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What is it, why does it occur and how can it be treated?
Plantar fasciitis is the most common complaint that presents to Podiatrists. Plantar fasciitis means inflammation of the plantar fascia. Plantar Fasciitis or fasciosis most often occurs in people over the age of 40 who have embarked on a change of physical activity, they would also have structural and functional pathology that compromises the efficiency of foot function.
This structure spans the plantar surface of the foot from the plantar aspect of the proximal phalanges of the toes to the plantar aspect of the calcaneus. It is fibrous tissue, similar to a ligament in that it has no muscular attachment causing stretch or relaxation of the tissue. Having said that, some of these fibres wrap around the calcaneus and link with the Achilles tendon. As a result, tension within the posterior compartment muscles of the lower leg can influence the tension within the plantar fascia. So too, dorsiflexion and plantar flexion of the toes will tighten or loosen the plantar fascia.
Anatomically, the plantar fascia is situated deep to the skin and superficial adipose tissue on the plantar surface of the foot, but superficial to the intrinsic muscles and tendons of the foot. The plantar fascia, together with ligaments on the plantar aspect of the joints of the rear and midfoot, is an important component of the soft tissues that support the longitudinal arch.
On weight bearing, pronation of the subtalar joint unlocks the midtarsal joint causing the longitudinal arch of the foot to lower. This elongation effect on the arch stretches the plantar fascia. In turn, the increased tension may reduce the available dorsiflexion on the toes, especially the hallux. If the pronation is excessive, in compensation for lower limb structural pathology, the posterior compartment, or supinating, lower leg muscles may also contract which may increase the tension within the plantar fascia.
During gait, with absence of any structural and functional pathology, the foot will pronate at heel contact and through midstance. This allows for shock absorption and adaptation to the supporting surface. During late midstance, resupination is initiated by external rotation of the lower limb together with contraction of the posterior compartment muscles of the lower leg. This subtalar supination creates a locking effect of the midtarsal joint, stabilising the forefoot which facilitates plantar flexion of the 1ST metatarsal through contraction of the peroneus longus. This reduces tension within the plantar fascia, allowing dorsiflexion of the hallux, creating an efficient propulsive lever of the 1ST ray.
All this changes with lower limb structural and functional pathology that causes excessive compensatory pronation of the subtalar joint and oblique midtarsal joint axis. This upsets the normal sequence of pronation and resupination of the foot. Prolonged pronation will result in tightness of the plantar fascia during the propulsive phase of gait and a functional hallux limitus. To facilitate propulsion, an abductory twist of the lower leg around the restricted 1ST MTP joint may occur creating other torsional stress within the foot and lower limb. Other pathology may develop, such as osteoarthritis of the 1ST MTPjoint and hallux abductor valgus deformity (bunions).
Forefoot malalignment, such as forefoot valgus and or plantar flexed 1ST ray that occurs with a high arched or cavus foot type is compensated by midtarsal joint longitudinal axis (LMTJ) supination. This has the effect of unlocking the forefoot and allowing the ground reaction force to dorsiflex the 1ST metatarsal and tightening the plantar fascia creating a functional hallux limitus with restricted dorsiflexion of the 1ST MTP joint. Plantar flexed 1ST rays are compensated by both LMTJ supination and subtalar joint (STJ) supination. This does not, unfortunately, offload the plantar fascia, but gives the treating therapist the illusion that the foot is functioning in a normal position, because of the lack of STJ pronation.
The main structure to suffer with this abnormal function is the plantar fascia. The continual overstretch of the medial band of the plantar fascia irritates the attachment on the plantar surface of the medial condyle of the calcaneus. Inflammation of the fascia as well as the bone tissue occurs, causing pain.
The pain is felt on weight bearing, usually after periods of rest. At rest, in a relaxed position, the weight of the foot causes plantar flexion of the ankle relaxing the calf muscle and Achilles as well as the plantar fascia. However, on initial weight bearing, the foot pronates with subsequent lowering of the arch structure and stretch of the inflamed plantar fascia. After standing and walking for a short period, which stretches the plantar fascia, the severity of the pain reduces but will be exacerbated by prolonged weight bearing activity.
What causes it?
Plantar fasciitis may develop after an acute traumatic episode such as an unexpected step down off a curb, or following excessive, increased physical activity. Often the sufferer will expect this condition to automatically resolve and therefore does not seek medical assistance. As a result, when presenting at a clinic, this condition is often chronic and should be termed ‘Plantar fasciosis’ with possible calcaneal bone spurring and bone oedema. Prolonged inflammation will often result in thickening and weakening of the fascia just distal to the calcaneal attachment, sometimes with fascial tears or longitudinal splits. Sometimes there will be inflammation along the total length of the fascia with pain in the forefoot. Often a branch of the tibial nerve, ‘Baxter’s nerve, can become irritated by the chronic inflammation causing pain to be felt on the medial aspect of the heel.
Complications that sometimes arise with chronic plantar fasciosis are:
- Plantar heel pain from bone oedema created by the constant pull of the tight fascia at the calcaneal attachment. Additional cushioning may help to resolve this pain.
- Longitudinal tears or splits within the fascia with associated increase in volume from the inflammation. This swelling increases the pressure from the surface of an orthosis or shoe innersole.
- Sometimes the chronic inflammation can lead to weakness of the fascia and tears which heal with localised scar tissue nodules. Accommodation for these nodules must be provided in the orthotic shell contour.
- Chronic inflammation of the fascia can spread to those fibres surrounding the heel fat pad with cutaneous nerve irritation and pain. Likewise, Baxter’s nerve, a branch of the Tibial nerve can also become irritated.
Treatment of Plantar fasciitis or fasciosis must involve addressing the underlying functional pathology, especially forefoot stability. Typically, when first presented, a therapist will prescribe anti-inflammatories as well as rest. However, if the underlying functional pathology persists, then so will the condition, especially on resumption of activity. Taping the foot with ‘sports tape’ that maintains a relatively supinated position will allow pain free weight bearing activity for a short period. Effectiveness of this taping technique will help the therapist determine if functional orthoses will be effective. Likewise, the wearing of an air-cast boot to limit ankle movement and foot function will help to reduce the symptoms. A ‘Strassburg Sock’, which maintains the foot in a dorsiflexed position while resting, stretching the fascia and calf muscles, may also assist to relieve symptoms and promote healing of the inflamed fascia while in a stretched position.
For long term resolution and prevention of further foot pathology and return of the fasciitis, prescription function orthoses are a must, together with appropriate footwear to support the foot in a functionally efficient position. A thorough biomechanical examination (BME) to determine lower limb alignment, range of motion and forefoot to rearfoot relationship needs to be conducted. An accurate cast or 3D scan, duplicating the forefoot to rearfoot relationship found during the BME is then taken and sent to a laboratory together with the orthotic prescription for the manufacture of the orthoses.
The patient should experience immediate comfort and relief of the plantar fascial symptoms on wearing the orthoses.
Other treatment modalities, such as Shockwave Therapy and InterXtherapy can assist in resolution of Plantar fasciosis. Daily calf muscle and fascial stretches are necessary regardless of any other therapy.
If you suffer from plantar fasciitis, book an appointment with one of our podiatrists for an assessment.