Knee Dislocation and Nerve Injuries – What You Should Know

A knee dislocation is a rare but serious injury in which the bones of the knee joint lose their normal alignment. This often happens after a strong force, such as in sports accidents, traffic collisions, or falls from height. In addition to injuries to ligaments and blood vessels, the nerves running close to the joint can also be affected.

Why Nerve Injuries Are Important

Nerve injuries around the knee can lead to weakness, sensory disturbances, or movement restrictions in the lower leg and foot. These symptoms can last for varying periods of time. Early assessment helps identify any nerve involvement and decide on the most appropriate treatment steps.

Nerves at Risk in Knee Dislocation

Common peroneal nerve (nervus peroneus communis) – This nerve branches from the sciatic nerve and runs along the outside of the knee toward the lower leg. Because it passes a fixed bony structure (the fibular head) in a relatively rigid position, it has limited ability to move out of the way. In knee injuries or dislocations, it can be stretched or compressed, increasing the risk of functional impairment.

Tibial nerve (nervus tibialis) – Also a branch of the sciatic nerve, running behind the knee joint. It can be injured in more severe displacement or when there is significant swelling and bleeding.

Possible Symptoms of Nerve Damage

Weakness in lifting the foot (foot drop) – walking may feel unstable, and the foot may drag
Numbness or tingling on the top of the foot or outer lower leg
Weakness in toe extension or reduced ankle stability
Sensory loss in the sole of the foot (tibial nerve involvement)
Sometimes pain or burning sensations

Cartoon-style illustration of a person with crutches after knee dislocation and foot drop in equinus position. — Knee dislocation with typical foot drop – the foot hangs in equinus position, making walking difficult.

Diagnostics

A careful diagnostic approach is essential to assess the extent of the injury and plan treatment.

1. Clinical Examination

The function and sensitivity of the lower leg and foot are tested. This includes checking muscle strength, joint mobility, and sensation in different areas.

2. Imaging for Bone and Vascular Injuries

X-rays and MRI scans of the knee can detect fractures and soft tissue injuries. Vascular imaging (e.g., ultrasound or CT angiography) may be used if blood vessel injury is suspected.

3. Nerve Ultrasound (High-Resolution Neurosonography)

With high-resolution ultrasound, the common peroneal nerve, the tibial nerve, and the sciatic nerve in the knee region can often be visualized continuously. This allows detection of injuries, narrowing, swelling, or scar formation. Overstretch injuries are particularly important to identify, as they influence prognosis and treatment planning.

Illustration of a high-resolution ultrasound probe for visualizing peripheral nerves. — High-resolution probes can help visualize fine nerve structures in detail.

4. Nerve Conduction Studies (Neurography)

These tests measure how quickly electrical signals travel along the nerve. They are often performed 2–3 weeks after injury, when nerve changes become more detectable. Swelling or wounds in the examination area may make the procedure more challenging. In case of confirmed nerve damage, this method often cannot pinpoint the exact injury site.

llustration of the electrodes used for nerve conduction studies (neurography / NCS / ENG). — Nerve conduction studies (neurography) are performed using a stimulation electrode and adhesive skin electrodes.

5. Electromyography (EMG)

EMG assesses the electrical activity of muscles supplied by the affected nerves. After around 3 weeks, signs of denervation (loss of nerve supply) may be visible, which can indicate severe nerve injury.

Close-up of the tip of a concentric needle electrode with inner and outer recording surfaces. — The tip of the concentric needle electrode contains an inner and an outer electrode that record electrical activity of individual muscle fibers within a few millimeters.

6. MR Neurography

This specialized MRI technique can visualize nerve structures also around the knee. Image quality may be reduced in the presence of metal plates or screws used to stabilize fractures.

MRI scanner for visualizing nerve structures and soft tissues – modern imaging for diagnosing nerve damage. — MRI delivers high-resolution images of soft tissues, whereas MR neurography is specifically designed for detailed nerve imaging and diagnosis.

Treatment Approaches

Treatment options depend on the exact injury pattern, the results of diagnostic testing, and the overall health of the patient. The medical specialist can discuss possible options after the necessary examinations.

Summary

In knee dislocations, it is important to assess not only ligament and vascular injuries but also possible nerve damage. A combination of clinical examination, imaging, and neurophysiological testing can provide a detailed picture of the injury. Identifying nerve involvement early can help guide treatment and support recovery.

Disclaimer: The information provided on this page is for general informational purposes only and does not constitute medical advice. It is not a substitute for personal consultation, examination, or treatment by a physician or other qualified healthcare professional. No guarantees of healing or cure are made. While we strive for accuracy and completeness, we cannot guarantee that all content is up to date or free from errors, and we accept no liability for any inaccuracies.