‘Sticky stifles’: Diagnosis and Management

The interaction between the femoral trochleas and the patella is kept in place through the patellar ligaments that not only stabilise the sliding movement over the cranial aspect of the joint, but also allow for the stay apparatus to work and the stifle joint in extension with minimal energy usage. In order for this mechanism to disengage the ligament from the medial trochlear ridge of the femur, activity from the quadriceps muscles is needed. In normal conditions this should be an almost effortless action; however, there are four reasons why this might not be smooth and hence we see a ‘sticky stifle’: 1) failure of the muscle itself; 2) stiffness of the vastus medialis; 3) shortening of the medial patellar ligament; 4) abnormal anatomical congruency between the two bones. ‘Sticky stifle’ in this talk is used to describe cases that cannot release this mechanism with the necessary ease.

Diagnosis is based on visual observation of the mechanical lameness, palpation and ultrasonography and, although it is fairly straightforward in severe cases, it can be trickier in intermittent cases during exercise.

Treatment options are varied and range from the radical surgery of desmotomy to less invasive procedures of ligament splitting and injection of caustic agents to promote fibrosis and shorten the ligament, as well as hormone therapies that may lead to ligament and muscle relaxation. None of these should be preferred to adequate physiotherapy, shoeing and a good exercise plan as this should resolve the majority of cases without the downsides of surgery. Understanding the primary mechanism behind the pathology will aid in selecting the appropriate treatment.

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