Basics
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 the following:
- Femoral anteversion
- Genu valgus
- Pes planus
- These three 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 one area can lead to secondary stresses at a distant location.
- Excess femoral anteversion, as well as marked pes planus, can contribute to increased lateral pull on the patella and subsequent patellofemoral pain.
- Further contributing factors include a wider pelvis and a more laterally positioned tibial tubercle, both of which also contribute to altered biomechanics at the knee.
- Weak hip abductors and quadriceps muscles and tight hamstrings, iliotibial band, Achilles tendon, and quadriceps can lead to increased forces across the patellofemoral joint.
Diagnosis
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
- Assess one-legged squat for weak hip abductors " knee will go into valgus.
- Palpate medial and lateral patellar facets for areas of pain due to increased contact forces.
- 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 change, which ranges from mild cracking attributed to softening to locking and catching attributed to cartilage disruption.
- There is no single angulation or rotation profile that is universal for all anterior knee pain patients. However, many have femoral anteversion, genu valgus, and pes planus. Weak hip abductors and tight hamstrings or quadriceps may also be found.
Diagnostic Tests & Interpretation
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 preteens
- 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 or posterolateral hemijoint tenderness with knee hyperflexion and rotation
- Distal iliotibial band tendonitis
- Irritation of distal iliotibial band as it rubs over the lateral condyle before attaching on lateral tibia (Gerdy tubercle)
- Common in runners or those with weak hip abductors
- Prepatellar bursitis
- An inflammation of the fluid-filled bursa 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.
Treatment
General Measures
- A progressive exercise program is the main focus of treatment.
- Strength and flexibility exercises are needed to improve the mechanics of the patellofemoral joint.
- Strengthening should include hip abductors, hip extensors, hamstrings, and the quadriceps muscles.
- This strengthening can be performed several times each day as a home exercise program or formally with physical therapy in more recalcitrant cases.
- Stretching should include quadriceps, hamstrings, iliotibial band, and tendoachilles stretches as indicated by the physical examination (PE).
- 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.
Additional Reading
- Collado H, Fredericson M. Patellofemoral pain syndrome. Clin Sports Med. 2010;29(3):379 " 398. [View Abstract]
- Flynn J, Lou J, Ganley T. Prevention of sports injuries in children. Curr Opin Pediatr. 2002;14(6):719 " 722. [View Abstract]
- Ganley TJ, Pill SG, Flynn JM, et al. Pediatric and adolescent sports medicine. Curr Opin Orthopaed. 2001;12:456 " 461.
- Hart L. Supervised exercise versus usual care for patellofemoral pain syndrome. Clin J Sport Med. 2010;20(2):133. [View Abstract]
- Murray KJ. Hypermobility disorders in children and adolescents. Best Pract Res Clin Rheumatol. 2006;20(2):329 " 351. [View Abstract]
Codes
ICD09
- 719.46 Pain in joint, lower leg
- 717.89 Other internal derangement of knee
- 733.92 Chondromalacia
- 736.41 Genu valgum (acquired)
ICD10
- M25.569 Pain in unspecified knee
- M22.2X9 Patellofemoral disorders, unspecified knee
- M22.40 Chondromalacia patellae, unspecified knee
- M21.069 Valgus deformity, not elsewhere classified, unspecified knee
- M22.2X2 Patellofemoral disorders, left knee
- M25.561 Pain in right knee
- M21.061 Valgus deformity, not elsewhere classified, right knee
- M22.2X1 Patellofemoral disorders, right knee
- M25.562 Pain in left knee
- M21.062 Valgus deformity, not elsewhere classified, left knee
SNOMED
- 30989003 Knee pain (finding)
- 202114006 Patellofemoral maltracking (disorder)
- 36071006 chondromalacia of patella (disorder)
- 299330008 knee joint valgus deformity (finding)
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 intra-articular 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 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.