groin pull | pulled groin muscle

It won’t come as any consolation to Matt Perry, the Bath and England rugby fullback, but he is not alone. Groin pain is a relatively common complaint among sportsmen and women, especially in those sports that involve kicking, twisting and turning. In Australian Rules Football, groin pain is one of the top three causes of missed games, after hamstring and knee injuries. There is a wide variety of possible causes (see below).

Major causes of groin pain among sportspeople

Common causes

adductor muscle strains
adductor tendinopathy
osteitis pubis
hip-joint pathologies (eg, degeneration, labral tears, non-specific synovitis)

Less common causes

ilio-inguinal nerve entrapment
psoas muscle and tendon pathology
conjoint tendon tears
stress fractures involving either the neck of the femur or the inferior pubic ramus
obturator neuropathy

It is the last on the list – obturator neuropathy – that has caused Perry’s troublesome and persistent injury. It is an entrapment neuropathy involving the obturator nerve, seen in Australian Rules footballers and track and field athletes, and more recently in ice-hockey, soccer and rugby players. The patients are usually, although not always, male.

Obturator neuropathy has a unique clinical presentation, in that it causes groin pain which is entirely exercise-related, having an almost claudicant quality to the pain (appears with exertion, goes away again at rest).

Pain is initially felt during exercise high up in the groin, usually at the adductor origin. With ongoing exercise the pain becomes more severe, and classically radiates down the inner thigh. Occasionally the pain is felt in the inner knee region (the Howship-Romberg phenomenon), and sometimes pain may be referred to the ipsilateral anterior superior iliac spine (outside hip on the same side). Alongside the pain, the athlete may describe a weakness or feeling of being unable to produce full power while running. Numbness is very rarely reported.

Examination findings at rest are variable. The patient may demonstrate weakness of resisted adduction, but their power may also be normal. Very rarely an area of parasthaesia to cold touch may be demonstrated over the distal inner thigh. In most cases, the patient will be tender over the obturator nerve, in the upper part of the groin lateral to the adductor longus tendon.

The diagnostic ‘gold standard’ for obturator neuropathy is to examine the patient after an exercise session in which they have brought on their symptoms. Examination will now reveal weakness of resisted adduction and an area of decreased sensation to cold touch all over the cutaneous distribution of the obturator nerve down the inner thigh.

The diagnosis of obturator neuropathy can be confirmed by needle electromyography (EMG), which shows chronic denervation of the adductor muscle group. It is important to perform the EMG studies when the patient has been recently symptomatic. In our experience, if the patient has been asymptomatic for more than two weeks, the EMG studies are likely to be normal and the diagnosis may be missed. Radionucleotide bone scan may show increased uptake over the ipsilateral pubic tubercle. This may represent a periostitis (inflamed surface) of the pubis as a result of the abnormal tension of the adductor fascia.

Conservative treatment options for obturator neuropathy include heavy soft-tissue massage, neuromeningeal stretches, and a period of rest. But in most cases these measures will not solve the problem. Occasionally corticosteroid injection into the region of the obturator nerve, under fluoroscopic control, has been attempted, and in some cases this has given temporary symptomatic relief, but invariably the symptoms return over time.

The definitive treatment of this condition is surgical. A small transverse incision is made in the proximal groin near the origin of the adductor longus muscle. The tissue plane between the adductor longus and the pectineus in explored, revealing the obturator nerve under the fascia over adductor brevis. This fascia is released and the nerve is explored and released, distally and proximally to the obturator tunnel, where the nerve exits the pelvis. The skin and subcutaneous layers are closed, and the patient can usually leave hospital within 24 hours.

Rehabilitation includes gentle massage, neuromeningeal stretches and a gradual return to activity, culminating in a return to sport four to six weeks after the procedure.

The pathology of obturator neuropathy is not yet understood, but it appears that fascial dysfunction plays a role in the development of the neural irritation. There is also some evidence that this fascial dysfunction may be a precursor to the development of osteitis pubis, although this has yet to be proven scientifically.