Many nonoperative techniques exist to alleviate pain in unicompartmental osteoarthritic knees including physical therapy, heel wedges and off-loading knee braces [1]. Arthritic knee braces are particularly effective since they can be used on a regular basis at home, work, etc. Previous knee brace studies focused on their ability to stabilize anterior cruciate ligament (ACL) deficient knees. A standard technique for analyzing brace effectiveness is the use of an athrometer to look at the range-of-motion. Although this is helpful, it is more useful to use X-ray or fluoroscopy techniques to analyze the in vivo 3-D conditions of the femur and tibia. One method for doing this is Roentgen Steroephotogrammetric Analysis, which uses a calibration object and two static X-rays to perform 3-D registration of the femur and tibia. This technique is limited to static and typically non-weight bearing analysis.

We have analyzed five patients with moderate to severe osteoarthritis in both step up and step down activities with two different knee braces and also without a knee brace. Fluoroscopy of the five patients performing these activities was obtained as well as a CT scan of the knee joint for each patient. 3-D models of the femur and tibia were obtained from manual segmentation and overlaid to the fluoroscopy images using a novel 3-D to 2-D registration method [2]. This allowed analysis of 3-D in vivo weight bearing conditions. This work builds off of an analysis where 15 patients were analyzed in vivo during gait with and without knee braces [3].

All five patients experienced substantially less pain when performing the step up and step down activities with a knee brace versus without a knee brace. It should be noted that none of the five patients were obese, which can limit brace effectiveness. Preliminary results show that medial condyle separation was increased by 1.4–1.6 mm when using a knee brace versus not using a knee brace during the heel-strike and 33% phases of step up and step down activities. Also, the condylar separation angle was reduced by an average of 1.5–2.5°. Finally, consistently less condylar separation was seen during step down versus step up activities (0.5–1 mm), which can be attributed to a greater initial impact force on the knee joint during step down versus step up activities.