A Review Paper The Diagnosis and Initial Treatment of Patellofemoral Disorders Alan C. Merchant, MD, MS, John P. Fulkerson, MD, and Wayne Leadbetter, MD Abstract Take-Home Points Our purpose is to provide simple guidelines for the diagnosis ◾ Patellofemoral disorders should be classi- and early care of patellofemoral disorders. Any clinician who fied and diagnosed according to specific treats knee problems, including family practitioners, rheuma- diagnostic categories (eg, lateral patellar tologists, orthopedic surgeons, or physical therapists, must compression syndrome) based on etiolo- know how to make the correct diagnosis, or at least a pre- gy rather than nondescriptive terminology (eg, internal derangement, patellofemoral sumptive diagnosis, at the initial visit. This can avoid unneed- pain syndrome). ed and costly tests, ineffective treatment, and even dam- ◾ Patellofemoral dysplasia defines a aging exercises and unnecessary surgery. The diagnosis of spectrum of abnormalities ranging from patellofemoral disorders is confusing because they can have the mild lateral patellar compression many causes. That is, the etiology of patellofemoral disorders syndrome to the severe recurrent patellar is multifactorial. dislocation. To dispel this confusion and simplify the process, we use ◾ There is an inverse relationship between a clinical classification based on etiology. Within that frame- patient activity level and underlying pa- tellofemoral dysplasia. This relationship de- work are 7 key abnormalities or factors that can cause both termines threshold levels for each patient patellofemoral pain and instability: vastus medialis obliquus becoming symptomatic. deficiency, medial patellofemoral ligament laxity, lateral reti- ◾ Patients should be examined for 7 physi- naculum tightness, increased quadriceps angle, hip abductor cal abnormalities, and if present, in what weakness, patella alta, and trochlear dysplasia. severity. These 7 are: vastus medialis At the initial evaluation, the clinician can assess for these obliquus deficiency, medial patellofem- oral ligament laxity, lateral retinaculum abnormalities through history-taking, physical examination, tightness, increased quadriceps angle, and standard radiography. Any abnormalities identified, hip abductor weakness, patella alta, and along with their severity, can be used to arrive at a diagnosis, trochlear dysplasia. or a presumptive diagnosis, and begin early nonoperative ◾ Advanced imaging is rarely, if ever, need- treatment. The clinician does not need magnetic resonance ed to make a diagnosis or to formulate an imaging at this point, unless a presumptive diagnosis cannot initial treatment plan for these common be made or a more complex problem is suggested. patellofemoral disorders. o diagnose any disease or disorder implies disorders, we use a clinical classification based on an understanding of the condition’s cause(s), etiology. This system’s defined diagnostic cate- Twhich should then lead to a logical treatment gories are useful in identifying probable cause(s), plan. For all too long, however, the diagnosis and which can be appropriately evaluated and treated treatment of patellofemoral disorders have been (Table).1 In simple terms, the philosophy of this hampered by diagnoses that lack specific defini- approach is to try to find out what’s wrong, and try tions based on etiology. A few of these are: inter- to fix it! nal derangement, chondromalacia patellae, patellar This clinical classification provides a frame- maltracking, and patellofemoral pain syndrome. work for common patellofemoral conditions that To simplify the diagnosis of patellofemoral are more easily diagnosed, yet is intentionally Authors’ Disclosure Statement: The authors report no actual or potential conflict of interest in relation to this article. 68 The American Journal of Orthopedics ® March/April 2017 www.amjorthopedics.com Table. Clinical Classification of Patellofemoral Disordersa I. Trauma (conditions caused by trauma in otherwise normal knee) incomplete omitting rare conditions (eg, tumors, A. Acute trauma metabolic bone disease, neurologic conditions). 1. Contusion This allows the focus to fall on the common and 2. Fracture frequently misunderstood causes for patellofem- a. Patella b. Femoral trochlea oral pain and instability. In this article, we address c. Proximal tibial epiphyses (tubercle) patellofemoral dysplasia (section II of the Table) and 3. Patellar dislocation (uncommon in normal knee) 4. Rupture its classification relating to initial evaluation and a. Quadriceps tendon early treatment. This entity defines a spectrum of b. Patellar tendon abnormalities, ranging from the mild lateral patellar B. Repetitive trauma (overuse syndromes) compression syndrome (LPCS) to the moderate 1. Patellar tendinitis (“jumper’s knee”) chronic subluxation of the patella (CSP) and severe 2. Quadriceps tendinitis recurrent dislocation of the patella (RDP). Each pre- 3. Peripatellar tendinitis (eg, anterior knee pain in adolescents, caused by hamstring contracture) sumptive diagnosis is suggested by the patient’s 4. Prepatellar bursitis (“housemaid’s knee”) history and confirmed by physical examination and 5. Apophysitis a. Osgood-Schlatter disease radiography. Computed tomography (CT), magnetic b. Sinding-Larsen-Johansson disease resonance imaging (MRI), and other advanced C. Late effects of trauma imaging modalities are seldom needed to establish 1. Posttraumatic patellar chondrosis a working diagnosis and an initial treatment plan, 2. Posttraumatic patellofemoral arthrosis though they can be important in operative planning 3. Anterior fat pad syndrome, Hoffa syndrome (posttraumatic fibrosis) for complex cases. 4. Reflex sympathetic dystrophy of patella 5. Patellar osseous dystrophy 6. Acquired patella infera Patellofemoral Dysplasia 7. Acquired quadriceps fibrosis Patellofemoral dysplasia (or extensor mechanism II. Patellofemoral dysplasia (or extensor mechanism malfunction) malfunction) is a cluster of physical abnormalities A. Lateral patellar compression syndrome relating to the patellofemoral joint that vary from 1. Secondary patellar chondrosis mild to severe and affect the normal function of 2. Secondary patellofemoral arthrosis that joint. As such, patellofemoral dysplasia itself B. Chronic subluxation of patella should be considered on a continuum of mild to 1. Secondary patellar chondrosis severe. To simplify the diagnosis, the clinician 2. Secondary patellofemoral arthrosis should systematically identify these factors and C. Recurrent dislocation of patella their severity. Armed with this information, the 1. Associated fractures clinician can make the diagnosis and formulate a a. Osteochondral (intra-articular) logical treatment plan for each individual patient. b. Avulsion (extra-articular) 2. Secondary patellar chondrosis This article focuses on 7 physical abnormalities 3. Secondary patellofemoral arthrosis that are most likely developmental and that can be D. Chronic dislocation of patella identified through physical and radiologic examina- 1. Developmental tion. When and how each patient with patellofem- 2. Acquired oral dysplasia becomes symptomatic are deter- III. Idiopathic patellar chondrosis mined by 2 key factors: patellofemoral dysplasia IV. Osteochondritis dissecans severity and activity level (sedentary to strenuous), in an inverse relationship (Figure 1).2 Their complex A. Patella interplay determines when a patient exceeds the B. Femoral trochlea “envelope of function”3 and passes from asymp- V. Synovial plicae (anatomical variants made symptomatic by acute or tomatic to symptomatic. repetitive trauma) A. Pathologic medial patellar plica (“shelf”) Seven Key Patellofemoral Physical Abnormalities B. Pathologic suprapatellar plica Of the 7 commonly identified physical abnormalities C. Pathologic lateral patellar plica that affect the normal functioning of the patellofem- VI. Iatrogenic disorders oral joint, 5 are discovered by physical examination and 2 by radiography; CT and MRI are seldom A. Iatrogenic medial patellar compression syndrome needed in the initial evaluation. The most accurate B. Iatrogenic recurrent medial subluxation of patella and objective method should be used to assess the C. Iatrogenic patella infera presence and severity of each abnormality. aModified fromArthroscopy .1 www.amjorthopedics.com March/April 2017 The American Journal of Orthopedics ® 69 The Diagnosis and Initial Treatment of Patellofemoral Disorders abnormality, with the right knee always recorded Competitive sports first (R/L). For example, severe left MPFL laxity is recorded as 0/3. Numerical values (eg, Q angles) can be directly recorded in this manner: 14°/23°. 1. Vastus Medialis Obliquus Deficiency Symptomatic VMO deficiency is best seen as the sitting patient T h actively maintains the unsupported foot and leg at re sh Activity Level Activity o 30° knee flexion. Normally, the VMO inserts into ld the upper half or third of the medial edge of the Asymptomatic patella; a deficient VMO inserts higher into the me- Sedentary dial edge of the quadriceps tendon, or it is absent and leaves a characteristic hollow at the medial Mild Severe 4 Patellofemoral Dysplasia edge of the patella (Figure 2). Studies using ultrasonography and CT have found significant cor- relations between VMO abnormalities and anterior Figure 1. Diagram shows inverse relationship between severity of patellofemoral dys- plasia and patient activity level. Relationship determines when any given patient will knee pain.5,6