What Causes Anterior Knee Pain Next to the Patella That Worsens with Step-Up and Step-Down Activities?
This presentation is classic for patellofemoral pain syndrome (PFPS), a multifactorial condition characterized by peripatellar or retropatellar pain that intensifies during activities that load the patellofemoral joint under flexion. 1, 2
Primary Causative Factors
The pain arises from a combination of biomechanical and neuromuscular dysfunction affecting the patellofemoral joint:
Biomechanical Contributors
- Patellar maltracking: The patella fails to glide properly in the femoral trochlear groove during knee flexion, creating abnormal stress on peripatellar structures 3
- Dynamic valgus malalignment: The knee collapses inward during weight-bearing activities, particularly during stair negotiation 3
- Abnormal foot mechanics: Excessive rearfoot eversion (pes planus/pronatus valgus) transmits abnormal forces up the kinetic chain 3
Neuromuscular Deficits
- Hip muscle weakness: Particularly hip abductor and hip extensor weakness fails to control femoral internal rotation and adduction 1, 2
- Quadriceps imbalance: Vastus medialis obliquus weakness relative to vastus lateralis creates lateral patellar tracking 3
- Hamstring and iliotibial band tightness: Restricts normal knee mechanics and increases patellofemoral joint stress 3
Tissue Overload
- Bone stress: Subchondral bone overload from repetitive loading activities is a common pain generator 4
- Synovial inflammation: Peripatellar synovial irritation from mechanical stress 4
Key Clinical Context
PFPS affects 23% of adults and 29% of adolescents, with young females disproportionately affected 2, 5. The condition is fundamentally a loss of tissue homeostasis from overload, not primarily a structural cartilage problem 4. This is critical: chondromalacia patellae is a pathological finding, not a diagnosis, and does not need to be "corrected" to relieve pain 4, 6.
Important Caveats
- Pain with prolonged sitting ("theater sign") and descending stairs are cardinal features that help distinguish PFPS from other causes 5
- Pain with squatting is the most sensitive physical examination finding 5
- The condition has a poor natural history with >50% experiencing persistent pain beyond 5 years despite treatment, emphasizing the importance of addressing underlying causes 1, 2
- PFPS may be a precursor to patellofemoral osteoarthritis, making proper management essential 1, 2
What to Look For on Examination
Examine for:
- Hip abductor strength (Trendelenburg sign during single-leg stance)
- Dynamic valgus during single-leg squat or step-down test
- Foot posture (excessive pronation)
- Hamstring and iliotibial band flexibility
- Vastus medialis obliquus bulk compared to vastus lateralis
- Patellar tracking during active knee extension
- Pain reproduction with patellar compression during knee flexion
Plain radiographs are not necessary for diagnosis but should be obtained if conservative treatment fails to exclude other pathology 5.