**2.4 Physical examination**

Most patients present to the outpatient clinic in the subacute phase after their injury. Physical examination at this stage may be difficult due to presence of pain and swelling. In select cases, aspiration of a tense joint effusion may be required to relieve pain, and to allow better physical examination and radiographic evaluation. The appearance of the joint aspirate may provide important diagnostic clue. Lipohemarthrosis indicates presence of a concomitant osteochondral fracture.

A complete examination of the injured lower extremity should be undertaken. The astute clinician should look for limb malalignment (especially genu valgum), patella alta, and rotational abnormality, such as excessive anteversion of the femoral neck (internal femoral torsion) and external tibial torsion. A comprehensive ligamentous examination of the injured knee should be performed to rule out associated injury to the cruciate and/or collateral ligaments. Joint-line tenderness and a positive McMurray's test may indicate presence of concomitant meniscal injury. Generalized ligamentous hyperlaxity should be noted by examining finger metacarpophalangeal joint hyperextension, thumb-to-forearm apposition, knee hyperextension, and elbow hyperextension. A complete neurovascular examination of the limb should be performed.

#### **Figure 2.**

*Mechanisms of acute patellar dislocation: (A) A noncontact dislocation occurs by external rotation of the lower leg relative to the body. (B) Contact injury is caused by a direct blow to the medial aspect of the knee. Adapted from Steiner and Parker [30]. Reprinted with permission of The Cleveland Center for Medical Art & Photography © 2008. All Rights Reserved.*

The knee should be specifically palpated for areas of localized, maximal tenderness. There is tenderness along the medial border of the patella and also over the injured or torn medial patellar retinaculum. In some cases, a palpable defect in the medial retinaculum is noted. There may be localized tenderness at the origin, at the insertion, or along the course of the MPFL. Tenderness at the medial border of the patella or along the lateral femoral condyle may suggest osteochondral injury. Tenderness or asymmetry at the distal portion of the vastus medialis obliquus (VMO) may suggest significant disruption of its tendinous insertion. The patellar apprehension test should be performed to determine patellar instability. The apprehension test is performed by applying a laterally directed force along the medial border of the patella with the knee in 20 to 30 degrees of flexion (**Figure 3**). A positive finding occurs when the patient has a sense of pain and impending subluxation or dislocation. In addition to apprehension, there may be increased translation of the patella when compared with the uninjured knee.

#### **2.5 Associated injuries**

The most common findings associated with acute dislocation of the patella are chondral and osteochondral injuries. Stefancin and Parker [31] systematically reviewed the literature on patients who had had first-time patellar dislocation. The average age of the patients was 21.5 years. In their compilation of 70 articles, the incidence of osteochondral fracture (confirmed by open surgery, arthroscopy, or MRI) ranged from 0% to 73%, with an overall incidence of 24%. Osteochondral injuries resulting from lateral patellar dislocation have a characteristic pattern; there is an injury to the medial facet of the patella and the lateral femoral condyle. The osteochondral fragments may remain attached, may become loose in the joint, or may be retained in the peripatellar retinacular tissue [30].

#### **2.6 Radiographic studies**

The radiographic evaluation of patients with patellar dislocation include plain radiographs and MRI of the knee.

The plain radiograph series of the knee should include standing anterior–posterior view, 45-degree flexion posterior–anterior weight-bearing view (Rosenberg view), lateral view, and axial view. The lateral view provides useful information

#### **Figure 3.**

*Patellar apprehension test. The physician applies a lateral force to the medial border of the patella with the knee in 20 to 30 degrees of flexion. The patient experiences a sensation of the patella subluxating or dislocating in an outward (lateral) direction. Adapted from Steiner and Parker [30]. Reprinted with permission of The Cleveland Center for Medical Art & Photography © 2008. All Rights Reserved.*

about the patellar height, trochlear depth, and patellar tilt. Patella alta is a known risk factor for patellar dislocation and can be determined on the lateral radiograph by numerous methods. These methods include the Insall-Salvati ratio [32], the modified Insall-Salvati ratio [33], the Blackburne-Peel ratio [34], and the Caton-Deschamps ratio [35]. A brief description of the above-mentioned radiographic measurements is provided under the heading – Assessment of Patellar Height – in Section 3 of this book chapter.

The Blackburne-Peel ratio, which is based on consistent bony landmarks, is the most reproducible and has the most moderate results for classification into patella alta and patella baja. The trochlear depth and patellar tilt can also be determined from the lateral radiograph of the knee. It is worth emphasizing that the lateral view of the knee must be a "true" lateral with the posterior borders of the femoral condyles overlapping for accurate interpretation and analysis of the trochlear depth and patellar tilt. The axial views as described by Merchant and colleagues [36] and Laurin and colleagues [37, 38] are commonly used. The axial view of the patellofemoral joint provides valuable information about any persistent subluxation or dislocation of the patella. In addition to the lateral patellar overhang, the sulcus angle can be determined on the axial view.

MRI has become the imaging modality of choice in the evaluation of patients with acute dislocations of the patella. Various pathologies such as, VMO edema, bone contusion, chondral and osteochondral injury, loose body, medial patellar retinacular injury, MPFL injury, and associated ligamentous and/or meniscal injury can be well visualized on a high-quality MRI study. The MPFL is almost universally disrupted in patients with acute lateral dislocation of the patella. The aforementioned MRI findings following acute dislocation of the patella are useful for the treating physician and allows him/her to formulate a sound treatment plan. Presence of a large osteochondral fragment, loose body, a complete tear of the MPFL, and associated ligamentous or meniscal injury may point the surgeon toward operative intervention [30].

#### **2.7 Nonoperative treatment**

Currently, there exists a debate in the orthopedic literature regarding nonoperative versus operative treatment of acute patellar dislocations. Most physicians recommend a more conservative, i.e. nonoperative approach, whereas some recommend immediate repair of the injured medial structures.

Maenpaa and Lehto [39] have reported a long-term study on nonoperative treatment of acute patellar dislocations. In their study, 100 patients were treated nonoperatively for primary acute patellar dislocations, either by plaster cast (N = 60); by posterior splint (N = 17); or by patellar bandage or brace (N = 23) for 2 to 4 weeks, followed by rehabilitation. Follow-up examinations were performed at an average of 13 years (range, 6 to 26 years) after the initial injury. The recurrence rate was 44% overall, yielding 0.17 redislocations per follow-up year; an additional 19% without recurrence had continued symptoms of pain and instability, and required surgery. The mean Kujala score at follow-up was 80, with significantly lower scores in those older than 30 years of age.

In the management of acute patellar dislocations, prospective, randomized controlled studies have shown higher Kujala scores (higher scores indicate better knee function) [40–42] and reduced rate of recurrent patellar dislocation [40–43] after surgical stabilization as compared with nonoperative treatment.

Despite above-mentioned studies, majority of patients with acute lateral dislocation of the patella are initially treated by nonoperative management. Nonoperative treatment is indicated for patients with acute, first-time dislocation of the patella without associated osteochondral fracture or loose bodies. The nonoperative treatment consists of immobilization in a plaster cast or a brace for about 4–6 weeks followed by a period of well-planed, supervised rehabilitation. Immobilization allows for healing of the injured soft tissues on the medial aspect of the knee. Some surgeons recommend early rehabilitation of the knee without immobilization to avoid harmful effects of immobilization (such as quadriceps weakness and wasting, knee stiffness, and chondrolysis). Whether immobilized or not, patients with acute patellar dislocation should expect a prolonged rehabilitation period before return to sport.

#### **2.8 Operative treatment**

Operative treatment is indicated for patients who have persistent pain, recurrent instability and diminished knee function, and who have failed a trial of nonoperative management. In our experience, the indications for initial operative treatment include presence of an osteochondral fragment, loose body, a complete tear or avulsion of the MPFL, palpable defects in the vastus medialis insertion, obvious

#### *Patellofemoral Instability DOI: http://dx.doi.org/10.5772/intechopen.99562*

tear in the medial patellar retinaculum, associated ligamentous or meniscal injury, and persistent asymmetric subluxation of the patella.

The surgical procedures include arthroscopy, lateral release, medial retinacular repair, MPFL repair with or without augmentation, realignment procedure, or combination of these surgical techniques. Repair and reconstruction should be undertaken to address identifiable, injured soft tissues on the medial aspect of the knee, whereas release or lengthening of the lateral patellar retinaculum should be performed to restore soft tissue balance of the patellofemoral joint. Realignment procedure is indicated for patients who have a clear underlying anatomic malalignment.

### *2.8.1 Arthroscopy*

Arthroscopy helps to identify and treat the associated intra-articular pathologies, such as chondral and osteochondral injuries; meniscal tears; and ligamentous injuries. Arthroscopy can be performed alone or in combination with open procedures. Minor or small chondral or osteochondral fragments can be excised, and medium-sized or large chondral or osteochondral fragments can be fixed with the use of modern arthroscopic surgical technique, instrumentation, and implants.

## *2.8.2 Lateral release*

We are extremely cautious in advocating an isolated lateral patellar retinaculum release procedure for the treatment of acute lateral dislocation of the patella. In our opinion, arthroscopic lateral release is strictly indicated for patients who have a documented patellar tilt without subluxation. Using a biomechanical cadaveric model, Desio et al. [8] have shown that the intact lateral patellar retinaculum actually prevents lateral displacement of the patella, contributing 10% of the restraining force. Several authors [44–46] have reported recurrent lateral dislocations of the patella, almost exclusively in groups of patients treated by lateral release. Moreover, iatrogenic medial subluxation and dislocation of the patella following lateral release have been reported by several authors [47, 48]. Fithian et al. [49] conducted a scientific survey of the International Patellofemoral Study Group to determine current views regarding lateral patellar release. The survey response rate was 60%. Isolated lateral release was estimated to account for only 1 to 5 surgical cases per respondent per year, or 2% of cases performed annually. The results of the survey showed that only 7% of respondents would consider a lateral release in a first-time lateral patellar dislocation with a tight lateral retinaculum, and 37% would consider a history of lateral patellar dislocation as a contraindication to lateral release procedure. The authors concluded that even among experienced knee surgeons with a special interest in disorders of the patellofemoral joint, isolated lateral release is rarely performed. Strong consensus was found that isolated lateral release should not be undertaken without previous planning in the form of objective clinical indications and preoperative informed consent. Therefore, in view of the above-mentioned findings, we emphasize that lateral release procedure should be used with caution in patients with acute lateral dislocation of the patella.

#### *2.8.3 Medial retinacular repair*

Disruption or stretching of the medial patellar retinaculum and MPFL almost always accompanies lateral dislocation of the patella. Hence, the mainstay of early surgical treatment in the acute, first-time patellar dislocation is repair or reefing of the injured medial soft tissue structures, often accompanied by a lateral release procedure.

## *2.8.4 Medial patellofemoral ligament repair and augmentation*

Repair or reefing of the medial retinaculum often does not completely address the medial-sided pathology after acute lateral dislocation of the patella [30]. As mentioned previously, the MPFL is injured in about 90% of patients who sustain acute lateral dislocation of the patella. Therefore, it is logical that patellar stability may be restored by undertaking direct repair of the MPFL with or without augmentation (using a strip of fascia, slip of the medial patellar retinaculum, distal adductor magnus tendon, etc.). However, there is a limited clinical evidence showing the efficacy of such techniques. Going forward, high-quality, prospective randomized clinical studies utilizing a larger population are needed to firmly establish the role of MPFL repair and augmentation in patients with acute lateral dislocation of the patella. In contrast, MPFL reconstruction is a fairly well-established surgical technique and is usually reserved for cases of recurrent patellofemoral instability. A detailed discussion on MPFL reconstruction is provided in Section II of this chapter.

### **2.9 Rehabilitation**

Traditionally and historically, nonoperative treatment has been the mainstay of therapy for patients with acute patellar dislocation. A comprehensive, wellplanned supervised rehabilitation program is vital for a successful outcome. The initial goals of rehabilitation are to decrease joint effusion, regain both active and passive range of motion, and advance the weight-bearing status of the extremity. In the next phase, closed kinetic chain exercises, quadriceps strengthening, and proprioceptive exercises are begun. In the last phase of rehabilitation, emphasis is placed on proprioceptive feedback, and functional and sport-specific training [30]. Isokinetic, eccentric, and high-torque exercises can cause high articular cartilage pressures and should be avoided [50]. Core strengthening is emphasized. In addition, gluteal muscle strengthening should be undertaken to improve the external rotators of the hip, thus externally rotating the femur and decreasing the Q-angle. The ultimate goal of rehabilitation is to obtain a pain-free, mobile, stable and functional knee.

The patient is allowed to return to play when the following criteria have been met: Subjectively, there should be no pain, swelling, or sensation of giving-way/instability. Objectively, there should be no joint effusion, no tenderness, a negative patellar apprehension test, and a full, pain-free range of motion in the knee [30]. Quadriceps strength in the affected lower extremity should be at least 80% as compared with the contralateral side. The role and usefulness of patellar bracing and taping in the management of acute patellar dislocation is unclear. Patellofemoral instability symptoms may be reduced in some patients with a patellar cutout brace or patellar taping. Although patellar taping was originally reported to have a high success rate, researchers have been unable to reproduce these results [51]. Patellar bracing and/or taping should be regarded as adjuvants to physical therapy. Patient should be counseled regarding expectations and clinical outcomes of the nonoperative and operative treatment.

#### **2.10 Summary**

• There are two distinct groups of patellar dislocations; one group of patients with normal anatomy and a traumatic event, and the other group with predisposing anatomical factors and a history of patellar subluxation or dislocation without a traumatic event [30].

	- 1.Presence of an osteochondral fracture or major chondral injury.
	- 2.Substantial disruption of the medial soft tissue patellar stabilizers (medial retinaculum and MPFL).
	- 3.A persistent laterally subluxed patella.
	- 4.Recurrent, symptomatic lateral patellar subluxation or dislocation.
	- 5.Failure of a trial of nonoperative management.
