Wear Behind the Kneecap: Causes, Symptoms, and Treatment

What is the wear behind the kneecap?

The "wear behind the kneecap" typically refers to the degeneration or softening of the articular cartilage on the underside of the patella (kneecap), a condition often termed chondromalacia patellae or patellofemoral pain syndrome, and in more advanced stages, patellofemoral osteoarthritis.

Understanding the Patellofemoral Joint

To comprehend what "wear" behind the kneecap entails, it's crucial to first understand the anatomy and function of the patellofemoral joint. This joint is formed by the patella (kneecap) and the trochlear groove at the end of the femur (thigh bone), where the patella slides up and down during knee flexion and extension.

• The Patella: A sesamoid bone embedded within the quadriceps tendon, the patella acts as a pulley, increasing the mechanical advantage of the quadriceps muscles. This significantly improves the efficiency of knee extension.
• Articular Cartilage: Both the underside of the patella and the trochlear groove of the femur are covered with a smooth, slippery tissue called articular cartilage. This specialized cartilage provides a low-friction surface, allowing the patella to glide effortlessly within the groove, absorbing shock and distributing forces across the joint during movement.

What "Wear" Behind the Kneecap Means

When people refer to "wear behind the kneecap," they are describing a process of degradation affecting this crucial articular cartilage. This can manifest in several ways:

• Chondromalacia Patellae: This is the initial softening and fraying of the articular cartilage on the back of the patella. It's often seen in younger, active individuals and can progress in severity.
• Patellofemoral Pain Syndrome (PFPS): While PFPS is a broader term encompassing pain around the kneecap, chondromalacia is often a contributing factor. PFPS is characterized by anterior knee pain that worsens with activities that load the patellofemoral joint, such as squatting, stair climbing, or prolonged sitting.
• Patellofemoral Osteoarthritis: This represents a more advanced stage of cartilage degeneration, where the "wear" has progressed to significant loss of cartilage, leading to bone-on-bone friction and inflammatory changes within the joint. This is more common with age but can occur earlier due to injury or chronic mechanical stress.

The "wear" process compromises the smooth gliding mechanism, leading to increased friction, inflammation, and pain.

Causes and Contributing Factors

The degeneration of cartilage behind the kneecap is rarely due to a single cause but rather a combination of biomechanical, overuse, and anatomical factors:

• Biomechanical Imbalances:
  • Quadriceps Muscle Imbalance: Weakness or imbalance between the vastus medialis obliquus (VMO) and the vastus lateralis can cause the patella to track improperly, pulling it laterally out of the trochlear groove.
  • Tightness of Soft Tissues: Tight hamstrings, quadriceps, gastrocnemius (calf muscles), or particularly the iliotibial (IT) band can alter the mechanics of the knee and patellar tracking.
  • Foot Mechanics: Excessive pronation (flat feet) can internally rotate the tibia and femur, increasing the valgus (knock-knee) stress on the knee and affecting patellar alignment.
  • Gluteal Weakness: Weakness in the hip abductors and external rotators (e.g., gluteus medius) can lead to hip adduction and internal rotation during movement, placing increased stress on the patellofemoral joint.
  • Core Instability: A weak core can contribute to poor lower extremity mechanics and increased load on the knees.
• Overuse and Training Errors:
  • Sudden Increase in Activity: Rapidly increasing the intensity, duration, or frequency of activities that load the knee (e.g., running, jumping, cycling, squatting) without proper conditioning.
  • Repetitive Impact Activities: High-impact sports or activities involving repetitive knee bending can progressively stress the cartilage.
  • Improper Technique: Poor form during exercises (e.g., squats, lunges) can place undue stress on the patellofemoral joint.
• Trauma:
  • Direct Impact: A fall or direct blow to the kneecap can damage the articular cartilage.
  • Patellar Dislocation/Subluxation: Episodes where the kneecap temporarily or completely slips out of its groove can cause acute cartilage damage.
• Anatomical Factors:
  • Patellar Malalignment: Conditions like patella alta (high-riding patella) or patella baja (low-riding patella) can predispose to improper tracking.
  • Trochlear Dysplasia: An abnormally shallow or flat trochlear groove can make the patella unstable and prone to poor tracking.
  • Increased Q-Angle: A larger angle formed by the quadriceps tendon and patellar tendon can increase the lateral pull on the patella.
• Age: As we age, the cumulative stress on joints can lead to natural wear and tear, increasing the risk of osteoarthritis.

Common Symptoms

The symptoms of "wear behind the kneecap" typically include:

• Anterior Knee Pain: Pain located around or behind the kneecap, often described as dull and aching, but can be sharp with certain movements.
• Pain with Specific Activities: Aggravated by activities that load the patellofemoral joint, such as:
  • Going up or down stairs
  • Squatting, kneeling, or lunging
  • Prolonged sitting with bent knees ("movie-goer's sign")
  • Running, especially downhill
• Crepitus: Grinding, clicking, popping, or crunching sensations felt or heard during knee movement. This can be painless, but if accompanied by pain, it often indicates cartilage irregularities.
• Swelling: While less common in early stages, inflammation can lead to mild swelling around the kneecap.
• Stiffness: A feeling of stiffness, particularly after periods of inactivity.

Diagnosis

Diagnosis typically involves a thorough clinical evaluation by a healthcare professional, such as an orthopedic surgeon, sports medicine physician, or physical therapist:

• Medical History and Physical Examination: The clinician will inquire about symptoms, activity levels, and past injuries. A physical exam will assess knee alignment, range of motion, patellar tracking, muscle strength, flexibility, and palpate for tenderness. Special tests may be performed to reproduce pain or assess patellar stability.
• Imaging Studies:
  • X-rays: Can show the alignment of the patella, the shape of the trochlear groove, and rule out other bone pathologies. They are less effective at visualizing early cartilage damage directly but can show joint space narrowing in advanced osteoarthritis.
  • Magnetic Resonance Imaging (MRI): Provides detailed images of soft tissues, including articular cartilage, ligaments, and tendons. An MRI can directly visualize cartilage defects, swelling within the bone, and other subtle soft tissue abnormalities.

Management and Treatment Strategies

The primary goal of treatment for "wear behind the kneecap" is to reduce pain, improve function, and slow down or prevent further cartilage degeneration. Conservative management is almost always the first line of approach.

• Conservative Management:
  • Rest and Activity Modification: Temporarily reducing or avoiding activities that aggravate the pain is crucial to allow the joint to recover. Low-impact alternatives (e.g., swimming, cycling with low resistance) can be substituted.
  • Ice and Anti-inflammatory Medication: Applying ice packs to the affected area can help reduce pain and inflammation. Over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen may also be recommended.
  • Physical Therapy: This is the cornerstone of conservative treatment. A tailored program will focus on:
    • Strengthening: Targeting the quadriceps (especially the VMO), gluteal muscles (gluteus medius and maximus), and core muscles to improve lower extremity mechanics and support the knee.
    • Flexibility: Stretching tight muscles such as the hamstrings, quadriceps, IT band, and calf muscles to restore normal range of motion and reduce adverse pulling forces on the patella.
    • Proprioception and Balance Training: Exercises to improve neuromuscular control and stability around the knee joint.
    • Gait Analysis and Correction: Identifying and correcting abnormal walking or running patterns.
    • Patellar Taping or Bracing: Kinesiology tape or specialized patellofemoral braces can help improve patellar tracking and reduce pain during activity.
  • Footwear and Orthotics: Addressing biomechanical issues at the foot level with appropriate supportive footwear or custom orthotics can help improve knee alignment.
• Injections:
  • Corticosteroid Injections: Can provide temporary relief from pain and inflammation, but are not a long-term solution and typically not recommended for isolated cartilage wear.
  • Hyaluronic Acid Injections: "Lubricant" injections that may provide some pain relief and improve joint function, particularly in cases of osteoarthritis.
  • Platelet-Rich Plasma (PRP) Injections: Derived from the patient's own blood, PRP contains growth factors that may promote healing, though evidence for cartilage regeneration is still evolving.
• Surgical Intervention: Surgery is typically considered only after conservative measures have failed and for specific structural issues or advanced disease. Procedures may include:
  • Arthroscopy: A minimally invasive procedure to debride (clean up) frayed cartilage, remove loose bodies, or perform a lateral retinacular release (cutting a tight ligament on the outside of the patella to improve tracking).
  • Tibial Tubercle Osteotomy: Involves moving the attachment point of the patellar tendon on the tibia to improve patellar tracking.
  • Cartilage Repair/Restoration Procedures: For severe, localized cartilage defects, techniques like microfracture, autologous chondrocyte implantation (ACI), or osteochondral allograft transplantation (OATs) may be considered, but these are complex and for specific cases.

Prevention

Preventing "wear behind the kneecap" largely involves addressing modifiable risk factors and maintaining optimal knee health:

• Gradual Progression of Training: Avoid sudden increases in the intensity, duration, or frequency of your workouts. Follow the "10% rule" – increase your training load by no more than 10% per week.
• Proper Warm-up and Cool-down: Always include dynamic warm-ups before exercise and static stretches during your cool-down.
• Balanced Strength and Flexibility Program: Focus on strengthening the quadriceps, glutes, and core, and ensure adequate flexibility in the hamstrings, quads, IT band, and calves.
• Appropriate Footwear: Wear supportive shoes that are appropriate for your activity and replace them regularly. Consider orthotics if you have significant foot biomechanical issues.
• Listen to Your Body: Pay attention to pain signals. Persistent pain is a sign to rest, modify activity, and seek professional advice.
• Maintain a Healthy Weight: Excess body weight places additional stress on the knee joints.

Understanding "wear behind the kneecap" is key to effective management. By addressing underlying causes, adhering to a structured rehabilitation program, and adopting preventive measures, individuals can significantly reduce pain, improve function, and maintain an active lifestyle.