Ability to Show the Knuckles in Forefoot Helps to Assess Intrinsic Muscle Function

Abstract

Category:Midfoot/Forefoot; Lesser ToesIntroduction/Purpose:The plantar plate stabilizes the metatarsophalangeal joint (MTPJ). When the plantar plate is disrupted the static forces resisting the strong extensor muscles are compromised, overwhelming the intrinsic muscles of the foot resulting in toe deformities. The proposed ‘knuckle test’ is a clinical exam to evaluate for intrinsic muscle weakness. Patients with negative knuckle tests are unable to plantar flex their toes at the MTPJ to prominently display the knuckles. This study seeks to determine the prevalence of negative knuckle tests in patients with and without associated toe deformities.Methods:This is an observational case-control study to compare the prevalence of a negative knuckle test in participants with evidence of toe deformities or plantar plate incompetence based on physical exam findings (case group) to participants with normal feet (control group), defined as no signs or symptoms of a current or past plantar plate tear. A participant will qualify for the case group if they have a positive MTPJ drawer test or an associated toe deformity (medial deviation, hyperextension of the MTPJ, floating toe, hammer toe deformity, or crossover toe). The participants will also complete a short survey to identify factors associated with plantar plate injuries such as BMI, gender, age, smoking history, diabetes, sports history, injury history, heel or boot wear, hyper flexibility, and collagen disorders.Results:The research team has gathered 75% of the participant data. Preliminary data shows that the majority of participants in both groups have negative knuckle tests. The final results will be analyzed once all the data has been collected.Conclusion:The percentage of negative knuckle test in patients without toe abnormalities or symptoms was unexpectedly high. The implication is that there is a high incidence of weak intrinsic foot muscles. Foot intrinsic muscle exercises may help to prevent toe deformities. Other findings will be interpreted after all data has been collected.