physician, 41(4), 229–231. https://www.racgp.org.au/afp/2012/april/the-ottawa-knee-rules
Queensland Health. (2024, February 13). Knee injury (acute). Queensland Government. https://www.health.qld.gov.au/cpc/orthopaedics/acute-knee-pain
Ridley, U., & Ridley, L. (2020). Imaging of the knee: Common acute presentations to general practice. Australian Journal of General Practice, 49(6). https://doi.org/10.31128/AJGP-10-19-5120
Shetty, N. D., Bora, N., & Shelar, S. S. (2024). The role of magnetic resonance imaging in the evaluation of knee pain. Cureus, 16.

PFO Closure

Furlan AJ, Reisman M, Massaro J, et al. Closure or medical therapy for cryptogenic stroke with patent foramen ovale. N Engl J Med 2012; 366: 991–

A multicenter, randomized, open-label trial of closure with a percutaneous device, as compared with medical therapy alone, in patients between 18 and 60 years of age who presented with a cryptogenic stroke or transient ischemic attack (TIA) and had a patent foramen ovale. The primary end point was a composite of stroke or transient ischemic attack during 2 years of follow-up, death from any cause during the first 30 days, or death from neurologic causes between 31 days and 2 years.

Results:

Primary end point was 5.5% in the closure group as compared with 6.8% in the medical-therapy group (adjusted hazard ratio, 0.78; 95% confidence interval, 0.45 to 1.35; P = 0.37)

Conclusion:

“In patients with cryptogenic stroke or TIA who had a patent foramen ovale, closure

with a device did not offer a greater benefit than medical therapy alone for the

prevention of recurrent stroke or TIA”

2 Saver JL, Carroll JD, Thaler DE, et al. Long-term outcomes of patent foramen ovale closure or medical therapy after stroke. N Engl J Med 2017; 377: 1022–

A multicenter, randomised, open-label trial ,randomly assigned patients 18 to 60 years of age who had a patent foramen ovale (PFO) and had had a cryptogenic ischemic stroke to undergo closure of the PFO (PFO closure group) or to receive medical therapy alone (aspirin, warfarin, clopidogrel, or aspirin combined with extended-release dipyridamole; medical-therapy group). The primary efficacy end point was a composite of recurrent nonfatal ischemic stroke, fatal ischemic stroke, or early death after randomisation.

Results:

Recurrent ischemic stroke occurred in 18 patients in the PFO closure group and in 28 patients in the medical-therapy group, resulting in rates of 0.58 events per 100 patient-years and 1.07 events per 100 patient years, respectively (hazard ratio 0.55; 0.31 – 0.999; P = 0.046)

Conclusion:

“Among adults who had had a cryptogenic ischemic stroke, closure of a PFO was associated with a lower rate of recurrent ischemic strokes than medical therapy alone during extended follow-up.”

Meier B, Kalesan B, Mattle HP, et al. Percutaneous closure of patent foramen ovale in cryptogenic embolism. N Engl J Med 2013; 368: 1083–

A prospective, multicenter, randomised, event-driven trial, randomly assigned patients to medical therapy alone (anti-platelet or warfarin therapy) or closure of the patent foramen ovale.

Results:

9 patients in the closure group and 16 in the medical-therapy group had a recurrence of stroke (hazard ratio with closure, 0.49; 0.22 – 1.11; P = 0.08). The primary analysis of the intentionto- treat cohort showed a nominal 51% hazard rate reduction with closure, but the reduction did not reach significance.

Conclusions:

” …there was no significant benefit associated with closure of a patent foramen ovale in adults who had had a cryptogenic ischaemic stroke.”

Sondergaard L, Kasner SE, Rhodes JF, et al. Patent foramen ovale closure or antiplatelet therapy for cryptogenic stroke. N Engl J Med 2017; 377: 1033–

Multinational trial involving patients with a PFO who had had a cryptogenic stroke, randomly assigned patients to undergo PFO closure plus antiplatelet therapy or to receive antiplatelet therapy alone.

Results:

During a median follow-up of 3.2 years, clinical ischemic stroke occurred in 6 of 441 patients (1.4%) in the PFO closure group and in 12 of 223 patients (5.4%) in the antiplatelet-only group (hazard ratio, 0.23; 0.09 to 0.62; P=0.002).

Conclusions:

“Among patients with a PFO who had had a cryptogenic stroke, the risk of subsequent ischemic stroke was lower among those assigned to PFO closure combined with antiplatelet therapy than among those assigned to antiplatelet therapy alone; however, PFO closure was associated with higher rates of device complications and atrial fibrillation.”

Mas JL, Derumeaux G, Guillon B, et al. Patent foramen ovale closure or anticoagulation vs. antiplatelets after stroke. N Engl J Med 2017; 377: 1011–

In a multicenter, randomised, open-label trial patients 16-60 years of age who had had a recent stroke attributed to PFO, to transcatheter PFO closure plus long-term antiplatelet therapy, antiplatelet therapy alone or oral anticoagulation.

Results:

No stroke occurred among patients in the PFO closure group, whereas stroke occurred in 14 of the 235 patients in the antiplatelet- only group (hazard ratio, 0.03; 0 to 0.26; P<0.001). Large number of patients discontinued anti-coagulation in the anti-coagulant group and statistical significance was not analysed because the study was not adequately powered to compare outcomes.

Conclusion:

“Among patients who had had a recent cryptogenic stroke attributed to PFO with an associated atrial septal aneurysm or large interatrial shunt, the rate of stroke recurrence was lower among those assigned to PFO closure combined with antiplatelet therapy than among those assigned to antiplatelet therapy alone. PFO closure was associated with an increased risk of atrial fibrillation.”

Lee PH, Song J-K, Kim JS, et al. Cryptogenic stroke and high-risk patent foramen ovale: the DEFENSE-PFO Trial. J Am Coll Cardiol 2018; 71: 2335–

Patients with cryptogenic stroke and high-risk PFO were divided between a transcatheter PFO closure and a medication-only group.

Results:

No events occurred in the PFO closure group. 12.9% of patients in the medication group had an event (p= 0.023).

Conclusion:

“PFO closure in patients with high-risk PFO characteristics resulted in a lower rate of the primary endpoint as well as stroke recurrence”