A subluxation occurs when there is a structural insufficiency around the kneecap which leads to abnormal movement within the joint. The patella does not make proper contact with articular (or smooth) surfaces of the femur, instead it drifts medially, or laterally, and causes discomfort while grazing over bony prominences. .

Continued motion within this joint creates instances of bone-on-bone contact which trigger an inflammatory response and chronic discomfort. In the long term this continued inflammation will lead to the development of arthritis, and may contribute to further knee instability through stress on the existing structures supporting the knee. 

It is important to understand that the symptoms of this condition, at best, are managed more so than they are “cured” or rehabilitated in the traditional sense. Symptoms may be exacerbated depending on the level of stress placed on the surrounding tendons and ligaments. Excess weight, non-compliance with rest and restriction guidelines (meaning going off leash before being approved), poor nutrition, lack of appropriate medication can all contribute to how affected your pet will be by this condition. 

Your Veterinarian should be able to grade your pet’s condition within a 1 to 4 level, which corresponds to the degree of subluxation occurring at the level of the patella, or knee cap. 

​​ Grade Descriptions

  I    – Patella can be  manually displaced but immediately returns when released

  II   – Patella can be manually displaced and luxates on flexion, but is only returned by stifle extension

  III   – Patella luxates continually, but maintains enough flexibility to be manually placed

  IV   – Patella luxates continually and  scarring limits any ability to be manually placed

What Should I Look For?

You may have noticed a change in your pet’s gait pattern or activity level. Typically pets with this diagnosis  display signs of lameness that can mimic a “skipping” movement. Some pets will develop behavioral hesitancy to engage in movements that may cause this subluxation to occur, therefore you may see them hesitate to transition into sitting, or avoid jumping, resulting in an abrupt flexion of the joint. 

Many of these pets hold their hind limbs in hyperextension, or will externally rotate the limb so the knee is pointing out to the side. These are all compensatory changes that the body uses to avoid an uncomfortable sensation in the joint. While these changes can be improved by the targeted strengthening of Rehabilitation, it is impossible to alter the underlying structure without considering orthopedic surgical correction. A specialist veterinarian will indicate if you pet is a candidate for surgery. Indeed, many patients have benefitted from a pre- and post-surgical rehabilitation plan. 

For more information speak to your treating therapist. 


Lara Dellar, CCRA