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.    Accordingly, one can determine the muscle(s) involved in the equinus deformity. If the dorsiflexion is poor with the knee straight and bent, there is an Achilles equinus as both muscles are tight. However, if there is improved and adequate range of motion with the knee bent, the problem is associated with a gastrocnemius equinus and the soleus, and one does not need to perform an Achilles tendon lengthening.    This is a critical distinction in the diagnostic workup. Gastrocnemius lengthening, or recession as it is also called, is safer and simpler to perform without the risk of overlengthening in comparison to Achilles tendon lengthening. However, if there is a true Achilles tendon tightness and the surgeon only lengthens the gastrocnemius portion, there will still be a clinical equinus.    Secondary clinical findings are wide and varied. The most common findings I associate with an equinus — and that I am fairly comfortable relating in part to an equinus — include plantar fasciitis, posterior tibial tendonitis or tear, retrocalcaneal exostosis, plantar plate overload and metatarsalgia, neuroma pain, hallux valgus, midfoot arthritis/Charcot and arch collapse, and diabetic foot ulceration of the midfoot and forefoot.    Potential additional secondary findings include: medial ankle synovitis and spurring; flexor hallucis tenosynovitis; sinus tarsi syndrome and synovitis; tailor’s bunion deformity and Achilles tendonitis. Although it may be common to consider Achilles tendon pain a complication of an equinus, for some reason, there is a limited number of patients diagnosed with an Achilles pathology as compared to other foot and ankle pathology related to an equinus.

A Guide To Conservative Care

The treatments for foot and ankle equinus are quite simple. After noting the underlying cause of the equinus and differentiating between gastrocnemius equinus and Achilles equinus, one can initiate a treatment plan. In mild to moderate cases, initiate a comprehensive stretching program. This includes stretching of the entire posterior compartment including the hamstring muscles, gastrocnemius muscle, soleus muscle and Achilles tendon.    We have noted in our research that a 20 percent increase in range of motion is possible with proper and constant stretching in children and adolescents. Yet only a 10 percent increase in motion is possible in adults. It is truly amazing, however, to note the level of pain decrease in an adult with a 10 percent increase in posterior muscle group motion.    If conservative stretching does not help, one may initiate a dynamic stretching treatment. This is often done through the use of a dynamic splint device. We prefer to use the Dynasplint device (Dynasplint Systems) and find that it is fairly easy for patients to dial in a dorsiflexion pressure and use the device at night. Unfortunately, this is for limited time use and patients often return to baseline levels after they cease using the device. In a small percentage of cases, continued manual stretching will help decrease the intensity/level of recurrent equinus pain.

Exploring The Surgical Options

In cases that fail conservative care and in severe cases, a surgical lengthening of the posterior muscle/tendon group(s) may be required. Again, this is the point at which it is essential to differentiate the Achilles equinus from a gastrocnemius equinus. In a gastrocnemius equinus, which we see in the majority of cases with adults and to a lesser degree in children, the procedure of choice is a gastrocnemius recession. One can perform this through a mini-incision or open slide technique. Our preferred technique is an endoscopic procedure through a 1 cm medial incision. Surgeons can perform the procedure with the patient in a supine position, negating the need for a patient flip during the case.    The endoscopic technique utilizes a surgical blade mounted on the end of a 4.0 arthroscope. Open the tendon sheath and place a cannula and trochar. Remove the trochar and insert the camera without the blade to check the position. After achieving the ideal position, mount the blade and perform a transverse lengthening of the tendon at the muscle/tendon junction. Keep the patient non-weightbearing for two weeks and keep him or her in a weightbearing boot for an additional two to three weeks unless other procedures dictate otherwise.    If an Achilles tendon lengthening is required, my approach is age dependent. In children and adolescents, I will often perform an open procedure to allow for adequate and controlled lengthening. In adults and all patients with diabetes, I will perform a three incision, percutaneous lengthening. This allows for less scarring and better aesthetics. It is essential not to overlengthen the Achilles tendon or weakness and a calcaneal gait may develop.

In Conclusion

Through proper planning, the treatment of an underlying equinus deformity has helped us relieve many of our patients’ problems with improved rates of success. I believe it is an essential part of any treatment to consider an equinus deformity as a contributing cause to foot and ankle pain. I have used the aforementioned procedures extensively in my practice and believe that the single most common cause of foot pain is often related to an equinus deformity. Dr. Baravarian is the Co-Director of the Foot and Ankle Institute of Santa Monica. He is an Associate Professor at UCLA Medical Center and is the Chief of Podiatric Surgery at the Santa Monica/UCLA Medical Center. Dr. Baravarian may be reached at bbaravarian@mednet.ucla.edu. For related articles, see “Addressing Tendon Balancing Concerns In Diabetic Patients” in the March 2003 issue of Podiatry Today.