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Nontraumatic Knee Pain: A Diagnostic & Treatment Guide

Clinician Reviews. 2014 December;24(12):720-728

References

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Anterior knee pain

Patellofemoral pain syndrome

Patellofemoral pain syndrome is the most common cause of anterior knee pain. Taping or bracing—along with physical therapy—may help reduce the pain. Patellofemoral pain syndrome (PFPS), the most common cause of anterior knee pain, is a complex entity with an etiology that has not been well described.²The quadriceps tendon, medial and lateral retinacula, iliotibial band (ITB), vastus medialis and lateralis, and the insertion of the patellar tendon on the anterior tibial tubercle all play a role in proper tracking of the patellofemoral joint; an imbalance in any of these forces leads to abnormal patellar tracking over the femoral condyles, and pain ensues. PFPS can also be secondary to joint overload, in which excessive physical activity (eg, running, lunges, or squats) overloads the patellofemoral joint and causes pain.

Risk factors for PFPS include strength imbalances in the quadriceps, hamstring, and hip muscle groups, and increased training, such as running longer distances.^4,32A recent review showed no relationship between an increased quadriceps (Q)-angle and PFPS, so that is no longer considered a major risk factor.⁵

Diagnosis. PFPS is a diagnosis of exclusion, and is primarily based on history and physical exam. Anterior knee pain that is exacerbated when seated for long periods of time (the “theater sign”) or by descending stairs is a classic indication of PFPS.¹Patients may complain of knee stiffness or “giving out” secondary to sharp knee pain and a sensation of popping or crepitus in the joint. Swelling is not a common finding.²

A recent meta-analysis revealed limited evidence for the use of any specific physical exam tests to diagnose PFPS. But pain during squatting and pain with a patellar tilt test were most consistent with a diagnosis of PFPS. (The patellar tilt test involves lifting the lateral edge of the patella superiorly while the patient lies supine with knee extended; pain with <20° of lift suggests a tight lateral retinaculum). Conversely, the absence of pain during squatting or the absence of lateral retinacular pain helps rule it out.²A physical exam of the cruciate and collateral ligaments should be performed in a patient with a history of instability. Radiography is not needed for a diagnosis, but may be considered if examination reveals an effusion, the patient is age 50 years or older, or no improvement occurs after 8 to 12 weeks of treatment.³³

Treatment. The most effective and strongly supported treatment for PFPS is a 6-week physiotherapy program focusing on strengthening the quadriceps and hip muscles and stretching the quadriceps, ITB, hamstrings, and hip flexors.^4,5There is limited information about the use of nonsteroidal anti-inflammatory drugs (NSAIDs), but they can be considered for short-term management.²

Patellar taping and bracing have shown some promise as adjunct therapies for PFPS, although the data for both are non-conclusive. There is a paucity of prospective randomized trials of patellar bracing and a 2012 Cochrane review found limited evidence of its efficacy.³⁴But a 2014 meta-analysis revealed moderate evidence in support of patellar taping early on to help decrease pain,⁶and a recent review suggests that it can be helpful in both the short and long term.⁷

Taping or bracing may be useful when combined with a tailored physical therapy program. Evidence for treatments such as biofeedback, chiropractic manipulation, and orthotics is limited, and they should be used only as adjunctive therapy.⁴

CASE › When you examine Ms. T, you find no swelling of the affected knee. You perform the tilt test, which elicits pain. Squatting causes some pain, as well. You diagnose PFPS and provide a referral for 6 weeks of physiotherapy.

Patellar subluxation or chronic dislocation

Patellofemoral instability (PFI) occurs when the patella disengages completely from the trochlear groove.¹¹PFI’s etiology also relates to the complexity of the patellofemoral joint. Here, too, stability of the joint is achieved with a combination of soft tissue and bony restraints. At full extension and early flexion of the knee, however, the mechanisms of stability are limited, resulting in increased instability. Other associated factors include Q-angle, lateral pull from a tight ITB, and opposing forces from the vastus lateralis and vastus medialis obliquus (VMO).^8-10

Risk factors for PFI. The most common predisposing factors for PFI are trochlear dysplasia, patella alta, and lateralization of the tibial tuberosity or patella.^10,11Older patients (mostly women) have an increased risk for patellofemoral instability. Older patients, predominately women, have an increased risk for PFI.⁹Patients usually have a history of patellar subluxation or dislocation in their youth, with approximately 17% of those who had a first dislocation experiencing a recurrence.⁹A family history of PFI is common, as well.¹⁰

Diagnosis. Patients with PFI often present with nonspecific anterior knee pain secondary to recurrent dislocation.¹³Notable physical exam findings are:

a positive J sign (noted if the patella suddenly shifts medially during early knee flexion or laterally during full extension)
decreased quadriceps (specifically VMO) and hamstring strength and flexibility
patellar hypermobility, which should be no more than a quarter to a half of the patellar diameter bilaterally
pain during a patellar tilt test 
a positive patellar apprehension test.¹⁰(With the patient lying with the knee flexed to 20°, place thumbs on the medial patella and push laterally; the patient will straighten leg with pain or “apprehension” prior to patellar dislocation.)

Plain radiography should be ordered in all cases to assess for osseous trauma/ deformity and to help guide surgical consideration. Magnetic resonance imaging (MRI) can provide additional information when significant soft tissue damage is suspected or the patient does not improve with conservative therapy.^8,11

Treatment. A recent Cochrane review showed that conservative treatment (VMO strengthening, bracing, and proprioceptive therapy) prevented future dislocations more effectively than surgical intervention.¹¹However, surgery is indicated when obvious predisposing anatomic conditions (osteochondral fracture, intra-articular deformity, or a major tear of a medial soft tissue stabilizer) are clearly shown on imaging.^8,11

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