Pain behind the ankle

Diana’s pain behind the ankle was pointing her therapists in the wrong direction. David Joyce unravelled the mystery

This is a case of mistaken identity of a reasonably well known complication following ankle sprains. It took a bit of sleuthing and experimentation to get to the bottom of it and shows the tricky nature of some pathologies, stubbornly refusing to obey the text books!

A couple of months ago, Diana, one of the world’s best taekwondo athletes, was sparring and felt a sudden sharp pain at the back of her ankle that caused her to drop to the ground in agony. No sooner had she landed on the ground than the pain disappeared and she was ready to continue fighting. She’d experienced the same phenomenon a number of times over the past couple of years, but she was worried that this time it was worse and could seriously jeopardise her medal chances at the next Olympics.

Taekwondo

Taekwondo is a martial art that originated in Korea. It made its Olympic debut at the Seoul Olympics in 1988 as a demonstration sport and became a full medal sport at the 2000 Sydney games. It is a full-contact combat sport that pits opponents of similar weight against each other in a match of three rounds, each lasting two minutes.

The principal way of scoring points is to kick the opponent’s chest protector (one point) or head (two points), although on occasions, one point may be awarded for a punch to the chest that stops the opponent in their tracks. It is one of the most dynamic Olympic sports, combining strength, power, speed, agility and flexibility. Unsurprisingly, taekwondo competitors are vulnerable to a range of injuries, one of the most prevalent being ankle sprains, another being Achilles tendinopathy, because of the amount of jumping the sport demands.

The symptoms don’t fit

As physiotherapist for the Great Britain national team, I see a lot of these injuries, but Diana’s case was baffling. I was able to locate her pain precisely at the mid-third portion of her left Achilles tendon (as per Achilles tendinopathy or parateninitis), but the pain was elicited with forced plantar flexion (as per posterior ankle impingement). Specifically, Diana would be almost totally pain-free unless she kicked a pad or body armour awkwardly, forcing her ankle into the extreme of plantar flexion.

[077-FIG1]

Now, Diana is a tough girl who bears the scars of numerous operations. And although she was always back up on her feet within a minute or so after an awkward kick that produced this agonising pain, the repeated occurrences were starting to dent her confidence in using her left foot to kick with. As a result she was significantly altering her fighting style and limiting her weaponry.

Because Diana was able to precisely palpate her pain on her Achilles tendon, many of the physios who had seen her in the past had assumed it was a tendinopathy and prescribed the standard heel drop programme (see tendinopathy articles in SIB 76). But since the aggravating movement was plantar flexion, these rehab regimes usually had the effect of making this worse, causing Diana to become disillusioned.

Looking for patterns

In general the pain seemed to come and go; Diana could go for some months without a problem, and then, apparently all of a sudden, the pain would strike again with a vengeance. She could find no real pattern to help explain it.

When I first saw her for this problem, I was confused because she was presenting with some, but not all the signs, of two separate and distinct pathologies: posterior ankle impingement and Achilles tendon/paratendon pathology.

Posterior ankle impingement (also called tarsal compression or os trigonum syndrome) is often seem in ballet dancers, who repetitively plantarflex the ankle as they assume the pointe and demi-pointe positions. Downhill runners are another group of athletes who complain of this condition, as are fast bowlers in cricket. There are a number of structures at the back of the ankle that may become pinched when the toes are pointed down. These include:

* an os trigonum (see box, above right)

* flexor hallucis tenosynovitis (inflammation of the sheath surrounding the tendon that flexes the big toe)

* talus osteochondritis (flaking of the cartilage of the talus bone of the ankle complex).

The mechanism of Diana’s pain was clear, and it should have been a safe bet that she was suffering from posterior impingement. And yet… palpation of the posterior recess of her ankle was completely pain-free – as previously mentioned, her pain was located around the middle of her Achilles. Indeed, if I palpated the tendon at that point, she said that that was ‘her pain’. Certainly not your average posterior impingement.

An ultrasound scan showed no tendon abnormality and a follow-up MRI confirmed this; but it did show some fluid around the subtalar joint and the posterior gutter. Consultations with an equally bemused foot and ankle surgeon and eminent musculoskeletal radiologist shed no further light on the problem. Sometimes, MRI will show up things (such as the fluid) which are simply coincidental, and in diagnostic terms red herrings. And there was absolutely nothing on the scans that pointed to a problem at the site of Diana’s pain.

Steroid injection

In the absence of a definitive diagnosis, but on the basis that her mechanism of pain was very similar to posterior impingement, it was decided that the best course of action was a diagnostic/ therapeutic steroid injection into the posterior ankle recess. Diana noticed an immediate reduction in her pain and to the amazement of the radiologist and me, even palpation of the Achilles was pain free.

So we had a diagnosis but still no cause. Posterior impingement, like anterior ankle impingement, is often precipitated by a bad ankle sprain. Diana had not sprained her ankle, so there must have been another mechanism at work in her case. The average person has about 35 degrees of ankle plantar flexion available to them. Diana’s range was almost 50 degrees. I think what has happened is that during her 15 years of taekwondo practice, Diana’s repeated plantar flexion has stretched the structures at the front of her ankle to such an extent that she constantly abuts the calcaneus against the posterior aspect of the talus (see Figure 1, above). Very gradually this has set up an inflammatory reaction.

Often after a combined local anaesthetic/steroid injection the initial pain relief is brought about by the anaesthetic, because the steroid is in crystalline form, which takes a little longer to take effect. This creates a hazard in the first few days after the injection, because the athlete may feel as though they are ‘cured’ and consequently push themselves too hard, further irritating the joint and never truly allowing the steroid to settle the inflammation. We often find such athletes coming back to us after six weeks, declaring the whole process has failed. I have learned to be a bit more cautious these days: I placed Diana in an Aircast walking boot for almost a week and only gradually reintroduced her to kicking.

Rehab measures

Given the nature of the sport and the debilitating (if ephemeral) nature of the pain Diana had been confronted with in the past, it is important that we take measures to avoid further relapses. She clearly does not want to be doing sustained, end-of-range anterior ankle stretches, so the coaching staff have been advised to eliminate any such movements from her programme. In intense training periods, Diana now has her ankles strapped to reduce the plantar flexion moment on the ankle, thereby reducing the posterior compression. She is back in full training and reports that her ankle complex has not felt this good for a couple of years.

I think this case demonstrates nicely the valuable role that diagnostic anaesthetic injection can play for the sports therapist.

By using ultrasound guidance, we were able to ensure that we were in precisely the right area and get immediate feedback from Diana as to the effectiveness of the intervention. This technique can be used to great effect in other parts of the body and is a costeffective and rapid means of differential diagnosis.

For example, sometimes it can be tricky to distinguish between acromio-clavicular joint pathology and labral (shoulder cartilage) damage, because often both injuries are provoked by similar tasks and movements (such as bringing the arm across the body). If the AC joint is indeed the culprit, an injection of local anaesthetic into the easy-to-locate joint should kill the pain when the athlete reaches across their own body. Treatment can thus be very easily directed to the source of the problem.

Thankfully for Diana, her chief weapon (her right foot) should no longer prove to be her Achilles heel!