Lateral Thigh Pain – Meralgia Paraesthetica

Meralgia paraesthetica is one of the many localised pain syndromes which can present to a musculoskeletal physiotherapist, with symptoms of tingling, numbness and pain in the anterior and lateral aspects of the thigh. The symptoms were linked with the idea of a local nerve suffering compressive forces not long after its initial description in the 19th century. The lateral femoral cutaneous nerve is the culprit and is solely a sensory nerve, having no muscular function and merely supplying the skin sensibility over the relevant thigh areas. It is not clear how often this syndrome occurs but it is likely to be under diagnosed.

There are many musculoskeletal conditions which could send pain to this general area and which can be confused with this neural problem, including trochanteric bursitis, spinal referred pain and spinal nerve compression. The commonest reason for this condition is abnormal pressure on the nerve in specific parts of its track where it is vulnerable. This has been linked to wearing an over tight belt and to being generally overweight. The syndrome may also be brought on by surgery near the area such as bone graft, hip replacement and quadriceps.

There are several areas along the length of this cutaneous nerve where it can suffer compression, as it exits from inside the psoas muscle, courses in close proximity to the inguinal ligament, runs close to the bony lip of the front of the pelvis and finally emerges into the thigh through the tough layer of connective tissue called the fascia lata. A neurapraxia is the name given to this least damaging form of nerve compressive damage in which case the nerve loses some of its sheath of insulation known as the myelin sheath.

The nerve axon itself is not affected in this injury and this is the nerve injury which recovers well and most quickly, taking a very short time up or to several months to resolve. A more severe injury, where the axon is disrupted, is known as axonotmesis and results in the whole nerve axon degenerating along its length. It then has to regrow at its very slow speed, meaning this kind of injury can take a long period to resolve even though it may do so in the long term. If a nerve is so badly injured that its ends are not in contact any longer then the chances of recovery without surgical intervention are very low.

On examination the patient’s history should include enquiries about any traumatic events which could have a bearing on the condition. Physical examination will find altered sensibility in the front and side of the thigh, symptoms which include pain, burning, numbness, reduced feeling and pins and needles. The usual onset of symptoms is gradual and slow and they do not go beyond the knee area, with pain often sharper and burning but can also be a duller ache. The area of symptoms on the thigh can vary with the severity of the conditions, with exclusively anterior or lateral thigh symptoms reported.

The initial goal of treatment is to establish where and what the problem of compression is likely to be, as correcting a tight belt, fitted clothing or heavy objects carried on the waist can be a useful first strategy. Loss of weight in obese patients can be sufficient to change things so that some symptom resolution is achieved. The ergonomics of work may also be important to eliminate obviously risky postures or movements. A doctor may give corticosteroids or anaesthetic drugs by local injection to limit the inflammatory changes or break the pain cycles.

The surgeon has to be very aware of the variations in the anatomical position of the lateral cutaneous nerve in order to inject or operate successfully. On release of the nerve compression the syndrome tends to recover without further intervention. If changes in functional activity do not resolve the pain, injections or surgery are further options, with neurolysis, cutting the nerve and decompression potential options. Decompression may be necessary at several different sites where the nerve is vulnerable. Scientific reports following groups of patients after surgery have generally reported good recoveries.

Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about physiotherapy, physiotherapy, physiotherapists in Leeds, back pain, orthopaedic conditions, neck pain and injury management. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK.