Patellofemoral Pain

Key Features

Essentials of Diagnosis

• Pain experienced with bending activities (kneeling, squatting, climbing stairs)

• Lateral deviation or tilting of the patella in relation to the femoral groove

General Considerations

• Also known as anterior knee pain, chondromalacia, or "runner's knee," describes any pain involving the patellofemoral joint

• Pain affects any or all of the anterior knee structures, including the medial and lateral aspects of the patella as well as the quadriceps and patellar tendon insertions

• Patellofemoral pain is also associated with muscle strength and flexibility imbalances as well as altered hip and ankle biomechanics

• Abnormal patellar tracking during flexion can lead to abnormal articular cartilage wear and pain

• When the patient has ligamentous hyperlaxity, the patella can sublux out of the groove, usually laterally

• There are two common presentations

  • Patients whose ligaments and patella are too loose (hypermobility)

  • Patients who have soft tissues that are too tight leading to excessive pressure on the joint

Clinical Findings

Symptoms and Signs

• Pain

  • Usually occurs in the anterior knee with bending movements and less commonly in full extension

  • May sometimes be referred to the posterior knee or over the medial or lateral inferior patella

• Symptoms may begin after a trauma or after repetitive physical activity, such as running and jumping

• When maltracking, palpable and sometimes audible crepitus can occur

• Intra-articular swelling usually does not occur unless there are articular cartilage defects or unless osteoarthritis develops

• On physical examination, it is important to palpate the articular surfaces of the patella

• Patellar mobility can be assessed by medially and laterally deviating the patella

  • Deviation by one-quarter of the diameter of the kneecap is consider normal

  • Deviation by greater than one-half of the diameter suggests excessive mobility

Diagnosis

Imaging

• Radiographs may show lateral deviation or tilting of the patella in relation to the femoral groove

• MRI may show thinning of the articular cartilage but is not clinically necessary, except prior to surgery or to exclude other pathology

Diagnostic Studies

• Apprehension sign

  • Suggests instability of the patellofemoral joint

  • Positive when the patient becomes apprehensive when the patella is deviated laterally (Table 41–7)

• Patellar grind test

  • Performed by grasping the knee superior to the patella and pushing it downward with the patient supine and the knee extended, pushing the patella inferiorly

  • The patient is asked to contract the quadriceps muscle to oppose this downward translation, with reproduction of pain or grinding being considered a positive sign for chondromalacia of the patella