Key Insights On The Role Of Equinus In Foot Pain
There has been a great deal of debate over the years about the potential cause of foot pain being associated with tightness and decreased dorsiflexion motion at the ankle due to an equinus deformity. To define equinus, we look at the horse (equine) and find that the legs are in a plantar position with what is essentially toe walking. As the term equnius has subsequently been adapted to medical pathology, it suggests the lack of dorsiflexion at the ankle due to tightness of the Achilles or gastrocnemius complex.
The main issue with such a problem has been the lack of clinical research suggesting that tightness in the posterior complex may be the cause of foot problems. There have been several publications that suggest that an equinus deformity may contribute to tendonitis, fasciitis and even forefoot ailments. However, many of these articles are subjective and lack the detailed study criteria to truly convince the research minded reader of the underlying problems of foot pain being related to an equinus deformity.
Without clinical research to guide us, we are left with equinus being a potential cause of foot problems. Much like degenerative arthritis or ankle instability may be the cause of ankle pain, in some cases, an equinus deformity may cause a collapse of the arch and medial ankle pain. Accordingly, let us take a closer look at clinical equinus, its clinical findings, potential secondary foot problems associated with an equinus deformity and the potential treatment options.
Defining Clinical Equinus
Equinus has a valgus status when it comes to foot and ankle care but is generally considered a lack of dorsiflexion of the ankle to a positive 10 degrees past neutral. One would consider neutral as the ankle at the 90-degree position in relation to the leg. However, the more important point to consider is proper foot position during an equinus test. As the foot compensates at the hindfoot and ankle for an equinus, a generalized dorsiflexion of the ankle without proper alignment of the foot will result in a false amount of abnormal dorsal motion. In other words, if the foot is allowed to pronate during dorsal motion, there is a false amount of suspected dorsal motion that is not truly present. This is due to the fact that with pronation, the foot can compensate for a lack of ankle motion.
For a true test of equinus related to the posterior muscle group without foot compensation, one should hold the foot in a rectus position or even full supination. In this way, there is no compensation at the foot and one can judge a true equinus.
Pertinent Pearls On Clinical Findings
The most common finding of an equinus deformity is an early heel off or abductory twist in gait analysis. While the patient is casually walking, the clinician will note a slight early raise of the heel at the end stage of stance as the patient begins early propulsion phase. There may also be a slight abduction of the heel at the end stage of stance to the propulsion phase to compensate for the lack of motion at the ankle level. These patients will also have a mild to moderate amount of tightness and mild pain in the gastrocnemius complex with pressure during testing. As noted above, a supinated foot in dorsiflexion will also show a lack of adequate motion at the ankle.
The most important part of the clinical workup of an equinus deformity is differentiating an Achilles equinus from an isolated gastrocnemius equinus. Podiatric physicians can do this by isolating the soleus muscle without the force of the gastrocnemius muscle. When the foot is dorsiflexed and the knee is locked straight, the soleus and gastrocnemius muscles are contracting. Yet when the knee is bent and the ankle is dorsiflexed, only the soleus is contracting.