Each foot consists of 28 bones, several intrinsic muscles, ligaments and tendons from the extrinsic muscles of the lower leg that influence foot function. Many foot pathologies arise from the abnormal movements of the complex joint structures within the foot. These abnormalities can also cause related knee, hip and back problems. Most of these biomechanically related problems are slowly progressive in nature. 1,2,3,7,14,17,18
Below the ankle joint there exists a joint complex called the subtalar joint. This complex joint moves through all three body planes simultaneously. Its movement and range of motion is translated up into the leg in the form of tibial rotation and into the foot distally causing the locking and unlocking of another joint complex called the midtarsal joint.
The Effect of an Abnormal Subtalar Joint on the Knee
The effect of the subtalar joint on the knee as it causes the internal and external rotation of the tibia is a change in the orientation of the patella and the patella tendon. In an abnormally functioning subtalor joint this rotation of the tibia causes the patella to ride abnormally with its articulation with the femur. This common cause of chrondomalacia patella is rarely addressed or recognized. Additionally, with excessive rotation of the tibia, the collateral ligaments are strained. 3,7,12,15,16,17,19,20 Countless numbers of arthroscopic knee surgeries are preformed to correct the damage caused by an abnormally functioning subtalar joint in the foot. Even more rare is follow up treatment following the surgery to address the cause of the patellar damage. As a result, continued deterioration of the knee joint is allowed to continue.
Abnormal Subtalar Joint Motion and the Posterior Tibial Tendon
In the foot, the movement of the subtalar joint influences the locking and unlocking of the midtarsal joint complex which is distal to the subtalar joint. When the subtalar joint functions abnormally, the locking and unlocking of the midtarsal joint functions abnormally and results in a number of foot pathologies. 1,2 One such problem is an insidious slowly progressive problem that may occur is excessive strain on the posterior tibial tendon as it passes distal to the medial malleolus. Over time this important tendon becomes dysfunctional. The result is the development of chronic tears and central degeneration of the tendon. This condition occurs more commonly in women than men with the chronic form becoming symptomatic in the fourth or fifth decades of life. The consequence of this condition is chronic pain and a significant limitation of activities (See painful adult flatfoot). Early treatment consists of a below the knee cast in an attempt to heal the tendon damage followed by wearing a functional foot orthosis to correct the abnormal function of the subtalar joint. In severe cases, surgical intervention requiring subtalar joint fusion is necessary. 4,7,8,9,10,11,14, 23
A more common consequence of an abnormally functioning subtalar joint is plantar heel pain. This condition is often referred to as heel spur syndrome. The genesis of this problem is an abnormally functioning subtalar joint which causes the foot to pronate excessively or for a longer than normal duration during the gait cycle. As this occurs, a thick fibrous ligament called the planter fascia that is attached to the plantar aspect of the heel and fans out across the arch of the foot into the ball of the foot, is stretched excessively. This ligament begins to develop small tears where it attaches into the heel causing pain. Treatment directed at the cause of the problem, abnormal subtalar joint motion, consists of using a functional foot orthosis that corrects the abnormal subtalar joint motion. 4,5,6,7,14,18,20,21,22
Bunions, Talors Bunions and Neuromas
In other instances of abnormal subtalar joint function, the abnormal locking and unlocking of the midtarsal joint results in the abnormal movement of the long bones in the forefoot called the metatarsal bones. As this occurs, splaying of the metatarsals causes a widening of the forefoot.Over time, this positional abnormality becomes a fixed functional deformity resulting in the formation of a bunion (hallux abductovalgus deformity with bunion) and or a tailors bunion deformity. 1,2,24,25,26,27,28,29,30 The abnormal movement of the metatarsal bones can also result in the compression of the interdigital nerves in the ball of the foot causing neuromas. Neuromas in the forefoot are nothing more than a swelling of the interdigital nerve as a result of chronic irritation from the abnormal movement of the metatarsal bones, which pinch the nerve. This causes swelling and damage to the nerve. 1
The abnormal locking and unlocking of the midtarsal joint also results in an imbalance between the tendons on the top of the toes (extensor tendons) and the tendons on the bottom of the toes (flexor tendons). When this occurs, digital contracture results. The resulting hammertoe deformity progresses from a flexible positional deformity to a rigid and fixed functional deformity. 1
Treatment of Foot Pathology with Functional Orthotics
As with all progressive medical conditions, it is best to initiate treatment early. Conservative care directed at alleviating symptoms and slowing or halting the progression of the pathology is most desirable. This is accomplished with a custom-fabricated functional orthotic device made from a durable semiflexable polypropylene material. 4,5,6,10,14,16,19,20,22,23
The device must be made to the unique specifications of the patient if they are to accomplish the desired result. They must also be constructed to fit in normal shoe gear if possible. If the patient cannot easily wear the device then treatment failure is certain.
To capture the correct specifications for the prescription of the orthotics, the prescribing physician must have a through understanding of lower extremity function. The plaster of paris molds of the foot must capture the proper position of the foot. This position is determined by the treating physician based upon measurements of the subtalar joints and midtarsal joints of the foot and the quality of their ranges of motion in relationship to the other joints of the foot and leg. A through practitioner will perform these measurements and then evaluate them relative to a brief weight bearing gait analysis.
It is this author's opinion that the treating physician can only accomplish this adequately in the physician office. In this instance, all of the elements are present to construct the appropriate custom-made device that the patient will wear. To further ensure success, the physician must have access to orthotic laboratories that understand the proper construction of a functional orthotic and one that is willing to communicate with the physician in the direction of the construction of the orthotic.
Quite often foot, deformities will progress beyond the ability to successful treat them with functional orthotics. In these instances, surgical intervention is often necessary. It must be kept in mind, however, that surgical procedures to correct these deformities do not address the cause of the deformity. Just as the knee joint will continue to deteriorate following arthroscopic surgery if the offending condition is due to an abnormally functioning subtalar joint, so will foot deformities following surgical treatment. Generally following surgery, there is a period of relief; but many of these deformities will slowly reoccur unless the abnormal subtalar joint function is addressed .To address the reoccurrence of these abnormalities, a functional orthotic should be prescribed.
Many back, hip, knee, and foot abnormalities are caused by the abnormal function of a joint complex in the foot called the subtalar joint. The relative occurrence of these abnormalities can be related to the relative proximity to the subtalar joint. Therefore, the majority of pathology that arises out of an abnormally functioning subtalar joint occurs in the foot, fewer occur in the knee, and fewer yet occur in the hip and low back.
Relative to the cost of treatment for these conditions, an orthotic case fee is often the most cost-effective treatment plan. Additionally, the use of orthotics following surgical intervention of chrondromalecia patella, posterior tibial tendon reconstruction, subtalar arthrodesis, planter fascial release, heel spur surgery, bunion or tailors bunion surgery and others are useful in the prevention of reoccurrence of the deformity.
A relevant point of consideration in the successful treatment of knee and foot pathology with functional orthotics is to allow the prescribing physician, who has the knowledge and experience in the treatment of these abnormalities, to maintain complete control of the casting, measuring and choice of fabricating laboratory. None of these elements should add to the cost of the devices. Should the health plan set their fees below a level adequate to reimburse the physician for the time, expertise and outside laboratory fees, then the physician will refer the patients to an outside source not equipped to meet the patients needs and more costly treatments will eventually be needed.
References 1. Root, Weed, Orein Normal and Abnormal Functioning of the Foot (Clinical Biomechanics Corp, Pub 1977 LCC# 71-185067)
2. DeValentine, Foot and Ankle Disorders in Children,(Churchill Livingstone Pub 1992
3. Klingman RE, Foot pronation and patello-femeral joint dysfunction (J. Orthop Sports Phys. Ther 1999 July)
4. Sobel E, et al; Orthoses in the treatment of rearfoot problems (J Am Podiatr Med Assoc, 1999 May)
5. Tisdel CL, et al: Diagnosing and treating plantar fasciitis: a conservative approach to plantar heel pain ( Cleve Clin J Med, 1999 April)
6. Lynch DM et al Conservative treatment of plantar fasciitis, A prospective study (J Am Podiatr Med Assoc, 1998 Aug)
7. Krivickas LS Anatomical factors associated with overuse sports injuries (Sports Med 1997 Aug)
8. Dyal CM et al Pes planus in patients with posterior tibial tendon insufficiency: asympotomatic versus symptomatic foot (Foot Ankle Int 1997 Feb)
9. Kitauka HB et al Effect of the posterior tibial tendon on the arch of the foot during simulated weight bearing, biomechanical analysis (Foot Ankle Inst, 1997 Jan)
10. Beals TC et al: Posterior tendon insufficiency diagnosis and treatment (J Am Acad Orthop Surg 1999 Mar)
11. Smith CF Anatomy, function and pathophysiology of the posterior tibial tendon (Clin Podiatr Med Surg, 1999 July)
12. Klingman RE et al The effect of subtalar joint positioning on patellar glide positions in subjects with excessive rearfoot pronation, (J. Orthop Sports Phys Theer, 1997 Mar)
13. Scranton PE et al Pathologic anatomic variations in subtalar joint anatomy (Foot Ankle Int 1997 Aug)
14. Steb HS et al Conserative management of posterior tibial tendon dysfunction, subtalar joint complex and pes planus deformity (Clin Podiatr Med Surg 1999 July)
15. Reischl SF et al Relationship between foot pronation and rotation of the tibia and femur during walking (Foot Ankle Int, 1999 Aug)
16. Handley A et al; Antipronation taping and temporary orthoses. Effects on tibial rotation position after exercise (J Am Podiatr Med Assoc, 1999 Mar)
17. Hinterman B et al Pronation in runners, Implications for injuries (Sports Med, 1998 Sept)
18. Busseul C et al Rearfoot – forefoot orientation and traumatic risk for runners (Foot Ankle Int 1998 Jan)
19. Way MC Effects of a thermoplastic foot orthosis on patello-femeral pain in a collegiate athlete: a single subject design (J Orhtop Sports Phys Ther, 1999 Jun)
20. Leung AK et al Biomedical gait evaluation of the immediate effect of orthotic treatment for flexable flatfoot (Prosthet orthot Int, 1998 May)
21. Cornwall MW et al Three – dimensional movement of the foot during the stance phase of walking (J Am Podiatr Med Assoc 1999 Feb)
22. Van Wyngarden TM The painful foot Part I Common forefoot deformities (Am Fam Physicians 1997 Apr)
23. Van Wyngarden TM The painful foot Part II Common rearfoot deformities (Am Fam Physicians 1997 May)
24. Goldner JT, Gaines RW: Adult and juvenile hallux valgus: analysis and treatment. (Orthop Clin North Am 7:863, 1976)
25. Halebian JD Gaines SS Juvenile hallux valgus, (J Foot Surg 22:290, 1983)
26. Scranton PE Zuckerman JD Bunion surgery adolescents; results of surgical treatment (J Pediatric Orthop 4:39, 1984)
27. Hardy RH Clapham JC Observations on hallux Valgus (J Bone and Joint Surg 33:376 1951)
28. Amarnek DL Jacob AM Oloft LM Adolescent hallux valgus, it etiology and surgical management (J Foot Surg 24:54 1985)
29. Inman VT Hallux valgus: a review of etiologic factors (Orthop Clin North Am 5:59, 1974)
30. Kalen V Brecher A Relationship between adolescent bunions and flatfeet. (Foot Ankles 8:331, 1988)