What is Patella Luxation (PL)? 

Patella instability or luxation (dislocation), is caused by malalignment of the quadriceps mechanism, due to the shape of the hindlimb. Generally, the changes that result in PL occur during early growth and development and are focused around the stifle joint (knee). If the patella is not tracking normally within the trochlear groove of the femur (thigh bone), this groove may not develop normally. Further, the cartilage of the patella and trochlear ridges may erode over time due to repeated luxation, leading to arthritis. 

​

Lameness in dogs with PL is generally due to the abnormal function of the leg, causing a characteristic "skipping" gait. Severe cases may instead show excessive inward rotation and limited extension of the knee, without an obvious skip. In some cases, pain due to stress on the surrounding tissues and cartilage wear may also contribute.

 

Treatment of Patella Luxation:

Many dogs maintain a relatively good quality of life with PL. If mobility is affected significantly, however, surgical correction is recommended, particularly if high-levels of activity are desired.

​

The goal of surgical correction is to restore more normal patella tracking, improving the function of the stifle throughout life. 

​

What is involved in correction of Patella Luxation? 

Dogs come in all different shapes and sizes, but common patterns of shape deviations in the femur and tibia can be identified, usually on radiographs.

​

This variability in the shape of each patient means each one requires an individualised assessment and plan. This plan aims to correct the alignment of the patella and may also restore trochlear groove depth and alteration of the surrounding soft-tissues to support the repair. Repairs may be relatively simple or involve more complex corrections.

 

Some patients develop with bowed femurs, which forms a major component of the deformities contributing to PL. In these cases, restoring a normal curve to the femur provides a very reliable correction and forms the cornerstone of the repair. This involves cutting the femur (distal femoral osteotomy - DFO), removing a wedge of bone and realigning the bones to straighten the patella mechanism. The bone is fixed in its new position with a plate and screws.  

​​

Prognosis:

The prognosis following surgical correction of PL is good or very good in most patients - most will return to good function approximately 2-3 months following surgery, but cases with higher grade luxation and more severe secondary changes (soft tissue and osteoarthritis) may do less predictably well.

 

Recurrence of PL is dependent on the underlying abnormalities and the corrective techniques used, highlighting the importance of individual assessment.

​