What is ‘intermittent upward patellar fixation’?
Although patellar fixation is normal in the standing horse, it can produce pelvic limb dysfunction if it occurs during exercise. Inadvertent locking of the patella over the medial femoral trochlea prevents normal flexion of the affected limb(s). Consequently, pelvic limb asymmetry and lameness frequently become evident. What causes upward patellar fixation? There are 3 primary causes of upward patellar fixation in the horse: Lack of fitness: Lack of quadriceps and/or biceps femoris muscle tone results in an inability to quickly pull the patella up and off of the medial femoral trochlea. Straight or upright pelvic limb conformation: This places the medial femoral trochlea further distad in closer proximity with the patella, facilitating patellar fixation. Excessive distal patellar ligament length: This places the patella proximad in closer proximity with the medial femoral trochlea, where it can inadvertently “catch” or “lock” It should be noted that the factors which cause upward patel
