Lateral plantar nerve entrapment causes pain on the inside of the ankle and heel. It is caused by compression of the Lateral plantar nerve. Treatment involves rest, reducing pain and inflammation, identifying, and correcting the underlying cause of the injury.
On this page:
- Symptoms & diagnosis
- Causes & anatomy
Lateral plantar nerve entrapment symptoms
Lateral plantar nerve entrapment is similar symptoms to Plantar fasciitis and Tarsal tunnel syndrome. Symptoms include pain originating from the lateral plantar nerve which radiates into the lower inside area of the heel as well as the inner ankle. Pressing in on (palpating) along the inside of foot and ankle, especially along the Abdutor hallucis muscle or the Plantar fascia where they attach to the heel bone is likely to reproduce symptoms. Sometimes pain may radiate into the middle three toes.
Numbness in the heel is not normally a symptom plantar nerve entrapment. A sports injury profession may use tinels test (play video) to help diagnose nerve entrapments. This involves tapping the nerve just behind the medial malleolus (the bony bit on the inside of the ankle) with a rubber hammer. If this triggers pain or tingling in the foot then the test is positive. However Tinel's sign is not normally present in the case of Lateral plantar nerve entrapment, whereas Tinel's test will be positive for Tarsal tunnel syndrome.
A doctor may inject the area with local anesthetic to help with diagnosis. If pain is temporarily eliminated because of the pain killing injection then this is a good indication that the lateral plantar nerve is causing the problem. Nerve conduction tests may also be used to help diagnose a plantar nerve entrapment.
Causes and anatomy
The plantar nerve branches off the posterior tibial nerve after it has passed through a passage called the tarsal tunnel, just below the medial malleolus (bony bit on the inside of the ankle). It branches into two parts called the medial plantar nerve (medial meaning inside) and the lateral plantar nerve (lateral meaning outside). The lateral plantar nerve passes down the inside of the heel and under the foot to 'innervate' the outside two toes. The medial plantar nerve splits off to innervate the middle three toes.
The lateral plantar nerve can become trapped or compressed between the abductor hallucis muscle and the quadratus planus muscle along the inside of the foot causing pain. Patients who overpronate, where the foot rolls in too much and flattens during walking or running are more susceptible to lateral plantar nerve entrapment because of the additional pressure appllied to the inside of the foot when running.
Treatment of lateral plantar nerve entrapment
Rest and avoid using the foot as much as possible as continuing to walk or train will not allow the injury to recover. Apply ice or cold therapy to help with pain and inflammation. If the injury is minor then adjusting training methods by reducing running mileage or substituting swimming or cycling for running until the injury has healed may be enough. For a more severe injury, complete rest may be advised. A doctor may prescribe anti-inflammatory medication or NSAID's (e.g. ibuprofen). Always check with a doctor before taking medication. Do not take ibuprofen if you have asthma.
To help rest the foot, the arch of the foot can be supported with a simple arch taping technique (play video). Arch taping is an excellent way of relieving symptoms and can often work instantly, although it will only last for a few hours or so, depending on how much you are on your foot and bodyweight as the tape itself starts to stretch and give slightly. It may need to be applied regularly until symptoms resolve but many people notice an immediate improvement.
Various techniques can be used to tape the foot but they all work in a very similar way by applying strips of non stretch zinc oxide sports tape under the foot to support the plantar fascia (foot arch).
Orthotics may also be prescribed to correct biomechanical problems of the foot such as overpronation. These are shaped insoles and are worn inside shoes all the time, not just when playing sport! Depending on the type of correction needed, and the depth of your pockets these can either be bought 'off the shelf' in specialist shops and pharmacies, or they can be bespoke made by a qualified sports injury professional or Podiatrist. Seek professional advice if you are not sure.
A corticosteroid injection may be administered if conservative treatment is unsuccessful. Corticosteroids are anti-inflammatory drugs which can be either injected locally or taken orally. Injected corticosteroids are more commonly used in musculoskeletal conditions, due to the maximal concentration at the site of injury and the reduced risk of side-effects. Corticosteroid injections do have a reputation of being painful, however, this can be limited with the use of a local anaesthetic.
The aim of injecting corticosteroids is to reduce pain and inflammation sufficiently to enable exercises to be done and should be used in conjunction with physical therapy and correction of biomechanical factors.
If this also fail then surgery may be indicated to release the pressure on the nerve (called a surgical release).