The question of whether to place a new foot insert over or instead of the existing shoe lining is a common point of confusion. The terms “orthotic” and “insole” are frequently used interchangeably, muddling the understanding of their function and proper use. The correct protocol for using these inserts depends entirely on the fundamental differences in their design and purpose, especially when addressing foot pain or seeking better biomechanical alignment.
Understanding the Difference Between Orthotics and Insoles
Standard insoles are mass-produced liners designed primarily for comfort, cushioning, and generic shock absorption. These inserts are typically made from soft materials like foam, gel, or thin fabric and provide an accommodative layer inside the shoe. Their main function is to enhance the wearer’s immediate comfort or manage moisture and odor, not to correct specific foot or gait abnormalities.
Orthotics, by contrast, are medical-grade devices engineered to correct abnormal foot function and address biomechanical issues such as overpronation or supination. Custom orthotics are made from a three-dimensional mold or scan of an individual’s foot, ensuring a precise fit and targeted functional control. Even high-grade over-the-counter orthotics feature a semi-rigid shell designed to provide structural support to the arches and heel. The defining distinction is that orthotics are functional and corrective, while insoles are generally accommodative and comfort-based.
The Standard Placement Rule: Why Orthotics Replace Insoles
In nearly all situations, a functional orthotic must replace the factory insole already present in the shoe. The orthotic is designed to interact directly with the rigid structure of the shoe’s sole, known as the lasting board, to achieve its corrective function. This direct contact ensures the orthotic’s stabilizing angles and support contours are fully engaged to control foot motion.
The process for proper installation is straightforward: the existing removable liner, which is the soft factory insole, must be taken out of the shoe first. Most modern footwear, especially athletic and walking shoes, includes a removable liner that easily lifts out. The orthotic is then placed directly onto the exposed shoe bed, fitting snugly against the interior walls of the footwear.
This replacement protocol is necessary because the effectiveness of the orthotic relies on its intended positioning within the shoe’s volume. An orthotic is engineered to manage the forces that pass through the foot during walking or running by controlling the heel and arch. If the orthotic is placed correctly, it ensures the foot lands in the device’s heel cup, stabilizing the rearfoot and controlling abnormal motion.
The precise contouring and posting, which are the corrective angles built into the orthotic, must be anchored against a non-yielding surface. By sitting flush against the firm shoe bed, the orthotic’s biomechanical features can effectively influence the foot’s position and movement. This maximizes the device’s ability to distribute pressure and support the three arches of the foot.
Biomechanical Consequences of Stacking Footwear Inserts
Placing an orthotic on top of the original insole compromises the device’s ability to function as intended, often negating its corrective purpose. The soft, compressible material of the standard insole acts as a buffer, preventing the rigid orthotic shell from controlling the foot’s motion. This stacking essentially floats the orthotic, allowing the foot to sink into the cushioning rather than being firmly supported by the device’s structure.
This improper layering leads to several adverse biomechanical effects, primarily introducing instability. The combined thickness of the two inserts raises the foot higher within the shoe, which can cause the heel to slip out and create friction, increasing the risk of blisters. Furthermore, the elevated position reduces the available space in the toe box, leading to excessive pressure on the toes and forefoot.
Crucially, placing the orthotic on a soft surface causes the orthotic’s corrective angles to be absorbed and distorted. The device cannot achieve the precise alignment of the foot and ankle it was prescribed for, potentially worsening conditions like overpronation or supination. The result is a device that offers general cushioning instead of targeted functional support, which can exacerbate existing pain points or create new ones due to poor foot positioning.