High Kneecap Syndrome (Patella Alta): Causes, Symptoms, Diagnosis, and Treatment

What is a High Kneecap Syndrome?

Patella alta, commonly known as "high kneecap syndrome," is an anatomical condition where the patella (kneecap) sits abnormally high in its groove on the femur, leading to altered knee joint mechanics and an increased susceptibility to pain and instability.

Understanding Patella Alta

Patella alta, derived from Latin meaning "high patella," describes a specific anatomical variant of the patellofemoral joint. In this condition, the patella is positioned superiorly (higher) relative to the femoral trochlear groove, the V-shaped indentation on the end of the thigh bone where the patella normally glides during knee movement. This elevated position means the patella does not engage properly with the trochlear groove, especially in the initial degrees of knee flexion. This altered engagement can significantly impact the biomechanical function of the quadriceps muscle group and lead to a range of issues, from chronic pain to recurrent dislocations.

Anatomy and Biomechanics of the Knee

To understand patella alta, it's essential to grasp the normal anatomy and biomechanics of the patellofemoral joint. The patella acts as a sesamoid bone, embedded within the quadriceps tendon, which connects the powerful quadriceps muscles to the tibia via the patellar ligament. Its primary role is to increase the mechanical advantage (lever arm) of the quadriceps, making knee extension more efficient.

Normally, as the knee flexes, the patella smoothly tracks within the trochlear groove. This tracking is influenced by the balanced pull of the quadriceps muscles, the integrity of surrounding ligaments (like the medial patellofemoral ligament, MPFL), and the shape of the trochlear groove itself. In patella alta, the superior position of the patella means it may not fully seat within the trochlear groove until the knee is significantly flexed. This can lead to:

• Reduced Contact Area: Less surface contact between the patella and femur, increasing stress on a smaller area of cartilage.
• Altered Tracking: The patella may track laterally (to the outside) or tilt, causing friction and irritation.
• Decreased Quadriceps Efficiency: The altered lever arm can reduce the effective force production of the quadriceps.

Causes and Risk Factors

Patella alta can be congenital (present from birth) or acquired due to various factors:

• Congenital/Developmental:
  • Genetics: An inherited predisposition to longer patellar tendons or a shallower trochlear groove.
  • Growth Plate Anomalies: Disturbances during bone growth in childhood or adolescence.
• Acquired Factors:
  • Trauma: Severe injuries, such as a patellar tendon rupture, or surgical repair of such injuries, can sometimes lead to an altered patellar position if the tendon heals in a shortened or lengthened state.
  • Muscular Imbalances:
    • Tight Quadriceps: Particularly the rectus femoris, which originates from the hip and crosses the knee, can exert an excessive superior pull on the patella.
    • Weak Vastus Medialis Obliquus (VMO): The VMO is crucial for medial stabilization of the patella. Weakness can allow the patella to be pulled laterally and superiorly.
    • Tight Hamstrings/Gastrocnemius: While not directly pulling the patella, tightness in these posterior leg muscles can alter overall knee kinematics and contribute to anterior knee pain patterns that may exacerbate patella alta symptoms.
  • Ligamentous Laxity: General hypermobility of joints can contribute to patellar instability, which is often associated with patella alta.
  • Overuse and Chronic Stress: Repetitive activities involving jumping or deep knee flexion can place excessive stress on the patellofemoral joint, potentially leading to adaptive changes or symptoms that mimic patella alta.

Common Symptoms

The symptoms of patella alta often revolve around anterior knee pain and instability. They typically worsen with activities that load the knee joint:

• Anterior Knee Pain: This is the most common symptom, usually felt around or behind the kneecap. It's often aggravated by:
  • Stair climbing (especially going down)
  • Squatting or lunging
  • Jumping or landing activities
  • Prolonged sitting with flexed knees ("theater sign")
• Patellar Instability or Subluxation: A feeling that the kneecap is shifting, giving way, or partially dislocating, particularly with twisting movements or sudden changes in direction. In severe cases, full dislocations can occur.
• Clicking, Popping, or Grinding Sensations: These sounds (crepitus) can occur during knee movement due to abnormal tracking or cartilage irritation.
• Difficulty with Deep Knee Flexion: The altered patellar position can make it difficult or painful to fully bend the knee.
• Visible High Position of the Kneecap: In some individuals, the patella may appear visibly higher than normal when the leg is extended.
• Quadriceps Weakness or Inhibition: Pain and altered mechanics can lead to disuse atrophy or difficulty recruiting the quadriceps muscles effectively.

Diagnosis

Diagnosing patella alta involves a combination of clinical examination and imaging studies:

• Clinical Examination: A physical therapist or orthopedic surgeon will assess your knee for:
  • Patellar Position: Observing the kneecap's resting position.
  • Patellar Mobility: Assessing how easily the kneecap moves side-to-side and up-and-down.
  • Range of Motion: Checking the knee's flexibility.
  • Muscle Strength and Balance: Evaluating the strength of the quadriceps, hamstrings, glutes, and core.
  • Patellar Tracking: Observing how the kneecap moves during knee flexion and extension.
  • Special Tests: Performing specific tests to assess for instability or pain patterns.
• Imaging Studies:
  • X-rays: A lateral view of the knee is crucial. Specific measurements (e.g., Insall-Salvati ratio, Blackburne-Peel ratio, Caton-Deschamps index) are used to quantify the patellar height relative to the femur. A ratio greater than the normal range indicates patella alta.
  • Magnetic Resonance Imaging (MRI): Provides detailed images of soft tissues, including cartilage, ligaments, and tendons. It can help identify associated conditions like chondromalacia (cartilage softening), patellar tendinopathy, or ligamentous tears that may contribute to symptoms or instability.
  • Computed Tomography (CT) Scan: Less common for diagnosing patella alta itself but can be used for detailed assessment of bone morphology, including trochlear dysplasia (a shallow trochlear groove) which often co-occurs with patella alta.

Treatment and Management Strategies

Treatment for patella alta typically begins with conservative approaches, focusing on symptom management and improving knee mechanics. Surgical intervention is considered for severe cases, especially those with recurrent instability or persistent pain despite extensive conservative efforts.

Conservative Management

The cornerstone of conservative treatment is physical therapy:

• Pain and Inflammation Management:
  • Rest and Activity Modification: Avoiding activities that aggravate pain.
  • Ice and Heat Therapy: To reduce swelling and discomfort.
  • Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): To manage pain and inflammation (under medical guidance).
• Physical Therapy:
  • Strengthening Exercises: Focus on strengthening the vastus medialis obliquus (VMO) to improve medial patellar pull, as well as gluteal muscles (gluteus medius and maximus) and core stabilizers to improve lower limb alignment and control.
  • Stretching and Flexibility: Addressing tightness in the quadriceps (especially rectus femoris), hamstrings, hip flexors, and IT band to reduce abnormal pulling forces on the patella.
  • Patellar Taping or Bracing: Kinesiology tape or specialized patellar braces can help improve patellar tracking and provide support, reducing pain during activity.
  • Manual Therapy: Techniques like soft tissue mobilization and joint mobilizations may be used to address restrictions and improve tissue extensibility.
  • Neuromuscular Re-education: Training to improve proprioception (joint awareness) and control of movement patterns, especially during activities like squatting, lunging, and jumping.

Surgical Intervention

Surgery is typically reserved for individuals with persistent patellofemoral pain and/or recurrent patellar dislocations that do not respond to conservative management. The goal of surgery is to lower the patella and/or improve its stability and tracking.

• Tibial Tubercle Osteotomy (TTO): This is a common procedure where a section of the tibia (shin bone) where the patellar tendon attaches (the tibial tubercle) is cut and repositioned distally (downwards) and sometimes medially (inwards) to effectively lower the patella and improve its tracking in the trochlear groove.
• Medial Patellofemoral Ligament (MPFL) Reconstruction: Often performed in conjunction with a TTO, this procedure reconstructs the MPFL, a key ligament that helps prevent the patella from dislocating laterally.

Rehabilitation and Prevention

Following a surgical procedure, a structured rehabilitation program is crucial for optimal recovery. For conservative management, ongoing commitment to exercises is key for long-term symptom control and prevention of recurrence.

• Progressive Strengthening: Continue to build strength in the quadriceps (with emphasis on VMO), glutes, and core.
• Flexibility and Mobility: Regularly stretch to maintain optimal muscle length and joint range of motion.
• Proprioception and Balance Training: Incorporate exercises that challenge balance and joint awareness to improve stability and control during dynamic movements.
• Biomechanics Education: Learn and practice proper movement mechanics for daily activities, sports, and exercise (e.g., proper squat form, landing mechanics for jumping).
• Gradual Return to Activity: Avoid returning to high-impact or aggravating activities too quickly. Progress should be slow and guided by pain levels and functional improvement.

When to Seek Medical Attention

It's advisable to consult a healthcare professional, such as an orthopedic surgeon or physical therapist, if you experience:

• Persistent knee pain that doesn't improve with rest or basic self-care.
• Recurrent episodes of your kneecap feeling unstable, shifting, or dislocating.
• Significant swelling, warmth, or redness around your knee.
• Inability to bear weight on your leg or walk normally.
• Symptoms that worsen over time or interfere with daily activities and quality of life.

Early diagnosis and appropriate management are crucial for individuals with patella alta to prevent further joint damage and improve long-term knee function.