Patella Alta: Understanding High Kneecaps, Causes, Symptoms, and Treatment

Why does my knee cap sit high?

A high-sitting kneecap, medically known as Patella Alta, occurs when the patella (kneecap) rests in a more superior position than normal relative to the femur (thigh bone) and tibia (shin bone), often due to an elongated patellar tendon or other anatomical variations.

Anatomy of the Patella and Patellar Tendon

To understand why a kneecap might sit high, it's crucial to first grasp the basic anatomy of the knee joint, specifically the patellofemoral joint. The patella is a sesamoid bone, meaning it's embedded within a tendon—in this case, the quadriceps tendon. It articulates with the trochlear groove at the end of the femur. Below the patella, the patellar tendon connects the patella to the tibial tuberosity, a bony prominence on the front of the tibia.

This entire extensor mechanism (quadriceps muscles, quadriceps tendon, patella, patellar tendon, and tibial tuberosity) is critical for knee extension, allowing us to straighten our leg, walk, run, and jump. The patella acts as a fulcrum, increasing the mechanical advantage of the quadriceps muscles, thereby improving the efficiency of knee extension.

Understanding Patella Alta

Patella Alta literally translates to "high kneecap." In this condition, the patella sits abnormally high in its trochlear groove, or sometimes even completely above it, especially when the knee is extended. This positioning can be determined by specific anatomical ratios measured on imaging, such as the Insall-Salvati ratio or the Blackburne-Peel ratio.

A high-riding patella can compromise the biomechanics of the knee joint. When the patella sits too high, it may not engage properly with the trochlear groove during early knee flexion (bending). This can lead to:

• Reduced contact area between the patella and femur.
• Increased contact pressure in specific areas.
• Altered tracking of the patella during movement.
• Decreased mechanical advantage of the quadriceps.

Primary Causes of Patella Alta

The reasons for a high-sitting kneecap are multifaceted, ranging from congenital factors to acquired conditions.

Developmental and Congenital Factors

Some individuals are simply born with a predisposition to patella alta. This can be due to:

• Genetics: A familial tendency for longer patellar tendons or specific knee anatomical variations.
• Growth Plate Anomalies: During skeletal development, unusual growth patterns around the knee can lead to a proportionally longer patellar tendon.
• Generalized Ligamentous Laxity: Conditions like Ehlers-Danlos syndrome or generalized joint hypermobility can result in laxity of the connective tissues supporting the patella, allowing it to sit higher.

Trauma and Injury

Acute injuries to the knee can also lead to patella alta:

• Patellar Tendon Rupture: While a complete rupture would cause the patella to migrate superiorly (patella alta), a partial tear or chronic strain can also lead to elongation of the tendon over time.
• Avulsion Fractures: A fracture where a piece of bone is pulled away by a tendon or ligament can affect the attachment point of the patellar tendon, potentially altering patellar height.
• Quadriceps Tendon Injury: Although less direct, injuries to the quadriceps tendon can indirectly affect the tension and positioning of the entire extensor mechanism.

Muscle Imbalances and Dysfunction

The balance of forces acting on the patella is crucial for its proper tracking. Imbalances can pull the patella superiorly:

• Quadriceps Dominance/Tightness: Overly strong or tight quadriceps muscles, particularly the rectus femoris, can exert excessive superior pull on the patella.
• Weakness of Stabilizing Muscles: Insufficient strength in the vastus medialis obliquus (VMO), a part of the quadriceps that helps pull the patella medially and inferiorly, can contribute to superior and lateral patellar displacement.
• Hamstring Tightness: Tight hamstrings can indirectly affect patellar position by altering pelvic tilt and overall lower limb mechanics, leading to increased strain on the quadriceps and patellar tendon.
• Gluteal Dysfunction: Weakness in the hip abductors and external rotators (e.g., gluteus medius and maximus) can lead to dynamic valgus (knee caving inward) during movement, which can alter the forces on the patella and encourage superior migration.

Connective Tissue Laxity

As mentioned under developmental factors, a generalized increase in joint flexibility due to lax connective tissues can mean the patellar tendon itself is inherently longer or more extensible, allowing the patella to sit higher.

Surgical Complications

In some rare instances, previous knee surgeries can contribute to patella alta:

• ACL Reconstruction with Patellar Tendon Graft: If the harvesting of the patellar tendon graft inadvertently leads to a lengthening of the remaining tendon, it can result in patella alta.
• Total Knee Arthroplasty (TKA): Imprecise surgical technique during TKA can sometimes alter the tension of the extensor mechanism, potentially leading to a higher patella.

Associated Symptoms and Risks

While some individuals with patella alta may be asymptomatic, many experience symptoms, particularly during physical activity:

• Anterior Knee Pain (Patellofemoral Pain Syndrome): This is the most common symptom, often described as a dull ache around or behind the kneecap, especially with activities like climbing stairs, squatting, or prolonged sitting.
• Patellar Instability: A high-riding patella is less securely seated in the trochlear groove, making it more prone to subluxation (partial dislocation) or full dislocation, especially with twisting movements.
• Clicking or Popping Sensations: Abnormal patellar tracking can lead to audible sounds during knee movement.
• Difficulty with Full Knee Extension: Paradoxically, a high patella can sometimes make it harder to achieve full extension due to altered mechanics.
• Increased Risk of Osteoarthritis: Chronic abnormal loading and tracking can lead to premature wear and tear of the articular cartilage under the patella, increasing the risk of patellofemoral osteoarthritis over time.

Diagnosis of Patella Alta

Diagnosis typically involves a combination of clinical examination and imaging:

• Clinical Examination: A healthcare professional will assess knee alignment, patellar mobility, range of motion, and muscle strength and flexibility. They may also perform specific tests to evaluate patellar tracking and stability.
• Imaging:
  • Lateral X-ray of the Knee: This is the primary diagnostic tool. Specific ratios like the Insall-Salvati ratio (patellar tendon length to patellar length) or the Blackburne-Peel ratio (distance from the inferior patellar pole to the tibial plateau to the patellar length) are measured to objectively determine patellar height. A ratio above the normal range indicates patella alta.
  • MRI: While not typically needed for initial diagnosis of patella alta itself, an MRI can provide more detailed information about soft tissues (tendons, ligaments, cartilage) and rule out other pathologies or assess damage resulting from chronic patella alta.

Management and Treatment Approaches

Treatment for patella alta is highly individualized and depends on the severity of symptoms, the underlying cause, and the presence of associated conditions like instability or pain.

Conservative Management

For most symptomatic cases, conservative treatment is the first line of approach:

• Physical Therapy: This is paramount. A physical therapist will design a program focusing on:
  • Strengthening: Emphasizing the vastus medialis obliquus (VMO) to improve patellar tracking, along with hip abductors and external rotators (glutes) to improve lower limb alignment.
  • Stretching: Addressing tightness in the quadriceps (especially rectus femoris), hamstrings, and iliotibial band (ITB).
  • Neuromuscular Re-education: Improving proprioception and control of knee movement.
  • Activity Modification: Temporarily reducing or altering activities that aggravate symptoms.
• Bracing or Taping: Patellar stabilizing braces or specific taping techniques (e.g., McConnell taping) can help improve patellar tracking and reduce pain during activity.
• Pain Management: Over-the-counter pain relievers (NSAIDs), ice, and rest can help manage acute pain episodes.
• Footwear and Orthotics: Addressing foot mechanics with appropriate footwear or custom orthotics can sometimes help improve overall lower limb alignment and reduce stress on the knee.

Surgical Intervention

Surgery is generally considered only after a comprehensive course of conservative treatment has failed, or in cases of recurrent patellar dislocation or severe instability. Surgical options aim to lower the patella or improve its tracking:

• Tibial Tubercle Osteotomy (TTO): This procedure involves cutting the bony prominence (tibial tuberosity) where the patellar tendon attaches and repositioning it distally (lower down) and sometimes medially (inward) to lower the patella and improve its alignment within the trochlear groove.
• Patellar Tendon Shortening: In very specific cases where the patellar tendon is significantly elongated, a shortening procedure might be considered, though it is less common and carries risks.
• Medial Patellofemoral Ligament (MPFL) Reconstruction: Often performed in conjunction with a TTO if significant patellar instability is present. The MPFL is a primary stabilizer against lateral patellar dislocation.

Rehabilitation and Long-Term Considerations

Regardless of the treatment approach, a structured rehabilitation program is crucial for optimal recovery and long-term success. This involves a gradual progression of exercises to restore strength, flexibility, balance, and functional movement patterns. Adherence to a maintenance exercise program is often necessary to prevent recurrence of symptoms, especially for those with underlying muscle imbalances.

When to See a Professional

If you experience persistent knee pain, instability, or suspect your kneecap might be sitting high, it is essential to consult with a healthcare professional. This could be a physician, sports medicine specialist, or orthopaedic surgeon. They can accurately diagnose the condition, rule out other potential causes of knee pain, and recommend the most appropriate and personalized treatment plan for your specific situation. Early diagnosis and intervention can significantly improve outcomes and prevent further complications.