The amount of available range of motion (ROM) at a joint is considered to be a vital component of physical examinations and is traditionally assessed using a standard goniometer. However, standard goniometry measurements are plagued with measurement error, resulting in inconsistent measurements. For this reason clinicians have attempted to identify alterative methods of accurately assessing joint motion. Therefore, the purpose of this study was to compare the relationship between ankle plantarflexion and dorsiflexion using computer-aided lateral digital photography (CALDP) goniometry and standard goniometry measurements. Forty-seven subjects (25 males and 22 females) free of lower extremity injuries for at least six months volunteered for the study. Subjects were placed in a short sitting position. To control measurement error a polyvinyl chloride (PVC) frame was placed in front of the knees, allowing a 90° angle to be maintained. Measurements were counterbalanced to control effect bias. Ankle ROM using a standard goniometer was assessed using traditional landmarks; the center of the lateral malleolus (fulcrum), long axis of the fibula (stationary arm), and long axis of the fifth metatarsal (movable arm). Subjects were instructed to maximally flex and extend the ankle joint. Ankle ROM using CALDP was assessed by placing markers over the bony landmarks of the fibula head, center of lateral malleolus, and center of the fourth and fifth metatarsalphalangeal joints. After reaching maximal joint movement, a digital photograph of each position was recorded. Digital photos were downloaded to a laptop computer and viewed using Jasc Paint Shop Pro 6.0TM (Ottawa, Canada). Each landmark's X and Y coordinates were located by placing a crosshair devise on the center of each marker. The Law of Cosines (a2 = b2 + c2 – (2bc CosA)) – 90 was applied to calculate the angle from the digital image. The mean (SE) scores for ankle plantarflexion for standard goniometric and CALDP were 58.5° (1.3°) and 67.2° (.94°), respectively. A Pearson Product-Moment Correlation Coefficient revealed a significant relationship between ankle plantarflexion standard goniometry and CALDP, r (45) = .917, P = .000. Results suggest that CALDP goniometry for ankle plantarflexion compares well with standard goniometry measurements. Digital images of joint motion offer many advantages including, objective and consistent measurements, objective documentation for insurance purposes, and use in rehabilitation to increase patient motivation through visual imagery. However, further research is needed to examine inter-rater and intra-rater reliability and validity using CALPD at the ankle and other joints.Keyword(s): athletics/sports, measurement/evaluation, technology