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Flexor Hallucis Longus Tendinopathy

Presenting as pain around the inner ankle or along the bottom of the foot with movement of the big toe. It often occurs in people with flat feet and as a result of injury to another tendon.

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A graphic rendering of the legs and feet showing Flexor Hallucis Longus as well as the distribution of the distal sciatic nerve - including common peroneal and tibial nerves.

About FHL Tendinopathy

There are two main tendons that flex the big toe, with the bigger being: Flexor Hallucis Longus and the shorter being Flexor Hallucis Brevis

FHL attaches to the back of the fibula and runs behind the talus, under the inner ankle bone and then along the bottom of the foot and into the big toe. 

Due to it's position crossing the back of the leg then running along the inside of the ankle and along the length of the foot: FHL plays a key roll in balance, and is also the last point of propulsion during the gait cycle. 

Types of FHL Tendinopathy

FHL problems tend to occur either around the inside ankle or along the arch of the foot.

FHL quite often presents as a 'tenosynovitis', i,e, fluid along the tendon sheath, rather than as a gross tendonitis, but it can be tendinopathic in some cases.

When patients have tenosynovitis, it is not unusual for them to have some numbness or tingling in the bottom of the foot due to the pressure put on the nerves by the fluid. 

A person sitting down and flexing their right foot off the ground. They are pointing with their left hand to a region where the FHL would pass.
A graphic representation of the anatomy of the bottom of the foot including the paths of Flexor Hallucis Longus and Flexor Digitorum Longus.

What else could it be?

Flexor Hallucis Longus follows the path of other structures:

  • Flexor Digitorum Longus

  • Tibialis Posterior

  • The Plantar Fascia

  • Flexor Hallucis Brevis

  • Tibial Nerve

So, symptoms or dysfunction of this tendon might be as a result of any of these.

How are FHL tendon problems diagnosed?

Clinical examination and a thorough history is often adequate, however, in some instances it can be useful to use imaging to

  • Confirm the diagnosis

  • Identify how severe the problem is

  • Rule out other problems.

Imaging that can be used for FHL issues is:

  • Ultrasound scans (particularly dynamic)

  • MRI Scans

  • X-ray may be helpful in assessing deformity of the Os Trigonum.

An MRI of the foot, side on (sagittal view) which shows part of the FHL muscle belly and where the tendon passes behind the talus (ankle bone).
A person standing barefoot with their big toes lifted skywards. This is a type of exercise that might be used for foot pain.

How is FHL Tendinopathy treated?

The core of treatment for all tendinopathies is 'loading', so doing exercises. However, the types of exercises and positions used will vary according to the type of tendinitis. 

Other treatments for Achilles Tendinopathy include:

  • Rest (rare!)

  • Anti-inflammatories (rare!)

  • Shockwave therapy

  • High-volume image guided injections

  • Orthotics

  • Heel raises

  • Gait retraining

  • Soft-tissue mobilisation

How long does it take to cure FHL Tendinopathy?

The duration will vary based on:

  • Severity of the problem

  • Duration of the problem

  • How well patients stick to their treatment plan.

In my experience, patients with a very recent onset of pain can be back to functioning relatively normally within 2-3 weeks. 

If symptoms have been ongoing for more than a month, then it can be more persistent, but very manageable nonetheless.

It is usually essential to manage biomechanical issues causing FHL tendinopathy at the outset with orthotics and footwear.

No two people can be treated the same way when it comes to any medical issues, and the goal of how we treat patients is always to get you back to what you want to be doing. 

Lady running with her dog
Ready to say goodbye to your pain?

At Keep On Your Feet, we openly acknowledge that we cannot guarantee a cure for things: but we will work as hard as we can with you to help you reach your goals. 

If your symptoms fit the above, you will need to book a 'Foot Pain' consultation. This will be £95 and lasts approximately 60 minutes usually. If you need insoles, we'll give you some basic ones to try out (or some fancier ones and reduce their price!). 

This is a picture of Jeremy Ousey, director and podiatrist of Keep On Your Feet.

About the Author

Jeremy Ousey is the owner at Swansea's podiatry clinic: Keep On Your Feet. All the information found on this page was written by him (there's no AI or Chat-GPT here!), and has been carefully chosen to provide you with the information that you need to know about the condition. Jeremy has a Bachelor of Science in Podiatry, with honours, a Post-Graduate Certificate in Podiatric Sports Medicine, a Post-Graduate Diploma in Medical Ultrasound, and two Master's of Science degrees in the Theory of Podiatric Surgery, and Sports & Exercise Medicine. If you would like to know more about Jeremy, please click here.

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