Retropatellar Pain: Understanding Behind-Kneecap Issues, Causes, and Treatment

What is Retropatellar?

The term "retropatellar" literally translates to "behind the kneecap." In exercise science, kinesiology, and clinical contexts, it specifically refers to the posterior (rear) surface of the patella (kneecap) and its interaction with the femur (thigh bone) within the patellofemoral joint.

Understanding the Patellofemoral Joint

To fully grasp what "retropatellar" signifies, it's essential to understand the anatomy and function of the patellofemoral joint, a crucial component of the human knee.

• Anatomy of the Patella: The patella, or kneecap, is a sesamoid bone, meaning it is embedded within a tendon—specifically, the quadriceps tendon. Its primary role is to increase the mechanical advantage of the quadriceps muscle, allowing for more efficient extension of the knee.
• The Retropatellar Surface: The posterior aspect of the patella, known as the retropatellar surface, is covered with a thick layer of articular cartilage. This smooth, slippery tissue reduces friction and facilitates gliding as the patella moves within the trochlear groove (a V-shaped groove at the end of the femur) during knee flexion and extension.
• Role of Articular Cartilage: Articular cartilage is vital for joint health, providing a low-friction surface that allows bones to glide effortlessly against each other. It also acts as a shock absorber, distributing forces across the joint.

What Does "Retropatellar" Refer To?

In a general sense, "retropatellar" defines the anatomical space and structures located directly behind the patella. However, it is most commonly used in a clinical context to describe conditions or symptoms originating from this specific area. When someone refers to "retropatellar pain," they are indicating discomfort or pathology arising from the patellofemoral joint, particularly involving the articular cartilage or the underlying bone of the patella or femoral trochlea.

Common Conditions Associated with the Retropatellar Region

Several conditions can cause pain or dysfunction in the retropatellar area. These are often grouped under the umbrella of "anterior knee pain."

• Patellofemoral Pain Syndrome (PFPS): This is the most common cause of retropatellar pain, characterized by pain around or behind the kneecap that worsens with activities like squatting, climbing stairs, running, or prolonged sitting with bent knees ("movie theater sign"). It's often multifactorial, involving biomechanical imbalances, overuse, and muscular weakness.
• Chondromalacia Patellae: This term specifically refers to the softening, fraying, or breakdown of the articular cartilage on the retropatellar surface. While often used interchangeably with PFPS, chondromalacia is a pathological change in the cartilage itself, whereas PFPS is a broader diagnosis for pain in the region without necessarily implying cartilage damage. Chondromalacia can be a cause of PFPS.
• Patellar Tendinopathy (Jumper's Knee): While primarily affecting the patellar tendon (below the kneecap), pain can sometimes radiate or be perceived as originating from the retropatellar area, especially during activities that heavily load the quadriceps and patellar tendon.
• Osteoarthritis: In older individuals, degenerative changes (osteoarthritis) can affect the patellofemoral joint, leading to cartilage loss, bone spur formation, and chronic retropatellar pain.

Symptoms of Retropatellar Issues

Symptoms originating from the retropatellar region typically include:

• Pain Characteristics:
  • Dull, aching pain located behind or around the kneecap.
  • Worsens with activities that load the patellofemoral joint (e.g., squatting, lunging, running, jumping, climbing/descending stairs).
  • Pain after prolonged sitting with bent knees.
  • Pain during or after exercise.
• Other Symptoms:
  • Grinding, popping, or clicking sensations (crepitus) with knee movement.
  • Occasional buckling or giving way of the knee.
  • Mild swelling around the kneecap, though often absent.

Common Causes and Risk Factors

Retropatellar pain is rarely due to a single cause but rather a combination of factors:

• Biomechanical Factors:
  • Poor Patellar Tracking: The patella may not glide smoothly in the trochlear groove, leading to increased friction or pressure on specific areas of the retropatellar cartilage.
  • Foot Pronation: Excessive inward rolling of the foot can alter the alignment of the lower kinetic chain, influencing knee mechanics.
  • Excessive Q-angle: A larger angle between the quadriceps femoris muscle and the patellar tendon can increase lateral pull on the patella.
• Overuse and Training Errors:
  • Sudden increases in training volume, intensity, or frequency.
  • Inadequate rest and recovery between training sessions.
  • Repetitive activities involving knee bending (e.g., cycling, running, jumping sports).
• Muscle Imbalances:
  • Weak Quadriceps: Especially the vastus medialis obliquus (VMO), which helps stabilize the patella.
  • Tight Hamstrings, Quadriceps, or Calf Muscles: Can alter forces across the knee joint.
  • Weak Gluteal Muscles (particularly gluteus medius): Can lead to hip adduction and internal rotation, putting increased stress on the knee.
• Anatomical Variations:
  • Shallow trochlear groove.
  • Patella alta (high-riding patella) or patella baja (low-riding patella).
• Trauma: Direct impact to the kneecap, though less common as a primary cause of chronic retropatellar pain.

Diagnosis of Retropatellar Conditions

Diagnosis typically involves a thorough clinical assessment:

• Clinical Examination: A healthcare professional (physician, physical therapist, kinesiologist) will assess knee range of motion, observe patellar tracking, palpate for tenderness, and perform specific tests to evaluate muscle strength, flexibility, and alignment of the lower extremity.
• Imaging Studies:
  • X-rays: Can rule out fractures, arthritis, or bony abnormalities.
  • MRI (Magnetic Resonance Imaging): Provides detailed images of soft tissues, including articular cartilage, tendons, and ligaments. It can identify cartilage damage (chondromalacia) but is not always necessary for diagnosing PFPS.

Management and Treatment Approaches

Treatment for retropatellar issues is predominantly conservative and aims to reduce pain, improve function, and address underlying biomechanical factors.

• Conservative Management:
  • Rest and Activity Modification: Reducing or temporarily stopping activities that aggravate pain.
  • Ice: Applying ice to the affected area to reduce inflammation and pain.
  • NSAIDs (Non-Steroidal Anti-Inflammatory Drugs): Over-the-counter medications like ibuprofen can help manage pain and inflammation.
  • Physical Therapy/Rehabilitation: This is the cornerstone of treatment.
    • Strengthening Exercises: Focusing on the quadriceps (especially VMO), gluteal muscles (hip abductors and external rotators), and core muscles.
    • Stretching Exercises: Addressing tightness in hamstrings, quadriceps, hip flexors, and calf muscles.
    • Proprioception and Balance Training: Improving knee stability and control.
    • Patellar Taping or Bracing: May provide temporary pain relief and improve patellar tracking.
• Biomechanical Correction:
  • Footwear Assessment: Ensuring appropriate and supportive footwear for activities.
  • Orthotics: Custom or over-the-counter shoe inserts to correct excessive foot pronation.
• Injections: Rarely used for PFPS, but corticosteroids or hyaluronic acid injections might be considered in specific cases of severe osteoarthritis or inflammation.
• Surgical Intervention: Considered only in very rare cases where conservative treatment has failed for an extended period, and a specific anatomical issue (e.g., severe maltracking, significant cartilage defect) is identified. Procedures might include lateral retinacular release or realignment surgeries.

Prevention Strategies

Preventing retropatellar issues often involves smart training practices and addressing potential risk factors:

• Gradual Progression: Slowly increasing the intensity, duration, or frequency of exercise.
• Proper Form: Maintaining correct technique during exercises and activities, especially squats, lunges, and running.
• Strength and Flexibility: Regularly performing exercises that strengthen the quadriceps, glutes, and core, and stretch tight muscle groups.
• Appropriate Footwear: Wearing supportive shoes that are suitable for your activity and foot type, replacing them when worn out.

When to Seek Professional Help

If you experience persistent pain behind your kneecap that doesn't improve with rest and basic self-care, or if the pain significantly interferes with your daily activities or exercise, it is advisable to consult a healthcare professional. An accurate diagnosis is crucial for effective management and to rule out more serious conditions.