Ankle inversion sprain is a common injury that can cause joint stiffness and range of motion deficits.(Holmer 1994, Beynnon 2001, Denegar 2002, Green 2001) Subtalar joint manipulation has been advocated as an intervention for inversion sprains to reduce pain, decrease joint stiffness, and improve range of motion.(Lopez-Rodriguez 2007)~The ankle is comprised of the talocrural and subtalar joints and their respective joint axes.(Hubbard 2006) Ankle rotation about these axes can be parameterized using quaternions, a four dimensional unit vector. Range of motion (ROM) about these axes can be determined by performing an eigen analysis of the quaternion matrices to determine the root mean squared values of the motion data about these axes.~The objective of the study is to investigate the immediate effects of subtalar joint manipulation on the ROM about the ankle's talocrural and subtalar joints on ankles that have sustained a subacute, grade II inversion sprain.~Forty patients with one sprained ankle and one asymptomatic ankle will be recruited. The subjects will be randomized into either a subtalar manipulation group or a sham manipulation group. The sprained ankle of each patient will receive either a standardized subtalar joint manipulation or a sham manipulation. The same patient's asymptomatic ankle will serve as the non-treatment control group. Range of motion pre- and post-manipulation will be quantified utilizing a quaternion eigen analysis. Kinematic and kinetic parameters will be collected during the manipulation to biomechanically characterize the manipulation. Pain pressure threshold and visual analog scale measurements for pain, stiffness, and quality of movement will be collected.~Our primary hypothesis is subtalar joint manipulation will increase subtalar ROM, but will have no effect on talocrural ROM. Our secondary hypothesis is subtalar joint manipulation will have positive effects on pain, stiffness, and quality of movement.
The purpose of the study is to determine whether manipulation of the subtalar joint (one of the two joints of the ankle) has an effect on ankle range of motion in a group of ankles that have sustained a subacute inversion ankle sprain.~The investigators expect subtalar joint manipulation will increase ankle range of motion about the subtalar joint, but not at the talocrural joint (the other joint of the ankle).