Medial Ankle Pain – FHL Injury
An injury to the Flexor Hallucis Longus (FHL) tendon causes medial ankle pain or pain on the bottom of the foot. FHL injury is a condition that is often overlooked or misdiagnosed. This injury affects dancers, runners, soccer players, and any other athlete who performs repeated, propulsive forces, or jumping. Injury of the FHL muscle is sometimes called “Dancer’s tendonitis” but it is not solely limited to dancers.
The FHL muscle allows you to point your big toe (plantar-flexion of the big toe) and stabilizes the subtalar joint. The subtalar joint is located between two bones in your ankle – the talus and the calcaneus.
The subtalar Joint allows movement of the heel toward the medial plane (inversion) as well as movement of the heel towards the lateral plane (eversion).
Anatomy/Biomechanics of Medial Ankle Pain
The Flexor Hallucis Longus muscle is located deep under your calf muscles (the most lateral muscle of the deep compartment). The FHL originates on the lateral lower leg (distal two-thirds of Fibula).
It then travels at an oblique angle, crossing the posterior surface of Tibia, down towards the medial ankle (posterior surface of talus) and travels under a part of the heel bone (sustentaculum tali of the calcaneus). The FHL then passes under the sole of the foot (between the two heads of the Flexor Hallucis Brevis) and inserts into the base of the big toe (base of the distal phalanx of Hallax).
As mentioned, the FHL Tendon curves around a structure called the sustentaculum tali. This is a bony section on the inside of the calcaneus. This is often a site of friction and irritation for the FHL tendon. The FHL tendon also travels between the two sesamoid bones just behind the big toe (metatarso-phalangeal joint). The sheath that surrounds the FHL tendon is often irritated.
Causes and Presentation of Medial Ankle Pain
The repetitive motion of pushing-off with your foot (plantar flexion) during dance, running, soccer, and jumping can cause injury to the FHL.
Injury to the FHL tendon and muscle can present in a variety of ways – sometimes involving inflammation and sometimes not. Injury to the tendon without inflammation is refer to as a “Tendinopathy”. Tendinopathy refers to a degenerative lesion in the tendon without affecting the tendon sheath that surrounds the tendon.
When FHL inflammation (tendonitis) is present in the foot, it usually occurs in one of the following three locations.
- Inside of the ankle (fibro-osseous tunnel along the posteromedial ankle).
- At the “Knot of Henry” – a section just behind the big toe (first metatarsal) where the FDL muscle crosses the FHL tendon.
- Just behind the big toe by the sesamoid bone. (A sesamoid bone holds its tendon away from the center of the joint and acts to increase mechanical force).
When the FHL tendon becomes nodular, a condition called Hallux Saltans can develop. Hallux Saltans is similar to trigger finger in the hand, except it occurs in the big toe. Triggering of the toe occurs when the nodular thickening of the tendon snaps through the fibro-osseous tunnel. This causes a jerking motion, much like a trigger finger.
If not addressed, Hallux Saltans can contribute to the progression of an additional condition called Hallux Rigidus. Hallux Rigidus means “stiff great toe”. Hallux Rigidus is the second most common disorder of the first MTP joint. The most common injury is a bunion – otherwise known as Hallux Valgus.
Special Considerations for the Dancer
Injury to the FHL in dancers is often caused by the repetitive motion of changing position from a plié position to a relevé position. This action produces a force that is 10 times the dancer’s body weight.
Ideally, for greater stability and increased propulsion, the foot should be in a supinated position at the heel during push-off. For a dancer, any action that causes a reduction in plantar flexion motion can create an FHL injury. Biomechanically, a lack of plantar flexion leads to a prolonged pronation position of the foot when pushing off in the Propulsion Phase.
In dancers, the FHL tendon is often compressed while performing a relevé position and is over-stretched while performing a plié position. In such a case, the dancer will feel posterior medial ankle pain when performing the plié.
Diagnosis and Imaging – FHL Injury
X-rays for this condition are not very specific. X-Rays are good for ruling out fractures (calcaneus, distal medial malleolus, or Os Trigonum) that may cause an impingement of the FHL tendon. It is important to note that X-Rays will not provide a definitive diagnosis of FHL injuries.
A good history is much more definitive, especially when accompanied by a full physical examination and an MRI. MRI imaging is an excellent resource for showing damage to tissue fibers, inflammation, and swelling (edema).
If the MRI is not available or is too expensive, a CT scan (Computed Tomography) can prove to be a useful alternative.
Treatment of Medial Ankle Pain
In most cases, FHL syndrome (involving partial tears, tendinosis, or inflammatory conditions) responds well to conservative care. However, a complete tear of the FHL tendon may require corrective surgery since serious cases of FHL injury can cause the end an athlete’s career.
Conservative care includes:
- Ice or heat depending on stage and type of injury (inflammation or not). See our Icing and Heating blog.
- Reduction in activity. Usually, some modification in all activities is necessary.
- Supports (crutches or walker boot) can be beneficial.
- Taping – Kinesio Taping. At Kinetic Health we use SpiderTech Kinesio-taping.
- Soft-tissue and joint mobilization (Active Release, Graston Techniques, Massage, and Manipulation) are all therapies that we use at Kinetic Health.
- Inflammatory strategy implementation (medication for no longer than seven days). See our page about Reducing Inflammation.
- Exercises for increased strength, flexibility and balance. Go to www.releaseyourbody.com for exercises you can use to treat this condition.
- Biomechanical corrections (footwear or Kintec Orthotics) such as those recommended or provided at Kinetic Health for patients suffering from these conditions.
- A gradual return to activities.