Introduction: Biomechanical studies have frequently shown a close relationship between the knee and ankle joint movements. ACL-deficiency may change the foot pressure pattern of the ACL-deficient knee subjects. The current study aimed to investigate the pattern of the foot pressure in coper and non-coper ACL-deficient knee subjects during standing on one and both feet. Methods and Materials: This case-control study was conducted on 12 coper and 12 non-coper ACL-deficient knee subjects and 25 age-sex matched healthy subjects. The subjects were tested barefoot during single and bilateral standing on the platform of a Zebris pedobarograph tool. The outcome measures included the measurements of the pressures of each part of the foot during the tests. Results: The results showed a significantly decreased total pressure only between the non-coper and control groups during double leg stance test. In terms of the forefoot pressure, a significant increased pressure was shown only in the non-coper ACL-deficient knee subjects during both single and double leg stance tests (P<0.05). In both test conditions, the coper ACL-deficient knee subjects showed forefoot and hind foot pressures very close to the control group (P>0.05). Conclusion: This study revealed marked changes following ACL-deficiency mainlyin non-coper ACL-deficient knee subjects. The increased forefoot pressure in non-coper ACL-deficient knee subjects was probably due to the forwarded line of gravity in these patients aligned with their base of support to keep their knees more stable. Further studies are needed to verify the differences between the male and female ACL-deficient knee subjects.Keywords: Coper/non-coper ACL-deficient knee subjects; Stability; Pedobarograph; Foot pressure system; Postural contro
