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Understanding Patella Luxation

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TaBle of Contents
Overview
Causes And Symptoms
Types of Patella Luxation
Symptoms and Clinical Presentation
Diagnosis & Treatment
Diagnosis
Treatment Options
Prognosis and Long-Term Management
Possible concurrent joint abnormalities
Tibial Tuberosity Transposition (TTT) Technique

Patella luxation, also known as kneecap dislocation, is a common orthopedic condition in both dogs and cats. 

Overview

Patella luxation occurs when the kneecap (patella) moves out of its normal position within the groove of the thigh bone (femur). This displacement can lead to pain, lameness, and reduced mobility in affected animals. Timely and effective surgical intervention is crucial to improve their quality of life and prevent long-term complications.
In this video you see a typical pre surgery walk with a patellar luxation:

Causes And Symptoms

Contributing factors, types, and signs of patella luxation

Certain factors increase the likelihood of developing patella luxation:
  • Genetic predisposition: Small and toy breeds are more commonly affected, with some studies reporting prevalence rates of up to 7% in certain breeds.
  • Genetic factors: Inherited abnormalities in the anatomy of the knee joint contribute to the development of patella luxation.
  • Trauma or injury: Acute trauma or repetitive stress to the knee joint can cause patella luxation, particularly in active animals.
  • Age and weight: Young and overweight animals are at higher risk due to increased stress on the joints.

Types of Patella Luxation

Patella luxation can be classified based on its direction and severity:
  • Medial luxation: The patella moves towards the inside of the knee joint.
  • Lateral luxation: The patella moves towards the outside of the knee joint.
  • Grade 1: Occasional luxation that can be manually corrected. However, it takes its natural position again after the patella is released.
  • Grade 2: Frequent luxation that spontaneously corrects or can be easily manipulated back into place.
  • Grade 3: Persistent luxation that requires manual manipulation to correct.
  • Grade 4: Permanent luxation where the patella remains dislocated with up to 90° of rotation of the proximal tibial plateau.
Above image is attributed to the article Patellar luxation in dogs by Di Dona et al., which is published and licensed by Dove Medical Press Limited

Symptoms and Clinical Presentation

Signs of patella luxation may vary depending on the severity and chronicity of the condition:
  • Intermittent lameness: Animals may exhibit limping or favoring of the affected limb, particularly after physical activity.
  • Skipping or hopping: Some pets may skip or hop while walking due to discomfort.
  • Reluctance to bear weight: Animals may avoid putting weight on the affected limb.
  • Swelling and joint instability: In severe cases, swelling and joint instability may be evident.
Image by Filip Kruchlik on Pixabay

Diagnosis & Treatment

Assessment and management of patella luxation

Clinical assessment, diagnosis, classification, and grading of patella luxation enable accurate diagnosis, guide treatment selection, serve as prognostic indicators, and facilitate monitoring of treatment outcomes.

Diagnosis

A thorough physical examination and diagnostic imaging are essential for diagnosing patella luxation:
  • Palpation and Gait Analysis: Palpation of the knee joint is crucial to determine the position and mobility of the patella. Gait analysis helps identify any abnormalities in the animal's walking pattern, such as skipping, hopping, or lameness.
  • Range of Motion Assessment: Assessing the range of motion of the affected limb aids in evaluating joint stability and detecting any restrictions or abnormalities.
  • Diagnostic Imaging: Radiography is the primary imaging modality used to confirm the diagnosis and assess the severity of patella luxation. Additional imaging modalities such as MRI or CT scans may be employed to evaluate soft tissue structures and identify concurrent joint abnormalities.
Classification and grading of patella luxation are crucial in determining the most appropriate treatment approach. Conservative management may be suitable for lower-grade luxations, while higher-grade luxations are associated with increased risk of complications and may require more extensive surgical interventions.

Treatment Options

Treatment for patella luxation depends on the severity of the condition and the presence of concurrent joint abnormalities:
  • Conservative management: Grade 1 and Grade 2 luxations may be managed conservatively with rest, anti-inflammatory medications, and physical therapy.
  • Surgical intervention: Grade 3 and Grade 4 luxations often require surgical correction to realign the patella and stabilize the knee joint. Surgical techniques may include trochleoplasty, tibial tuberosity transposition, and soft tissue reconstruction.
  • Rehabilitation: Physical therapy and rehabilitation exercises play a crucial role in improving joint function, reducing pain, and promoting recovery following surgical intervention.
Example of a surgical intervention using a tibial tuberosity transposition technique. Image courtesy of Dr. Luca Petagna.

Prognosis and Long-Term Management

The prognosis for patella luxation varies depending on the severity of the condition, the presence of concurrent joint abnormalities, and the success of treatment:
  • Early diagnosis and appropriate treatment significantly improve the long-term prognosis.
  • Close monitoring and regular veterinary examinations are essential to detect and manage potential complications, such as osteoarthritis and recurrent luxation.
  • Weight management, regular exercise, and joint supplements may help support joint health and reduce the risk of recurrence.

Possible concurrent joint abnormalities

Several concurrent joint abnormalities may coexist with patella luxation in dogs and cats, including:
Cruciate Ligament Injury:
  • Cranial cruciate ligament (CrCL) rupture is a common concurrent condition, particularly in dogs.
  • The instability resulting from a CrCL tear can exacerbate patella luxation and vice versa, leading to lameness and joint dysfunction.
 See how you can treat a Patella Luxation and a concomitant CrCL rupture
Meniscal Tears:
  • Meniscal tears refer to injuries involving the fibrocartilaginous structures located within the knee joint, known as menisci. These tears often accompany CrCL rupture and commonly occur concurrently with patella luxation.
  • These tears may exacerbate lameness and further compromise joint function.
Hip Dysplasia:
  • Hip dysplasia is a developmental abnormality characterized by malformation of the hip joint.
  • Animals with hip dysplasia may exhibit altered gait patterns and joint instability, which can exacerbate symptoms of patella luxation.
 Read more about Hip Dysplasia & our new 3D HIP
Osteoarthritis:
  • Chronic joint instability resulting from patella luxation and concurrent abnormalities can lead to secondary osteoarthritis.
  • Osteoarthritis causes progressive joint degeneration, resulting in pain, stiffness, and reduced mobility.
Trochlear Groove Abnormalities:
  • Anatomical abnormalities in the trochlear groove, where the patella articulates with the femur, can predispose animals to patella luxation.
  • Shallow or malformed trochlear grooves may contribute to patella instability and increase the risk of luxation.
Patellar Ligament Abnormalities:
  • Anomalies in the patellar ligament, such as laxity or contracture, can affect patellar tracking and stability within the femoral groove.
  • These abnormalities may predispose animals to patella luxation or contribute to its persistence.
Joint Congruency and Alignment Issues:
  • Malalignment or incongruence of the joint surfaces within the knee joint can predispose animals to patella luxation and exacerbate symptoms.
  • Structural abnormalities in the bones or joint capsules may contribute to joint instability and compromise joint function.
Soft Tissue Abnormalities:
  • Abnormalities in the soft tissues surrounding the knee joint, such as ligament laxity or muscle weakness, can contribute to joint instability and exacerbate patella luxation.
Musculoskeletal Trauma:
  • Previous musculoskeletal injuries or trauma, such as fractures or dislocations, can result in altered joint biomechanics and predispose animals to patella luxation and associated abnormalities.

Tibial Tuberosity Transposition (TTT) Technique

with the RAPID Patella Luxation System

Tibial Tuberosity Transposition (TTT) is a surgical technique commonly used to correct patellar luxation, particularly in cases where conservative management has failed or in severe cases of luxation. TTT involves the transposition of the tibial tuberosity, the bony prominence where the patellar ligament attaches, to a new position on the tibia. The surgeon makes an incision over the tibial tuberosity and creates a bone cut (osteotomy) to detach the tuberosity from its original location. The tuberosity is then repositioned laterally or medially, depending on the direction of the patellar luxation, to realign the patella within the femoral groove. The tuberosity is secured in its new position using specialized implants such as plates, screws, or wires to maintain stability. By repositioning the tibial tuberosity, TTT alters the biomechanics of the knee joint, redistributing forces and stabilizing the patella during movement. 
Our RAPID Patella Luxation Plating System was designed and developed specifically to correct a patella luxation. Taking inspiration from the front plate design of our TTA RAPID® Cages, the RAPID Luxation Plates feature multiple screw fixation points and come in three different sizes. Specialized instrumentation, such as the uniquely designed RAPID Luxation Tibia Tappet, allows for a controlled transposition of the tibial tuberosity, enabling the surgeon to achieve the desired degree of alignment safely and accurately.
 Learn more about the RAPID Patella Luxation Technique

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