A pinched nerve in the calf can cause pain in the lower leg or foot, especially when imaging is normal. How do we diagnose a pinched nerve in the lower leg, and how do we treat it?  

Common pinched nerves in calf 

Common nerves that can become damaged and cause nerve pain in the lower leg include the following:

Common peroneal nerve entrapment 

superficial nerve entrapment

Common peroneal nerve entrapment occurs when the common peroneal nerve is compressed or irritated, leading to pain, weakness, and sensory disturbances in the lower leg and foot. The most common site of entrapment is around the fibular neck, where the nerve is superficial and vulnerable to compression from external pressure, trauma, or repetitive stress. Ankle sprains can lead to nerve tethering in the lateral knee. 

Ususally, athletes complain of pain in the lateral knee, radiating into the outer calf or upper lateral thigh, near the neck of the fibula. In more severe cases, numbness, tingling, and weakness of the lower leg can occur. Pain is usually brought on by running and worsens as the athlete continues to run. When the athlete stops running, the pain will usually settle quickly, within minutes to hours. 

Superficial Peroneal Nerve Entrapment 

The superficial peroneal nerve comes from the common peroneal nerve as it wraps around the fibular head close to the outside of the knee. This nerve passes through the muscles of the outside of the leg. Then, halfway down the lower leg, it pierces the deep fascia to travel just under the skin. It is here that pinching can occur.  

Generally, common symptoms of a pinched superficial peroneal nerve include running pain in the outer part of the lower leg and the top of the foot. Sometimes, people can also experience numbness and tingling in this area. The pain is ‘switched off’ almost immediately by stopping activity. 

Usually, ankle sprains or direct trauma to the outside of the lower leg can pinch or thicken the nerve as it passes through the deep fascia.

Tarsal tunnel syndrome

tarsal tunnel syndrome

The tarsal tunnel is a space between the long bone called the tibia and the inside of the Achilles tendon. It is covered by a thick retinaculum and contains the posterior tibial nerve, vessels, and tendons.  

Tarsal tunnel syndrome occurs when the posterior tibial nerve is compressed in the tarsal tunnel, similar to carpal tunnel syndrome in the wrist.

Generally, symptoms of tarsal tunnel syndrome include burning or shooting pain in the inside of the ankle and mid-arch. Sometimes, numbness or tingling sensations can occur in the inside arch.

Compression causes include a ganglion cyst, arthritis spurs, extra muscles in the inside ankle, or twisting of the ankle.

Trapping of one branch of the tibial nerve near the heel can cause pain in the heel, often mistaken for plantar fasciitis. This condition is called Baxter’s nerve.

Sural nerve entrapment  

The sural nerve comes from the large sciatic nerve at the back of the knee. It pierces the deep fascia and travels just under the skin as it passes toward the mid-calf. It then follows the outer part of the Achilles tendon down the calf. Finally, just above the ankle, it separates from the outer part of the tendon and travels to the outer aspect of the foot.

Generally, sural nerve entrapment produces pain down the outer calf and into the outside of the ankle and foot. Sometimes, pain can be accompanied by numbness and tingling sensations. 

The sural nerve can be pinched as it passes through the deep fascia from direct trauma or ankle pain. Additionally, trapping can occur near the Achilles tendon due to Achilles tendonitis or paratendonitis. Sometimes, nerves are trapped by scar tissue or suture material after Achilles tendon repair. See this blog for further information on sural nerve pain. 

Medial plantar nerve entrapment 

The posterior tibial nerve splits at the inside part of the ankle to form the medial and lateral plantar nerves. The medial plantar nerve passes inside the medial arch close to the foot’s tendons. At one point, known as the Knott of Henry, the nerve can become trapped, causing pinpoint pain in the inner arch. Generally, this condition is referred to as jogger’s foot and is often misdiagnosed as plantar fasciitis.

How to diagnose a pinched nerve in the calf? 

It is challenging to diagnose, as symptoms often overlap with those of other conditions. In addition, we should suspect a trapped nerve in the calf when imaging, such as an MRI, is normal. 

Usually, the site of symptoms can give a clue as to which nerve is pinched. Additionally, pain from a pinched calf nerve often differs from the pain associated with tendons or joints. For example, pain from a trapped nerve is activated by walking or running and deactivated by rest. Finally, tapping the nerve at the trapping site (Tinel’s sign) may produce the symptoms.

In general, tests that are used to confirm a diagnosis include:

  • Nerve conduction studies to prove how and why entrapment has occurred. Sometimes, however, these studies may be normal in entrapment.
  • MRI scan 
  • Blood tests should be ordered to rule out other potential causes of nerve dysfunction, such as nerve inflammation associated with diabetes, an underactive thyroid, or an autoimmune disorder.

Recently, more doctors have been using ultrasound to track the nerve’s course and identify any potential points of entrapment. Ultrasound also allows for the injection of the nerve with a local anaesthetic or cortisone. However, improvement in pain after a cortisone injection makes nerve entrapment more likely.

It is essential to exclude other conditions that overlap with a trapped nerve, such as an inflamed nerve from medical diseases, local inflammation from muscles and tendons, and nerve trapping from above (sciatica or piriformis syndrome).

Does tarsal tunnel syndrome show on an MRI? 

Sometimes, if the nerve is trapped due to growth, an MRI can detect pressure on the nerve. However, MRIs do not always detect all cases of tarsal tunnel syndrome.

Treatments for nerve pain in lower leg

Once the diagnosis is confirmed, simple treatments are started.

Ibuprofen cream or tablets can reduce nerve inflammation and improve symptoms. Additionally, physical therapy techniques such as soft tissue massage, acupuncture, and neural glides can help loosen the nerve. Sometimes, medications such as amitriptyline or duloxetine can reduce nerve symptoms.

Sometimes, we use an ultrasound-guided cortisone injection at the site of a pinched nerve to confirm and help with the problem.

Finally, surgery to release the pinched nerve can be considered. However, surgery should only be considered when other treatments have been tried, and imaging or injection has confirmed the cause.

Final word from Sportdoctorlondon about a pinched nerve in the calf

Unexplained calf, foot, or ankle pain might be due to nerve damage. If imaging tests, such as X-rays or MRIs, are normal, consider a pinched nerve as a possible cause. The diagnosis is made by combining an assessment with other tests such as ultrasound, nerve conduction studies, and an injection. Overall, it is recommended to consult a doctor with experience in identifying these uncommon causes of unexplained pain.

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