History
Patients with patellofemoral arthritis typically present with anterior knee pain. The patient should be asked the following questions:
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How long has the pain been present?
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What makes it worse?
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Is the condition aggravated by prolonged squatting, stair climbing, or other activities?
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Is the pain dull and achy or is it sharp?
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Have you sought treatment for this condition in the past?
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Why are you seeking treatment now?
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Has there been a recent change in your activity?
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What type of work do you do?
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What other types of activities do you participate in (eg, gardening, kneeing at church, yoga, cycling)
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Have you noticed swelling in the knee?
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Have you had prior knee surgeries?
Pain from arthritis and malalignment is typically variable, becoming worse with activity. Constant pain that does not vary with activity suggests a referred or nonmechanical origin.
Isolated patellofemoral arthritis may cause anterior knee pain that worsens with stair climbing or when rising from a seated position and is not present with other activities, such as walking or running on level surfaces.
Patella instability is associated with intermittent sharp pain at the kneecap. A feeling of "giving way" may be related to muscle weakness or to instability. Recurrent patellar subluxation or dislocation may cause an acute osteochondral fracture or chronic cartilage damage as a result of repeated microtrauma.
Physical Examination
The physical examination comprises observation, measurement, and palpation.
Observation
Astute observations of gait and of lower-extremity alignment are an essential component of the physical examination. Leg-length discrepancies, Q angle, and torsional deformities of the femur, tibia, and foot should be noted. Flexion contractures of the limb should be noted.
Gait, such as waddling gait, should be observed carefully, with the patient not wearing shoes. Excessive pronation of the feet, patella tracking, and rotation of the lower limb should be observed. Muscle tone and atrophy of the quadriceps and hamstrings should be assessed. Patella tracking with passive flexion and extension and with very careful semisquatting should be determined.
A study by Crossley et al found that, compared with normal controls, people with patellofemoral joint osteoarthritis demonstrated the following differences while walking [18] :
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Greater anterior pelvic tilt throughout the stance phase,
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Greater lateral pelvic tilt (ie, pelvis lower on the contralateral side)
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Greater hip adduction
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Lower hip extension during the late stance phase
Physical findings must be evaluated in the context of patient complaints. A study of 210 adults with asymptomatic knees revealed abnormal radiographic or physical examination findings in 95% of women and 79% of men. [19] Patellar crepitus, a hypermobile patella, and lateral position of the patella on the axial radiographs were common in this group of patients. Unfortunately, no long-term follow-up was performed to determine whether subjective complaints developed; however, these findings emphasize the point that a diagnosis cannot be based on physical findings alone.
Measurement
Measurements should be taken of femoral anteversion, knee valgus, tibial pronation, lower limb length, and Q angle.
Limb length is measured from anterior iliac spine to the medial malleolus. Length discrepancies should be noted.
The Q angle is the angle between an imaginary line extending from the anterior superior iliac spine to the patella and a line from the patella through the shaft of the tibia. Normal values are less than 20°. Women typically have larger Q angles than men because of their wider hips. While an association is thought to exist between varus knee alignment and the development of osteoarthritis, no study has ever definitively linked Q angles to knee pathology.
Palpation
A thorough examination of both the affected and nonaffected knees should be performed. The presence of crepitus is nonspecific. A standard knee examination should be performed. Passive and active range of motion should be recorded. Strength and tightness of hamstring and quadriceps muscle groups should be determined.
Assess for the presence of ligamentous laxity, instability, and patella maltracking and attempt to elucidate the source of pain. The goal of palpating the structures of the anterior knee is to determine whether the patient's complaints are related to arthritic changes or to the underlying soft tissues. [20] Attention should be focused on the lateral retinaculum, the quadriceps and patellar tendons, and the quadriceps muscle.
The patella is compressed as the patient flexes the knee. Pain often is elicited by this maneuver if arthritis is present. Resisted knee extension also may reproduce the patient's symptoms in arthritic conditions.
Attempt to laterally displace the patella with the knee in extension. Patients with instability contract their quadriceps muscles or complain of pain because of the feeling of subluxation
Knee stability to varus and valgus stress should be assessed. Stability of the ACL can be determined by anterior drawer and Lachman tests. The stability of the patella to medial and lateral stress should be determined, as should the lateral patella tilt.
The patella normally enters the trochlea from a lateral position and becomes centralized with increasing knee flexion, traveling in a J pattern. Abnormalities observed include excessive lateral tracking increasing the angle at which the patella enters the trochlea.
Perform a hip and spine examination. Additionally, look for a prominent superolateral patellalike bipartite patella or a high-riding patella.
Patellar tendinitis, which is swelling at the inferior pole of the patella tendon, is also a possibility and must be evaluated.
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Patellofemoral arthritis. The sulcus angle is the angle formed by the condyles and the sulcus. This is a measurement of trochlear depth. A finding greater than 138° indicates the presence of patellofemoral dysplasia.
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Patellofemoral arthritis. The patellofemoral index is the ratio of M, the closest distance between the articular ridge and the medial condyle, and L, the closest distance between the lateral facet and condyle.
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Patellofemoral arthritis. The lateral patellofemoral angle is the angle between the intercondylar line and the lateral facet.
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Patellofemoral arthritis. The Insall-Salvati ratio is used to assess the position of the patella and determine if the patella alta or patella baja is present. The ratio of the height of the patella to the length of the patella tendon should be 1:1.
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Patellofemoral arthritis. Anteroposterior, lateral, and patellar views of an arthritic knee demonstrate severe patellofemoral arthritis. This patient subsequently underwent total knee arthroplasty.
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Patellofemoral arthritis. Poor bone quality of the patella made a patella resurfacing procedure impossible in this patient who underwent total knee arthroscopy for severe arthritis.
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Patellofemoral arthritis. This patient had severe medial compartment arthritis but a relatively normal patellofemoral joint. Therefore, patellofemoral resurfacing was not performed at the time of surgery.
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Patellofemoral arthritis.
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- Overview
- Presentation
- DDx
- Workup
- Treatment
- Approach Considerations
- Conservative Management
- Surgical Therapy Overview
- Arthroscopy
- Procedures to Correct Malalignment
- Cartilage Transplantation
- Patellectomy
- Patellofemoral Arthroplasty
- Total Knee Arthroplasty
- Partial Lateral Facetectomy
- Surgical Follow-up
- Complications of Surgery
- Surgical Prognosis
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- Medication
- Questions & Answers
- Media Gallery
- References
