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Knee Pain, Anterior/patellofemoral Malalignment Syndrome

Description

  • Condition characterized by discomfort at the anterior aspect of the knee that is generally associated with activities, especially those that involve running, jumping, and climbing stairs
  • Has also been called “miserable malalignment syndrome”

Pathophysiology

  • Predisposing factors for patellofemoral malalignment syndrome include:
    • Femoral anteversion
    • Genu valgus
    • Pes planus
These 3 anatomic features have been commonly referred to as a terrible triad contributing to anterior knee pain. Because the entire kinetic chain is linked in function, malalignment at 1 area can lead to secondary stresses at a distant location.
  • Excess femoral anteversion as well as marked pes planus can contribute to the increase lateral pull on the patella and subsequent patellofemoral pain.
  • Further contributing factors include a wider pelvis and more laterally positioned tibial tubercle both of which also contribute to altered biomechanics at the knee.
  • Tight hamstrings, heel cords, and quadriceps, as well as diminished quadriceps tone, can lead to increased forces across the patellofemoral joint

Signs and Symptoms

History

  • Pain under and around the kneecap with activities including squatting, sitting for prolonged periods with the knees bent, and going up or down stairs or hills: These activities increase patellofemoral contact stress.
  • Recent history of direct trauma to the kneecap: A blunt trauma to the kneecap can cause soft tissue or subchondral contusion that may exacerbate this condition.

Physical Exam
  • Improper hip, knee, and ankle rotation as well as angulation: Improper angulation and rotation can lead to lateralized vector forces across the knee.
  • Cracking noises from the front of the knee with flexion and extension:
    • Cracking can be a sign of softening of the undersurface of the patella
    • Chondromalacia is patellar articular cartilage pathologic changes which range from mild cracking attributed to softening to locking and catching attributed to cartilage disruption.

Tests

Imaging

  • Anterior and posterior, lateral, merchant plain radiographs of the knee:
    • The merchant kneecap view shows the shape of the patella within the trochlea
    • Patients will frequently be found to have lateral patellar tilt as well as an abnormally shaped patella with excessive elongation of the lateral portion of the patella/lateral patellar facet
  • MRI: Not a 1st-line study for patellofemoral syndrome; however, it may be performed to rule out associated pathology in patients with recalcitrant pain and unusual clinical presentations.

Differential Diagnosis

  • Osgood-Schlatter disease:
    • Tenderness not at the patella but at the anterior tibial tubercle
    • A self-limiting inflammation of the apophysis that tends to occur in growing teenagers and pre-teens
    • Irregularity and fragmentation of the apophysis are seen on lateral radiographs.
  • Meniscus tear:
    • Disruption of the crescent-shaped fibrocartilaginous tissue adjacent to the tibial and femoral articular surfaces
    • Most commonly presents as posteromedial and posterolateral hemijoint tenderness with knee hyperflexion and rotation
  • Prepatellar bursitis:
    • An inflammation of the fluid-filled bursal sac beneath the SC tissue and immediately anterior to the patella
    • More common in patients who kneel for extended periods of time and has been called “carpet layer’s knee”
    • Swelling and tenderness immediately anterior to the patella; does not primarily present with deeper tenderness in the medial and lateral parapatellar regions found in patellofemoral syndrome

ALERT
Patients with a traumatic effusion, locking, catching, instability to ligamentous stress testing, multiple joint effusions, or night waking should be evaluated for other traumatic or medical conditions.

General Measures

  • A progressive exercise program is the main focus of treatment.
  • Strength and flexibility exercises are needed to increase the strength and control the quadriceps muscle as well as to stretch the quadriceps, hamstrings and tendoachilles complex.
  • Straight-leg-raising program can help to strengthen the quadriceps:
    • This can be performed several times each day as a home exercise program or formally with physical therapy in more recalcitrant cases.
    • Quadriceps, hamstrings and tendoachilles stretches can be performed at the same time intervals as the strengthening program.
  • Patients can be advanced from low-resistance exercises such as swimming, stationary bike, and elliptical trainers to higher level running activities.
  • Activity restriction in the initial acutely symptomatic stage is instituted to eliminate high-impact sports, including especially those that involve running and jumping.

ICD-9

719.46 Knee pain

FAQ

  • Q: Is it acceptable to play sports, or is this condition too dangerous?
  • A: Patients with a history of patellofemoral syndrome who have regained their strength and flexibility are permitted to return to their activities provided that they do not have pain and limping during their activities. A history of catching, locking, or knee effusions may be a sign of further biomechanical intraarticular pathology that should be addressed.
  • Q: Is bracing indicated?
  • A: Some patients with anterior knee pain respond to neoprene sleeves, and those with a component of increased lateral translation may benefit from neoprene sleeves with lateral patellar supports. Bracing, however, is not a substitute for a strength and conditioning program.
  • Q: Is chondromalacia patella the same as patellofemoral syndrome?
  • A: No. Chondromalacia is a classification of the anatomic pathologic changes of the undersurface of the patella. Patellofemoral syndrome is the clinical condition encompassing the patient’s history, physical, and radiographic elements of anterior knee pain.

AUTHOR

Theodore J. Ganley, MD

BIBLIOGRAPHY

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