Diagnosis

Patellar luxation is one of the most common orthopedic conditions in dogs, diagnosed in 7% of puppies. While the condition primarily affects small breeds, several large breeds, such as Great Pyrenees and Flat-coated Retrievers are also considered pre-disposed to the disease.

In a normal limb, the patella or “knee cap” is located deep in the quadriceps muscles of the thigh and glides in the groove of femur at the knee joint. From the quadriceps, the patella is then attached to the crest of the tibia, just below the knee, by a tendon. The quadriceps muscle, the patella and its tendon form the “extensor mechanism” and are normally well-aligned with each other.

When the extensor mechanism is not aligned, the patella rides outside the groove of the femur, a condition called Patellar Luxation. Luxation is the medical term for dislocation. When the patella dislocates to the outer aspect of the knee, away from the spine, it is called lateral patellar luxation (LPL). And when the patella dislocates inwardly, toward the spine, it is considered a medial patellar luxation (MPL).

While the cause of patellar luxation can be traumatic, the specific cause of patellar luxation for the vast majority of patients is unclear and influenced by combinations of congenital and developmental factors. The condition is not merely a problem of the knee but the entire extensor mechanism.

To understand the full scope of the malalignment, a comprehensive radiographic and physical is exam are needed to understand the impact each bone/segment is having on the overall mechanism.

Signs of Patella Luxation

Mild or moderate patellar luxation is seldom diagnosed when dogs are puppies. For most, the disease will progress slowly over time and be observed in periods of intermittent lameness, skipping and discomfort during or after physical activity.

Compensation by shifting weight to unaffected limbs, is common. This can hide the disease from pet owners for many years.

Signs of Lameness:

• Pain and stiffness
• Unwillingness to play, ascend/descend stairs
• Decreased activity
• Intermittent lameness (limping or skipping)
• Decreased range of motion
• Swelling around the patella and knee.
• Muscle atrophy (decrease in muscle mass)

If you suspect that your companion is experiencing a form of hind limb lameness, contact your veterinarian and schedule a physical exam.

Treatment Options

Patellar luxation is not expected to resolve on its own. Conservative management by improved diet, activity restriction, physical rehabilitation, non-steroidal anti-inflammatory drugs and oral supplements can help manage and mitigate the symptoms, but progression of disease and worsening of symptoms are expected.

For patients who do not respond to conservative methods, surgical treatment is recommended.

The objective of surgical treatment is to restore joint stability. Treatment strategies are dependent on a comprehensive understanding of all underlying factors.

In order to address all factors, the following surgical treatments are often performed in combinations:

• Soft tissue reconstruction around the knee cap to improve the capture of the patella
• Deepening the groove of the femur by block or wedge resection.
• Cutting and moving the tibial crest to improve the alignment of the quadriceps tendon, commonly referred to as Tibial Tuberosity Transposition (TTT)
• Address alignment by correcting a deformed femur and/or tibia. This is done by cutting the bone, correcting the abnormal bone/s and stabilizing the segments with a bone plate
• Replacing a severely diseased petallo-femoral joint by patellar groove replacement (PGR)

If you suspect that your companion is suffering from patella luxation and instability, contact your general practitioner to inquire about a physical and radiographic exam. Unique radiographs and evaluations of joint function will be performed to properly screen for all contributing factors.

Products & Solutions

Due to the wide spectrum of severity in clinical presentation and many combinations of conditions that influence the mechanics, surgical treatment for patella luxation is more challenging than many pet owners and veterinarians assume.

Veterinary surgeons who address the full spectrum of disease will have advanced training in orthopedic radiography, limb alignment evaluation, corrective osteotomies, bone plating and joint replacement.

When the disease has progressed to severe joint degeneration where the grooved portion of the femur is incapable of retaining the patella, partial joint replacement is considered.

In 2009, KYON proposed a novel Patellar Groove Replacement (PGR) prosthesis. PGR replaces the diseased trochlea with a titanium implant that addresses alignment, captures the patella and provides a gliding surface able to withstand lifelong wear.

PGR can be combined with TTA, TTA-2, TPLO and lateral suture for patients who suffer from a simultaneous cruciate ligament rupture.

For patients who require corrective osteotomies, KYON Advanced Locking Plate System (ALPS®) technology offers less iatrogenic trauma, greater versatility, increased overall stability and early fracture healing advantages for patients. The ability to contour plates in all planes and combine with other plates or implants makes ALPS the ideal system to stabilize corrective osteotomy constructs.