Can Foot Orthoses Have An Impact For Knee Osteoarthritis?
Dr. Kevin Kirby, DPM Given the common nature of knee
Years ago we redesigned our prescription form to not only include specifications for orthotic fabrication, but also biomechanical examination findings, patient history, and measurements. This information is handy for practitioners to have in one document in the patient’s file, but also for your orthotic manufacturers to have a complete picture of the case. From this information the type of orthosis, posting systems, additional requirements and ultimate success of your treatment will be determined.
We will briefly review these sections to enhance clarity and understanding when supplying this vital information.
** Please always include the patient’s weight and shoe size. This information is vital in fabricating the right device for your patient.
PATIENT HISTORY
- Occupation- should be considered when choosing the rigidity or flexibility of the shell. For example, a construction worker should be in an unbreakable and durable shell to withstand the uneven terrain and heavy load they would place on the orthotic. Shoe fit is likely not a concern due to the large safety boots in which the device is worn. An office worker, on the other hand, would require a less bulky device in order to fit into dress shoes. The type of movements, forces applied, and amount of time standing on the feet can vary widely with different occupations.
- Sports/Activity level- this is helpful in determining if the sport the orthotic is used for is multidirectional or unidirectional, the type of shoe needed to fit (walking shoe versus a narrow soccer cleat), as well as the variety of forces that may be applied to the device.
- Type of Footwear- various types of footwear will require different grinds of the orthotic. As well, some types of shoes are not compatible with everyday styles of orthotics. For example, low profile dress shoes are high heels may require a Classic Dress or Dress Flex style in order for the device to fit into the shoe.
- Chief complaint- it’s good to be specific here. For example, if heel pain is at the plantar insertion of the plantar fascia a decrease in the calcaneal inclination angle may be considered. If, on the other hand the pain is on the posterior aspect of the calcaneus, heel raises may be considered. Specific pain symptoms can determine certain padding or accommodation requirements.
- Other complaints (leg, knee, hip, back) – as with the chief complaint, certain symptoms can help determine the type of device and additions that may be required. As well, asking questions relating to this section will help the patient realize how the foot affects other areas of the body.
EXAMINATION FINDINGS
- Foot appearance- we ask you to note the difference in the arch height on weight bearing and non weigh nearing to determine if we are dealing with a flexible or rigid foot. There are definitely shades in between. Posting systems are quite a bit different for high arched, rigid feet as compared to high arched, flexible feet. The feet of some patients can appear quite rigid non weight bearing due to the patient not being relaxed. This simple comparison can quickly determine if this is the case.
- Foot motions- again this category is used to determine the degree of flexibility. As a rule a foot that has very loose range of motion can take full posting control; whereas a rigid foot cannot. Tight inflexible feet need shock absorption and usually require flexible orthotics and soft-tissue supplements to absorb shock.
- Toe positions- toe positions can reveal biomechanical defects. For instance; crowded claw toes are seen often in flexible forefoot valgus and flexible plantarflexed 1st ray deformities. Hammer toes are usually present in rigid forefoot valgus and rigid plantarflexed 1st ray deformities. An HAV deformity is seen with rearfoot varus and forefoot varus deformities.
- Gait Pattern- Gait Pattern is important especially in treating children. Degree of compensation can be obtained. Rearfoot varus and forefoot varus is more consistently seen in out-toed gait; forefoot valgus more often seen in straight to in-toed gait. Early heel-off may require bilateral heel raises.
- Limb length difference- shortages greater than 1/2″ are very often the reason why some patients show more deformity in one foot than in the other and can also be responsible for back pain. Heel raises of up to 1/4″ can result in marked difference in orthotic efficacy.
- Range of motion
- Subtalar joint- important in determining how much control a patient can handle. Restricted range of motion will usually require low rearfoot posting and shock absorption orthotics.
- Ankle dorsiflexion- inability to dorsiflex to 10 degrees will require compensation through excessive pronation. Also with children and sports medicine, patients may do better with bilateral heel raises when they present with equinus.
- 1st metatarsal segment- the flexibility of the 1st metatarsal usually determines the posting system used. A flexible 1st metatarsal will easily move to the level of the 2nd metatarsal; a hypermobile will move beyond the level of the 2nd metatarsal. A hypermobile 1st metatarsal may require a 2-5 metatarsal bar with a 1st metatarsal head cutout to load the 1st metatarsal and perhaps also a 4-6 degree posting to increase the peroneus longus vector to the 1st metatarsal to increase plantarflexion to the 1st metatarsal. Rigid 1st metatarsals require low to perpendicular rearfoot posting along with decreasing the calcaneal inclination angle to achieve less plantarflexion of the 1st metatarsal. Flexible orthotics work best with this type of foot.
- Hallux dorsiflexion- to fully post a patient, good hallux dorsiflexion is needed to be able to tolerate the posting. Without good dorsiflexion, flexbile orthotics and lower posting is indicated.
- 1st metatarsal ray position- this is used to differentiate between forefoot valgus and plantarflexed 1st ray deformities which have to categories consisting of the rigid and flexible types. The applied orthotic therapy results in four different types of modules and posting systems.
- 1st metatarsal length- this is very important in determining the length of both the orthotic and the posting systems. Morton’s type feet do very well with the 1st metatarsal head cutouts. When a callus if present sub-2nd, a 2-5 metatarsal bar and 1st metatarsal head cutout can often help by transferring weight to the 1st metatarsal.
- Location of corns/calluses- plantar calluses tell a story and can confirm or deny previous examination findings. Calluses sub-1st and 5th indicate a rigid foot and calls for low rearfoot and forefoot posting, flexible orthotics and soft tissue supplements. Callus sub-2nd calls for high rearfoot posting and possible forefoot bay therapy. Calluses sub-4th ad 5th usually require high rearfoot posting. Type of callus is important in determining type of soft tissue supplement to use.
MEASUREMENTS
Measurements are very helpful but not always necessary for your orthotic manufacturer. To order orthotics based purely on measurements can be a serious mistake. They have to be considered along with all the other information.
As a general rule, the more information you provide to your orthotic manufacturing lab the better. Our qualified technicians are able to carefully create a custom instrument for your patient based on a variety of factors and data, including the important information provided on your prescription form.
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