Knee Arthritis

History

A thorough history will rule out systemic causes of pain, such as rheumatoid or other inflammatory arthritides, as well as referred hip pain or radiating pain resulting from degenerative disk disease. Patients with knee OA usually present with pain. Other symptoms include catching, locking, swelling, and decreased motion. Instability is a frequent complaint, but in general it represents quadriceps weakness rather than true ligamentous instability. Patients with chronic ACL deficiency in whom medial compartment gonarthrosis with subsequent varus deformity has developed may experience pain and/or instability. However, in these patients pain is the most common presenting symptom, and instability may not be present as a result of the constraint acquired through the degenerative process and the development of a “cupula” from posteromedial tibial wear. Table 104.1 outlines key questions for patients presenting with knee OA.

Physical Examination

A systematic approach to the physical examination of the knee includes inspection, palpation, range of motion (ROM), and special tests when appropriate. A comparison of the affected and nonaffected limbs, an examination of the joints above and below the affected knee, and an assessment of the patient's distal neurovascular status are routine components of the physical examination.

The inspection begins with an evaluation of limb alignment both while the patient is standing and walking. Varus, valgus, or neutral alignment is noted, as well as an antalgic or Trendelenburg gait or a thrust (i.e., a dynamic change in the deformity with weight bearing). If possible, the patient should perform a full squat and the duck walk (Childress sign). Pain with either or both of these activities suggests a meniscal tear. Any previous incisions should be noted.

With the patient seated and his or her knees flexed over the edge of the table, patellar position and quadriceps asymmetry, if present, are determined. Quadriceps reflex inhibition due to knee injury and effusion frequently leads to quadriceps atrophy.

An effusion, which is characterized by asymmetry in the peripatellar groove on either side of the patella, is confirmed with the swipe test. This test is performed with the patient in the supine position with his or her legs extended and relaxed. The examiner strokes the medial side starting just below the joint line and moves toward the suprapatellar pouch and then does the same on the lateral side while observing for a fluid-wave bulge medially. The presence of a fluid wave indicates a positive swipe test and confirms a small to medium intracapsular effusion.

The patellar ballottement test identifies a moderate to severe effusion. With the knee in full extension, the examiner compresses the patella toward the trochlea and then releases it. If fluid is present, the patella will feel as if it were floating.

Palpation of the knee structures is performed in a methodical fashion and guided by the suspected diagnosis. The temperature of the knee to touch is compared with that of the opposite knee. Increased warmth suggests the presence of inflammation. It is important to determine the point of maximal tenderness. Generally the area anticipated to be most tender is palpated last, so that the patient will not be guarding during the remainder of the examination.

ROM compared with the contralateral knee is measured. Patellar tracking during ROM is palpated, as well as crepitus (a palpable grating sensation) during flexion and extension, with particular attention to its specific location. Finally, the patient is asked to perform a straight leg raise to assess quadriceps strength and extensor mechanism function.

Special tests are then performed, including an assessment of cruciate and collateral stability (see Chapter 90 ). These tests are particularly important to detect the presence of a chronically deficient ACL.

Imaging

Radiographs taken during weight bearing are the gold standard for imaging any knee condition, especially OA. The standard radiographic knee series includes the following views: bilateral standing anteroposterior (AP), bilateral standing 45-degree posteroanterior (PA) flexion, and lateral and skyline of the affected knee. The specific purpose of the two standing films is to identify joint space narrowing compared with the nonaffected knee.

The weight-bearing 45-degree PA flexion radiograph was first described by Rosenberg et al. in 1988 and is often referred to as the Rosenberg view ( Fig. 104.1 ). The authors noted that some patients for whom no joint space narrowing was visible on standing full-extension AP views often were found to have areas of significant cartilage wear at the time of arthroscopy. As the knee is flexed during the stance phase of gait, the femorotibial contact area moves posteriorly and decreases in size, so that force per unit area loading of the knee is increased. Therefore the flexed knee is much more susceptible to chondral damage and subsequent OA. Furthermore, in patients with ACL deficiency, the altered knee biomechanics lead to increased posteromedial wear, particularly on the tibia. For these reasons, the Rosenberg view has better sensitivity and specificity than the conventional standing AP radiograph in detecting joint space narrowing and OA.

If joint space narrowing is observed on the standard knee series, a standing hip to ankle radiograph should be obtained to assess limb alignment ( Fig. 104.2 ). This view is critical for decision-making and surgical planning. A line from the center of the hip to the center of the ankle defines the mechanical axis in the coronal plane. This line generally passes through the center of the knee in a neutrally aligned limb. Any deviation from this point is considered malalignment. If the line falls toward the medial side of the knee, the limb is in varus alignment; if the line falls toward the lateral side of the knee, the limb is in valgus alignment.

Sagittal plane alignment is determined by measuring the posterior tibial slope. This angle is defined by a line perpendicular to the mid-diaphysis of the tibia and the posterior inclination of the tibial plateau on a lateral radiograph.

Radiographs also identify signs of OA and its severity (e.g., osteophytes, joint space narrowing, subchondral sclerosis, and subchondral cysts), which areas of the knee are affected, limb alignment, posterior tibial slope, patellar height, previous fracture, deformity, and previous surgery as well as previous implants used and the location of the implants.

Magnetic resonance imaging (MRI) is a commonly ordered investigation in patients who present with knee conditions. However, most of the information required for decision-making in patients with knee OA can be gathered from a proper history, physical examination, and the aforementioned radiographs. Bhattacharyya et al. reviewed radiographs and MRI images in 154 patients (men ≥45 years; women ≥50 years) with symptomatic and asymptomatic knee OA. The groups were similar in age. However, patients in the symptomatic OA group had significantly higher body mass index (BMI) scores. The authors found that meniscal tears were highly prevalent in both asymptomatic (76%) and symptomatic (91%) cases of knee OA. Increased radiographic evidence of OA was associated with an increased rate of meniscal tears. No significant difference in pain and function was found on a visual analog scale or the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores between patients with and without a medial or lateral meniscal tear in the osteoarthritic group. Ultimately the etiology of pain in patients with knee OA is multifactorial and can include cartilage lesions, synovial inflammation, and periarticular muscle strains. The investigators concluded that there is no indication for the routine use of MRI in the evaluation and management of patients with OA of the knee.

Treatment Options

Fig. 104.3 shows possible treatment options, from least to most invasive.

Operative Options

Arthroscopy

Arthroscopic lavage, débridement, and/or meniscectomy are not recommended in patients whose primary symptom is pain. In 2002 Moseley et al. conducted the first of two randomized controlled studies of the effect of arthroscopic surgery in patients with OA of the knee who presented with knee pain. They compared arthroscopic surgery with arthroscopic lavage and “sham” surgery in 180 patients and found that results of arthroscopic surgery were no better than those of sham surgery at a follow-up of 2 years. In 2008 Kirkley et al. conducted another randomized controlled trial with 188 patients in which arthroscopic surgery was compared with optimized physiotherapy and medical management. These investigators specifically addressed several weaknesses of the study by Moseley et al., which included the use of a nonvalidated outcome measure and the lack of generalizability of their results. This study also showed no difference among the three groups in WOMAC or Short Form (SF)-36 scores at 2 years after surgery. Dervin et al. studied the ability of two groups of surgeons to independently predict the outcome of arthroscopic débridement based on clinical symptoms, signs, and plain radiography. A total of 126 patients were followed for 2 years subsequent to failure of medical management and arthroscopic débridement. Of these, 56 patients (44%) reported a clinically important reduction in pain on the WOMAC pain scale. Furthermore, the investigators found that physicians correctly predicted outcome only 59% or less of the time.

Arthroscopic surgery is not recommended in patients with documented knee OA. Expert opinion suggests that arthroscopy should be considered only in cases where mechanical symptoms rather than pain are the chief complaint.

Osteotomy

An osteotomy is a bone realignment procedure for unicompartmental arthritis of the knee. The biomechanical principle of osteotomy is to redistribute the weight-bearing forces from the worn to the unworn compartment of the knee to relieve pain and slow disease progression. The most frequently seen deformity is varus alignment due to MCOA, with isolated lateral compartment OA one-eighth as common as isolated MCOA. The majority of osteotomies are performed on the proximal tibia to treat MCOA. Biopsy and second-look arthroscopic and other open procedures have shown that there is regrowth of fibrocartilage in the worn medial compartment with a predilection for the ulcerated regions of wear in the weight-bearing portion of the medial femoral condyle. Box 104.1 outlines the indications for an osteotomy.

Box 104.1

Indications for an Osteotomy

• Malalignment + Arthrosis

• Malalignment + Instability

• Malalignment + Arthrosis + Instability

• Malalignment + Meniscal/Cartilage Transplant ± Instability

Medial compartment osteoarthritis.

Both medial opening wedge high tibial osteotomy (HTO) and lateral closing wedge HTO have been used to successfully treat MCOA ( Fig. 104.4 ). The advantages and disadvantages of each technique are outlined in Table 104.2 .

TABLE 104.2

Medial Opening Wedge Versus Lateral Closing Wedge High Tibial Osteotomy

	Advantages	Disadvantages
Medial opening wedge	The procedure is technically easier to perform (requiring just one bone cut). It provides the ability to achieve a predictable correction in coronal and sagittal planes. It can be combined with other procedures such as ligamentous reconstruction with relative ease. It restores bone stock.	Healing in distraction leads to more potential problems with delayed and nonunion. The tibial slope may be difficult to maintain.
Lateral closing wedge	Healing in compression leads to fewer problems with delayed and nonunion. It provides favorable alterations in the tibial slope to treat chronic anterior cruciate ligament deficiency.	The procedure is technically more difficult for inexperienced surgeons. Peroneal nerve Proximal tibiofibular joint It decreases bone stock. It makes future total knee arthroplasty more technically challenging.

Medial opening wedge high tibial osteotomy.

Historically, along with the points shown in Table 104.2 , the concerns with medial opening wedge HTO have been prolonged immobilization and restricted weight bearing, both of which have a significant impact on the patient's quality of life. Recent improvements in implant technology have led to the development of locking plates for HTO. These devices are much stronger than previous nonlocking implants and allow weight bearing as early as 2 weeks after surgery with no loss of correction of the osteotomy and no delayed union or nonunion. Another concern with medial opening wedge HTO is the morbidity associated with the harvesting of iliac crest bone graft required to fill the osteotomy. However, several recent studies have reported that an autograft, an allograft, and even no graft for corrections of 8 mm or less have produced good results, with union occurring by 12 weeks after surgery.

Lateral closing wedge high tibial osteotomy.

Coventry first described the technique of lateral closing wedge HTO in 1965. Advantages and disadvantages are described in Table 104.2 . Currently our only indication for this procedure is a previous successful lateral closing wedge HTO in the contralateral limb.

Other techniques.

Less commonly used tibial osteotomy techniques include the dome osteotomy and external fixation. These techniques are recommended for deformities greater than 25 degrees as well for those that require gradual rather than acute correction, as in skeletally mature patients with Blount disease or in younger patients with idiopathic genu varum.

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