Pain Behind the Kneecap: Causes, Symptoms, Diagnosis, and Treatment

What is the pain behind the kneecap?

Pain behind the kneecap, medically known as retropatellar pain, is a common complaint often indicative of an issue with the patellofemoral joint or surrounding structures. It typically arises from overuse, biomechanical imbalances, or direct trauma, leading to irritation or degeneration of the cartilage, tendons, or other soft tissues.

Understanding the Knee Joint and Patella

To understand pain behind the kneecap, it's essential to first grasp the basic anatomy and function of the knee joint, particularly the patellofemoral joint. The knee is a complex hinge joint primarily formed by the articulation of three bones: the femur (thigh bone), tibia (shin bone), and patella (kneecap).

The patella is a sesamoid bone, meaning it's embedded within a tendon – specifically, the quadriceps tendon above and the patellar tendon below. It sits in a groove at the end of the femur called the trochlear groove. Its primary role is to increase the mechanical advantage of the quadriceps muscles, allowing them to exert more force on the tibia during leg extension. It also protects the knee joint.

Crucially, the undersurface of the patella and the trochlear groove are covered by articular cartilage, a smooth, slippery tissue that allows the bones to glide effortlessly during movement. Pain behind the kneecap often originates when this gliding mechanism is disrupted, or the surrounding soft tissues become irritated or damaged.

Common Causes of Pain Behind the Kneecap

Pain behind the kneecap can stem from various conditions, many of which are interconnected and share similar symptoms.

• Patellofemoral Pain Syndrome (PFPS)
  • Description: This is the most common cause of pain behind the kneecap, often referred to as "runner's knee" or "anterior knee pain." It's characterized by a dull, aching pain around or behind the patella. PFPS is not a specific injury but rather a syndrome resulting from multifactorial issues that cause the patella to not track smoothly within the femoral groove.
  • Mechanism: Imbalances in muscle strength (e.g., weak vastus medialis obliquus, tight IT band, weak glutes), poor foot mechanics, overuse, or sudden increases in activity can lead to abnormal forces on the patellofemoral joint.
  • Symptoms: Pain worsens with activities that load the patellofemoral joint, such as squatting, kneeling, going up or down stairs, prolonged sitting (known as "theater sign"), and running.
• Chondromalacia Patellae
  • Description: This refers to the softening and breakdown of the articular cartilage on the underside of the patella. While often associated with PFPS, chondromalacia is a pathological finding (cartilage damage) whereas PFPS describes the symptoms.
  • Mechanism: Repetitive stress, trauma, or abnormal patellar tracking can lead to the erosion of this protective cartilage.
  • Symptoms: Similar to PFPS, including pain with activity, grinding or cracking sensations (crepitus) during knee movement.
• Patellar Tendinopathy (Jumper's Knee)
  • Description: This condition involves pain and degeneration of the patellar tendon, which connects the patella to the tibia. While the pain is typically just below the kneecap, it can radiate and be perceived as "behind" the kneecap, especially during activities involving forceful knee extension.
  • Mechanism: Primarily an overuse injury, common in athletes involved in jumping and explosive movements.
  • Symptoms: Localized pain and tenderness at the bottom of the kneecap, worsening with jumping, squatting, and running.
• Quadriceps Tendinopathy
  • Description: Similar to patellar tendinopathy, but affecting the quadriceps tendon above the kneecap.
  • Mechanism: Overuse, often seen in weightlifters or athletes involved in repetitive kicking or jumping.
  • Symptoms: Pain and tenderness at the top of the kneecap, which can feel like it's "behind" the patella during certain movements.
• Bursitis
  • Description: Inflammation of a bursa, a small fluid-filled sac that reduces friction between tissues. Several bursae are around the knee. While prepatellar bursitis (in front of the kneecap) is common, infrapatellar bursitis (below the kneecap) or even an inflamed deep suprapatellar bursa can cause pain that feels posterior to the patella.
  • Mechanism: Repetitive kneeling, direct trauma, or infection.
  • Symptoms: Localized swelling, tenderness, warmth, and pain that worsens with movement or pressure.
• Osteoarthritis (Patellofemoral OA)
  • Description: Degenerative "wear and tear" arthritis affecting the patellofemoral joint. It's more common in older adults but can occur younger due to previous injury or overuse.
  • Mechanism: Gradual breakdown of articular cartilage over time.
  • Symptoms: Persistent pain, stiffness, grinding sensations, especially in the morning or after rest, and pain with activities like stairs.
• Plica Syndrome
  • Description: The plica are normal folds in the synovial membrane (lining) of the knee joint. Sometimes, one of these folds, often the medial plica, can become thickened, inflamed, and irritated, getting pinched between the patella and femur.
  • Mechanism: Repetitive knee bending, direct trauma, or overuse.
  • Symptoms: Aching pain, clicking, snapping, or popping sensation, sometimes a feeling of the knee "giving way."
• Fat Pad Impingement (Hoffa's Syndrome)
  • Description: Inflammation or impingement of the infrapatellar fat pad (Hoffa's fat pad), a fatty cushion located behind and below the patella.
  • Mechanism: Hyperextension injuries, direct trauma, or repetitive compression.
  • Symptoms: Pain and tenderness below the kneecap, often worse with full knee extension or activities that compress the fat pad.
• Referred Pain
  • Less commonly, pain behind the kneecap can be referred from other areas, such as the hip or lumbar spine, though this is usually accompanied by other symptoms in those regions.

Symptoms to Look For

While the underlying cause can vary, pain behind the kneecap often presents with common characteristics:

• Dull, aching pain: Often diffuse, making it hard to pinpoint the exact location.
• Pain with specific activities:
  • Going up or down stairs.
  • Squatting, lunging, or kneeling.
  • Running, especially downhill.
  • Prolonged sitting with bent knees ("theater sign").
  • Standing up after sitting for a long time.
• Grinding, clicking, or popping sensations (crepitus): May or may not be painful.
• Tenderness: When pressing on the edges of the kneecap.
• Mild swelling: Around the kneecap.
• Feeling of instability or "giving way": Though less common, can occur.

Diagnosis and Professional Assessment

Accurate diagnosis is crucial for effective treatment. If you experience persistent pain behind the kneecap, especially if it interferes with daily activities or training, consulting a healthcare professional is recommended. This could be your general practitioner, a sports medicine physician, an orthopedic surgeon, or a physical therapist.

A thorough assessment will typically include:

• Medical History: Questions about your symptoms, activity levels, previous injuries, and general health.
• Physical Examination: Evaluation of your knee's range of motion, strength, stability, patellar tracking, and palpation to identify tender spots. The examiner may assess your hip and ankle mechanics as well, due to their influence on knee function.
• Imaging Studies:
  • X-rays: Useful for assessing bone alignment, ruling out fractures, and detecting signs of arthritis.
  • MRI (Magnetic Resonance Imaging): Provides detailed images of soft tissues like cartilage, tendons, ligaments, and bursae, helpful for diagnosing conditions like chondromalacia, tendinopathy, or plica syndrome.
  • Ultrasound: Can be used to visualize tendons, bursae, and soft tissue inflammation in real-time.

Management and Treatment Approaches

Treatment for pain behind the kneecap is highly individualized and depends on the underlying cause and severity. Most cases respond well to conservative management.

• Conservative Management (First-Line):
  • Rest and Activity Modification: Reducing or temporarily stopping activities that aggravate the pain is crucial. This doesn't necessarily mean complete rest but rather modifying intensity, duration, or type of exercise.
  • Ice Application: Applying ice packs to the affected area for 15-20 minutes several times a day can help reduce pain and inflammation, especially after activity.
  • Over-the-Counter Pain Relievers: Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen can help manage pain and inflammation.
  • Physical Therapy: This is often the cornerstone of treatment and focuses on addressing biomechanical imbalances. A physical therapist will design a program that may include:
    • Strengthening Exercises: Targeting the quadriceps (especially the vastus medialis obliquus), gluteal muscles (gluteus medius and maximus), and core muscles to improve stability and alignment.
    • Flexibility and Stretching: Addressing tightness in the quadriceps, hamstrings, calf muscles, and IT band.
    • Patellar Taping or Bracing: Kinesiology tape or specific knee braces can help improve patellar tracking and reduce pain during activity.
    • Biomechanical Correction: Analyzing gait, running form, and squat mechanics to identify and correct faulty movement patterns.
    • Eccentric Training: Specific exercises (e.g., eccentric squats) are particularly effective for tendinopathies.
• Other Interventions:
  • Orthotics: Custom or over-the-counter shoe inserts can help correct foot mechanics (e.g., overpronation) that contribute to patellofemoral pain.
  • Injections: In some cases, a doctor might consider corticosteroid injections to reduce inflammation, though these are used cautiously due to potential side effects and are generally not a long-term solution. Platelet-rich plasma (PRP) or hyaluronic acid injections are being explored for certain conditions but are not standard for most PFPS.
• Surgical Intervention:
  • Surgery is rarely needed for pain behind the kneecap and is typically considered only after extensive conservative treatment has failed for specific diagnosed conditions (e.g., severe chondromalacia, persistent plica syndrome, or significant patellar maltracking). Procedures might include arthroscopy to debride damaged cartilage, lateral retinacular release to improve patellar tracking, or tibial tubercle osteotomy to realign the patella.

Prevention Strategies

Preventing pain behind the kneecap often involves addressing the same factors that cause it:

• Gradual Progression: Increase the intensity, duration, or frequency of your workouts gradually. Avoid sudden spikes in training load.
• Proper Warm-up and Cool-down: Prepare your muscles for activity and aid recovery.
• Strength and Flexibility Balance: Maintain balanced strength in your quadriceps, hamstrings, glutes, and core. Ensure adequate flexibility in all major leg muscle groups.
• Appropriate Footwear: Wear supportive shoes suitable for your activity, and replace them regularly. Consider orthotics if you have foot pronation issues.
• Proper Technique: Learn and practice correct form for exercises like squats, lunges, and running to minimize stress on the knee joint.
• Listen to Your Body: Do not push through pain. If you feel discomfort, reduce the intensity or take a break.

When to See a Doctor

While many cases of pain behind the kneecap can be managed with self-care and activity modification, seek professional medical attention if:

• Your pain is severe or debilitating.
• You experience sudden onset of pain after an injury.
• There is significant swelling, redness, or warmth around the knee.
• You cannot bear weight on your leg.
• Your knee locks, clicks loudly, or gives way.
• Your pain does not improve after several weeks of conservative management.

By understanding the potential causes and adopting a proactive approach to management and prevention, you can effectively address and often overcome pain behind the kneecap, allowing you to continue pursuing your fitness goals.