Jane, age 42, presents with right knee pain that she’s had for about six months. She denies any trauma. Jane describes the pain as “vague and poorly localized” but worse with activity. She says she started a walking/running program nine months ago, when she was told she was overweight (BMI, 29). She has lost 10 pounds since then and hopes to lose more by continuing to exercise. Further review reveals that Jane has experienced increasing pain while ascending and descending stairs and that the pain is also exacerbated when she stands after prolonged sitting.
If Jane were your patient, what would you include in a physical examination, and how would you diagnose and treat her?
Knee pain is a common presentation in primary care. While traumatic knee pain is frequently addressed in the medical literature, little has been written about chronic nontraumatic nonarthritic knee pain such as Jane’s. Thus, while physical exam tests often lead to the correct diagnosis for traumatic knee pain, there is limited information on the use of such tests to determine the etiology of chronic knee pain.
This review was developed to fill that gap. The pages that follow contain general guidance on the diagnosis and treatment of chronic nontraumatic knee pain. The conditions are presented anatomically—anterior, lateral, medial, or posterior—with common etiologies, history and physical exam findings, and diagnosis and treatment options for each (see Table, page 28).1-31
ANTERIOR KNEE PAIN
Patellofemoral pain syndrome (PFPS)
The most common cause of anterior knee pain, PFPS is a complex entity with an etiology that has not been well described.2 The 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.4,32 A 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.1 Patients 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.2 A 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 50 or older, or no improvement occurs after eight to 12 weeks of treatment.33
Treatment. The most effective and strongly supported treatment for PFPS is a six-week physiotherapy program focusing on strengthening the quadriceps and hip muscles and stretching the quadriceps, ITB, hamstrings, and hip flexors.4,5 There is limited information about the use of 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 nonconclusive. There is a paucity of prospective randomized trials of patellar bracing, and a 2012 Cochrane review found limited evidence of its efficacy.34 But a 2014 meta-analysis revealed moderate evidence in support of patellar taping early on to help decrease pain,6 and 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
When you examine Jane, 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 six weeks of physiotherapy.
Patellofemoral instability (PFI)
PFI occurs when the patella disengages completely from the trochlear groove.11 PFI’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.10,11 Older patients, predominately women, have an increased risk for PFI.9 Patients 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.9 A family history of PFI is common, as well.10
Diagnosis. Patients with PFI often present with nonspecific anterior knee pain secondary to recurrent dislocation.13 Notable exam findings include
• 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. 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.11 However, 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
Patellar tendinopathy
An overuse injury often called “jumper’s knee” because it is associated with high-intensity jumping sports (eg, volleyball and basketball), patellar tendinopathy is an insertional tendinopathy with pain most commonly at the proximal patellar tendon.10 The pathology of the injury, though poorly understood, is believed to result from an impaired healing response to microtears.12,14
Diagnosis. Patients with patellar tendinopathy typically present with anterior suprapatellar pain aggravated by activity. Classically, the pain can occur in any of four phases12
1. Pain isolated after activity
2. Pain that occurs during activity but does not impede activity
3. Pain that occurs both during and after the activity and interferes with competition
4. A complete tendon disruption.
Examination should include an assessment of the patellar tendon for localized thickening, nodularity, crepitus, and focal suprapatellar tenderness. The muscle tendon function should be evaluated by assessing knee mobility and strength of the quads via straight-leg raise, decline squat, or single-leg squats.12 The Victorian Institute of Sport Assessment (VISA) questionnaire can be used to quantify the symptoms and to help track the patient’s progress throughout therapy.31 There are no proven special tests or radiologic studies to aid in the diagnosis of patellar tendinopathy,14 but MRI can be used for further evaluation when findings are equivocal.35
Treatment. A wide range of options, from eccentric training (eg, three sets of 15 repetitions performed twice a day for 12 weeks) and physical therapy to platelet-rich plasma (PRP) injections, sclerosing injections, and surgery, are available for the treatment of patellar tendinopathy.13-15 While no specific data have proven the superiority of any one therapy, expert consensus recommends eccentric exercise as initial therapy, performed for 12 weeks.14,15
It’s also interesting to note that a recently published study showed that three weekly PRP injections helped 75% of patients—all of whom failed to respond to four months of eccentric therapy—return to their presymptom activity level within 90 days.16 Corticosteroid injections should not be used to treat patellar tendinopathy due to the risk for tendon rupture.15 Orthopedic referral for surgical intervention should be considered for patients who fail to respond after three to six months of conservative therapy.14
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