Knee

Patellofemoral Syndrome

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Patellofemoral Syndrome, Chondromalacia Patellae, Patellofemoral Pain Syndrome, Miserable Malalignment Syndrome, Runner's Knee, PFPS

  • Epidemiology
  1. Most common Running Injury
  2. Incidence: 6% in U.S.
  3. Females account for 55% of cases
  • Risk Factors
  1. Female gender
  2. Overuse
  3. Provocative activities
    1. Running
    2. Squatting
    3. Climbing stairs (and going downstairs)
  4. Mechanical factors
    1. Dynamic valgus (with maltracking) - see below
    2. Rear foot eversion
    3. Pes pronatus
    4. Patellar instability
    5. Quadriceps weakness
  1. Soft tissue causes
    1. Prepatellar Bursitis
    2. Patella Tendonitis
    3. Meniscus Tear
  2. Articular causes
    1. Chondromalacia Patellae
    2. Patella Osteoarthritis
    3. Osteochondritis Dissecans of the Knee
    4. Chondral Fracture
  3. Functional causes
    1. Patella instability
    2. Synovial plica
      1. Synovium caught between Patella and femur
  4. Referred pain
    1. Back pain
    2. Hip Pain
    3. Ankle pain
  • Mechanism
  1. Overuse syndrome in athletes
    1. Sports involving Running, jumping or cutting
    2. Cyclist or runner going too far, too soon, too fast
    3. Basketball and Volleyball with repetitive jumping
    4. Frequent change of playing surface (grass to wood)
    5. Repetitive squats or lunges
    6. Excessively worn shoes
    7. Contact Sports (Football or Rugby)
      1. Direct impact to Patella
  2. Degeneration of Patella
    1. Chondromalacia Patellae
    2. Osteoarthritis of the knee
  3. Patella mal-tracking in the patellofemoral groove
    1. Asymmetric quadriceps Muscle Strength
    2. Vastus medialis is often weaker than other Muscle
    3. Patella is often pulled to the outside (J-tracking)
    4. Results in local wearing of the articular cartilage
    5. Increased risk in load bearing positions such as squatting
  4. Anatomic variation: Increased Q-Angle
    1. Increased angle between femur and tibia (Q-Angle)
      1. Women more often have larger Q-angle
      2. However Q-angle has not been consistently shown as significant risk
    2. On Quadriceps contraction, Patella is pushed outward
    3. Leads to mal-tracking of the Patella as above
  5. Anatomic variation: Shallow outer patellofemoral groove
    1. Patella prone to sublux or dislocate laterally
  • Symptoms
  1. Anterior Knee Pain
    1. Pain beneath, under or peri-Patellar
    2. Gradually progressive general aching or grating pain
  2. Associated symptoms
    1. Stiffness
    2. Grinding, popping, or clicking sound on knee flexion
  3. Provocative factors
    1. Going up or down stairs, or down hills
    2. Running
    3. Squatting
    4. Kneeling
    5. Prolonged sitting with knee bent (Theater sign)
  4. Giving-way Sensation (reflex response to pain)
    1. Patellofemoral Syndrome is associated with painful giving-way
    2. Contrast with Anterior Cruciate Ligament Tear (ACL Tear) which is associated with painless giving-way
  5. Findings that make alternative diagnosis more likely
    1. No locking or catching (contrast with meniscal tear)
    2. Knee Effusion
    3. Knee Trauma History
  • Signs
  1. Inspection
    1. Excessive pronation (over pronation) on Running gait (pes pronatus)
      1. Medial aspect of shoe is worn down the most
    2. No Knee Effusion
    3. Abnormal Patella alignment and tracking
      1. See Patella Tracking Assessment (J Sign)
      2. Increased Q Angle of the Knee
    4. Lateral knee structures tight
      1. Patella Glide Test
      2. Patella tilt test
    5. Hamstring tightness (predisposing finding)
      1. Passive Knee Extension
  2. Palpation
    1. Tender undersurface of medial or lateral Patella
    2. Crepitation on knee range of motion
  3. Provocative testing
    1. Positive Patellar Apprehension Test
    2. Knee Pain with squatting
  4. Dynamic Valgus
    1. Knee shifts into valgus position on squatting while balancing on the affected leg
  • Differential Diagnosis
  1. See Anterior Knee Pain
  2. Patellar Tendinopathy
    1. Pain and focal tenderness at inferior Patellar pole, especially worse with jumping in Patellar Tendinopathy
    2. Contrast with more generalized Patellar pain, especially descending stairs in Patellofemoral Syndrome
  1. Not indicated in most cases of Patellofemoral Syndrome
    1. Used primarily to exclude other causes of Knee Pain
    2. Consider for refractory symptoms after 8 weeks of management
  2. Indications
    1. Age >50 years
      1. Patellofemoral Osteoarthritis
    2. Child and Adolescent
      1. Osteochondritis Dissecans
      2. Bone Neoplasms
  3. Views
    1. Weight-bearing AP Xray
    2. Weight-bearing lateral Xray
    3. Sunrise (Axial view at 20-45 degrees)
  • Management
  • Medical
  1. Relative rest
    1. Avoid squats and lunges
    2. Reduce Running mileage to painless distance
    3. Cross-train with biking, swimming, eliptical trainer
  2. Pain relief
    1. NSAIDs (variable efficacy)
    2. Ice Therapy
  3. Pelvic-femoral rehabilitation
    1. Patients with dynamic valgus should undergo PT to work hip abduction and external rotation
  4. See Patellofemoral Knee Exercises
    1. OrthoPFSExercises.htm
  5. Quadriceps strengthening
    1. Isometric progressive resistance Exercises
    2. Leg-sled Press (45 degree)
  6. Eccentric Exercises (especially for Jumper's Knee)
    1. Patient stands on wedge platform with toes pointing to the bottom of a down slope
    2. Patient then does standing knee bends to 45 degrees and then fully extends
  7. Lower extremity StretchingExercises
    1. Quadriceps Stretching
    2. Quadriceps strengthening
      1. Do not load knee at more than 45 degrees flexion
      2. Isometric quadriceps strengthening
        1. Sit on floor with affected leg straight and the unaffected leg flexed
        2. Towel roll placed under affected leg (optional)
        3. Extend the knee, pressing the towel downwards and hold for 10 seconds
        4. Repeat 10 repetitions in each of 3 sets
      3. Straight Leg Raise
        1. Sit on floor with affected leg straight and the unaffected leg flexed
        2. Slowly raise the affected leg 8 inches off floor and then return to floor (over 2-4 seconds)
        3. Repeat 10 repetitions in each of 3 sets
    3. Hamstring stretches
      1. Lie supine on floor
      2. Flex the hip to 90 degrees and grasp to hold in position
      3. Knee starts at 90 degrees flexion and is fully extended to 90 degrees for 30-60 seconds
      4. Perform twice for each leg, twice daily
    4. Hip adductor strengthening Exercises
      1. Stand with one foot on platform, step or 2x4 wood
      2. Keep both knees straight and extended
      3. Start with hips and Pelvis level with floor
      4. Allow the unsupported leg to slowly lower, and then raise the leg to original position
      5. Repeat 10 repetitions in each of 3 sets
    5. Iliotibial Band stretches
    6. Ankle stretches
      1. Gastrocnemius Muscle
      2. Soleus Muscle
  8. Shoe modifications
    1. Replace excessively worn Running Shoes
    2. Over-pronators
      1. Running Shoe for over-pronators
      2. Anti-pronation pad
      3. Formal Orthotic
  9. Core Muscle Strength (trunk Exercises)
  10. Avoid provocative factors
    1. Limit weight on a flexed knee
    2. Consider cross-training activity
    3. Reduce mileage and pace
    4. Avoid uphill and downhill Running
  11. Patellar Taping (Kinesiotaping)
    1. Inconsistent evidence of benefit
    2. May offer short term pain relief and improve Patellar tracking when used early in course
    3. Used as an adjunct to physical therapy and Exercises
    4. Wittingham (2004) J Orthop Sports Phys Ther 34:504-10 [PubMed]
    5. Callaghan (2012) Cochrane Database Syst Rev (4): CD006717 [PubMed]
  12. Patellar bracing
    1. Not generally recommended
      1. No significant benefit or inconsistent benefit over Exercises alone
      2. Despite this, use has increased in sports medicine as of 2012
      3. Some runners may see benefit
    2. References
      1. Lun (2005) Clin J Sport Med 15:235-40 [PubMed]
      2. Swart (2012) Br J Sports Med 46(8): 570-77 [PubMed]
  • Management
  • Surgical (under 5-10% of cases)
  1. Indications
    1. Persistent symptoms >6-12 months
    2. Refractory to formal rehabilitation program
    3. Other Knee Pain causes excluded
  2. Procedures
    1. Diagnostic Knee Arthroscopy
    2. Smoothing of Patella articular cartilage
    3. Lateral Release
    4. Patellar tendon relocation
  3. Efficacy
    1. Arthroscopy adds no benefit over home Exercise in Patellofemoral Pain Syndrome
      1. Kettunen (2007) BMC Med 5:38 [PubMed]
  • Course
  1. Course may be prolonged in athletes as long as 6 years
  • References
  1. Arnold (2018) Am Fam Physician 97(8): 510-6 [PubMed]
  2. Childress (2013) Am Fam Physician 87(7): 486-90 [PubMed]
  3. Dixit (2007) Am Fam Physician 75(2):194-204 [PubMed]
  4. Fulkerson (2002) Am J Sports Med 30:447-56 [PubMed]
  5. Gaitonde (2019) Am Fam Physician 99(2): 88-94 [PubMed]
  6. Jones (2015) Am Fam Physician 92(10): 875-83 [PubMed]
  7. Juhn (1999) Am Fam Physician 60(7): 2012-8 [PubMed]
  8. Ruffin (1993) Am Fam Physician 47(1): 185-94 [PubMed]