Medial Knee Pain: Causes, Symptoms, and Management During Leg Extension

Why does the inside of my knee hurt when I extend my leg?

Pain on the inside (medial aspect) of the knee during leg extension often indicates an issue with structures such as the medial collateral ligament (MCL), medial meniscus, pes anserine bursa/tendons, or medial compartment cartilage. The specific cause depends on the pain's nature, onset, and accompanying symptoms.

Understanding Knee Anatomy & Extension

To understand why medial knee pain occurs during extension, it's crucial to grasp the key anatomical structures involved and their roles:

• Medial Collateral Ligament (MCL): A strong ligament on the inner side of the knee that prevents the knee from bending inward (valgus stress). It is taut during knee extension, providing stability.
• Medial Meniscus: A C-shaped piece of cartilage that acts as a shock absorber and helps distribute weight evenly across the joint. It can be compressed or pinched during knee movements.
• Pes Anserine Bursa/Tendons: The pes anserine bursa is a fluid-filled sac located on the inner side of the knee, beneath the insertion of three tendons: the sartorius, gracilis, and semitendinosus. These muscles contribute to knee flexion and internal rotation.
• Articular Cartilage: The smooth, slippery tissue covering the ends of the bones (femur and tibia) within the joint, allowing for frictionless movement. The medial compartment refers to the inner side of this joint space.
• Medial Plica: A fold in the synovial membrane (lining of the joint) that can sometimes become irritated or inflamed.
• Adductor Muscles: Located on the inner thigh, these muscles (e.g., adductor magnus, longus, brevis) can have tendons that attach near the medial knee, and their overuse or strain can refer pain.

Leg extension involves the contraction of the quadriceps muscles (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius) to straighten the knee joint. This movement places stress and movement on all surrounding structures, making them susceptible to irritation or injury if compromised.

Common Causes of Medial Knee Pain During Extension

Several conditions can lead to pain on the inside of the knee during leg extension:

• Medial Collateral Ligament (MCL) Sprain/Injury:
  • Mechanism: Often results from a direct blow to the outside of the knee, forcing it inward (valgus stress), or from sudden twisting movements.
  • Pain Profile: Pain is typically felt directly on the inside of the knee. It worsens with valgus stress (pushing the knee inward) and can be noticeable during extension as the MCL becomes taut.
  • Accompanying Symptoms: Tenderness to touch along the MCL, swelling, and sometimes instability (feeling like the knee might give way).
• Medial Meniscus Tear:
  • Mechanism: Can occur due to sudden twisting with the foot planted, deep squatting, or degeneration over time.
  • Pain Profile: Pain is often sharp or aching, located along the medial joint line. It may be worse with full extension, twisting, or squatting. A "clicking," "popping," or "locking" sensation can be present if a piece of the meniscus gets caught.
  • Accompanying Symptoms: Swelling, tenderness along the joint line, and mechanical symptoms like catching or locking.
• Pes Anserine Bursitis or Tendinopathy:
  • Mechanism: Inflammation of the pes anserine bursa or irritation/degeneration of the sartorius, gracilis, or semitendinosus tendons. Often caused by overuse, tight hamstrings, improper running mechanics, or increased activity.
  • Pain Profile: Pain is typically felt about 2-3 inches below the joint line on the inner side of the knee. It's often worse with activities that involve knee flexion/extension, climbing stairs, or getting up from a chair.
  • Accompanying Symptoms: Localized tenderness to touch, swelling (less common for tendinopathy), and pain that may worsen with repetitive knee bending and straightening.
• Medial Compartment Osteoarthritis (OA):
  • Mechanism: Degeneration of the articular cartilage on the inner side of the knee joint. More common with age, previous injury, or obesity.
  • Pain Profile: Aching pain that often worsens with activity, particularly weight-bearing movements like standing, walking, or extending the leg under load. Morning stiffness is common.
  • Accompanying Symptoms: Stiffness, swelling, grinding sensations (crepitus), and reduced range of motion.
• Medial Plica Syndrome:
  • Mechanism: The medial plica, a normal fold of synovial tissue, can become irritated, thickened, or inflamed due to overuse, trauma, or repetitive knee movements.
  • Pain Profile: Often presents as a dull ache on the inside of the kneecap or just above the medial joint line, sometimes with a "snapping" or "popping" sensation during knee flexion and extension. Pain can worsen with activity.
  • Accompanying Symptoms: Tenderness, sometimes a palpable cord-like structure, and occasionally pseudo-locking.
• Adductor Tendinopathy/Strain:
  • Mechanism: Inflammation or strain of the tendons of the adductor muscles (inner thigh muscles) where they attach near the knee. Common in athletes involved in kicking or quick directional changes.
  • Pain Profile: Pain can be felt high on the inner thigh and refer down towards the medial knee, especially during movements that load the adductors, including leg extension if these muscles are strained.
  • Accompanying Symptoms: Tenderness along the inner thigh/groin, pain with resisted adduction.

Identifying the Specific Cause

While self-assessment can provide clues, a definitive diagnosis requires professional evaluation. Consider these questions:

• Onset: Was there a specific injury (trauma, twist) or did the pain develop gradually?
• Nature of Pain: Is it sharp, aching, burning, or dull?
• Accompanying Symptoms: Is there swelling, warmth, redness, clicking, popping, locking, or instability?
• Aggravating Factors: What activities make it worse (e.g., walking, stairs, squatting, specific exercises)?
• Relieving Factors: What makes it better (e.g., rest, ice)?
• Location: Can you pinpoint the exact spot of pain?

Initial Self-Care and Management Strategies

For acute or mild pain, these strategies may help:

• RICE Protocol:
  • Rest: Avoid activities that aggravate the pain.
  • Ice: Apply ice packs to the affected area for 15-20 minutes, several times a day, especially after activity.
  • Compression: Use a compression bandage to help reduce swelling.
  • Elevation: Elevate the leg above heart level when resting to reduce swelling.
• Activity Modification: Temporarily reduce or modify exercises that provoke pain. For example, reduce the range of motion during leg extensions or switch to non-weight-bearing exercises.
• Over-the-Counter Pain Relief: Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen can help manage pain and inflammation, but should be used cautiously and as directed.
• Gentle Mobility: If pain allows, very gentle, pain-free range of motion exercises can prevent stiffness. Avoid forceful extension.

Prevention Strategies

Proactive measures can help minimize the risk of medial knee pain:

• Proper Warm-up and Cool-down: Prepare muscles and joints for activity and aid recovery.
• Balanced Strength and Flexibility:
  • Strengthen: Quadriceps, hamstrings, glutes, and hip abductors/adductors to ensure overall knee stability.
  • Flexibility: Maintain good flexibility in hamstrings, quadriceps, and hip adductors.
• Gradual Progression: Increase the intensity, duration, or resistance of exercises slowly to allow your body to adapt.
• Correct Biomechanics and Form: Pay attention to proper technique during exercises and daily activities. Avoid "knees caving in" during squats or lunges.
• Appropriate Footwear: Wear supportive shoes that are suitable for your activity and replace them when worn out.
• Listen to Your Body: Do not push through pain. Pain is a signal that something is wrong.

When to Seek Professional Medical Attention

Consult a healthcare professional (e.g., physician, sports medicine specialist, physical therapist) if you experience:

• Severe pain that prevents you from bearing weight.
• Sudden onset of swelling or bruising.
• Feeling of instability or the knee "giving way."
• Locking or catching sensations in the knee.
• Inability to fully extend or bend your knee.
• Pain that worsens or does not improve with rest and self-care within a few days.
• Pain accompanied by fever or redness, which could indicate infection.

Ignoring persistent knee pain can lead to chronic issues or further injury. A professional evaluation can accurately diagnose the cause and establish an appropriate treatment plan, which may include physical therapy, injections, or, in some cases, surgical intervention.

Conclusion

Pain on the inside of the knee during leg extension is a common complaint with several potential culprits, ranging from ligament sprains and meniscal tears to tendinopathies and degenerative changes. Understanding the underlying anatomy and the specific nature of your symptoms is the first step toward effective management. While initial self-care can be beneficial, persistent or severe pain warrants a professional medical evaluation to ensure an accurate diagnosis and a tailored recovery plan. Prioritizing proper training techniques, balanced strength, and listening to your body's signals are paramount in maintaining long-term knee health.