Knee osteoarthritis (OA) is an extremely common cause of disability. The etiology is multifactorial, but joint injury is an prevalent cause of OA in the knee. Studies have shown that meniscal injury requiring a meniscectomy alters knee biomechanics and leads to gonarthrosis. Anterior cruciate ligament (ACL) rupture, a frequently seen and often devastating injury, is characteristically associated with meniscal and chondral injuries. Further deterioration of the joint related to multiple subluxation episodes over time leads to gonarthrosis that typically affects the medial compartment and results in varus deformity.
History
A thorough history rules 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 103-1 outlines key questions for patients presenting with knee OA.
| Question | Patient Response |
|---|---|
| Identification | Age, occupation |
| Chief complaint | Pain/clicking/locking/swelling/decreased motion/instability |
| History of presenting illness |
|
| Treatments to date | Analgesics, NSAIDs, bracing, physiotherapy, injections, surgery |
| Functional status |
|
| Expectations |
|
Physical Examination
A systematic approach to the physical examination of the knee includes inspection, palpitation, 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 are 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 moving 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 is 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 is not 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 92 ). 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 ( Figure 103-1 ). 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. 103-2 ). 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, and 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 middiaphysis of the tibia and the posterior inclination of the tibial plateau on a lateral radiograph.
Radiographs also identify signs and severity of OA (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 visual analog scale or 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 routine use of MRI for the evaluation and management of patients with OA of the knee.
Treatment Options
Figure 103-3 shows possible treatment options, from least invasive to most invasive.
Nonoperative Treatment Options
Education and Activity Modification
The natural history of OA is a waxing and waning course, with days when symptoms are manageable and days when symptoms seem to worsen. Patients should be educated about self-management techniques, including lifestyle and activity modification. Encouraging patients to take responsibility for their condition allows them to actively participate in their care and has been shown to improve symptoms.
Weight Loss
Patients with symptomatic knee OA who have a BMI score of more than 25 kg/m 2 should be encouraged to lose weight through diet and exercise. Studies have shown an improvement in overall clinical function in the WOMAC function subscale with weight loss. Other studies have shown that weight reduction decreases the knee joint load per step at a ratio of 1 lb lost to a 4-lb reduction in knee-joint load per step. Not only does weight loss have a beneficial effect on symptoms of knee OA, but it also encompasses whole-body health benefits that cannot be overlooked.
Low-Impact Exercise
Multiple studies have shown that low-impact exercise, such as walking, biking, and using an elliptical trainer, have the beneficial effects of decreasing pain and disability in patients with knee OA. The American Geriatrics Society recommends a minimum of 20 to 30 minutes of physical activity per day, two to five times per week, for persons with OA.
Analgesic Medications
Patients who have a symptomatic osteoarthritic knee should be encouraged to use acetaminophen for pain relief. Studies comparing use of acetaminophen (≤4 g/day) with a placebo have shown significant benefit in pain relief without any significant adverse effects.
Nonsteroidal Antiinflammatory Drugs
In patients who have no risk factors for gastrointestinal disease, nonsteroidal antiinflammatory drugs (NSAIDs) may be prescribed for pain relief. Studies have shown a statistically significant, favorable clinical response with the use of NSAIDs versus acetaminophen. Consideration for additional gastroprotective medication along with nonselective NSAID medication or cyclooxygenase-2 inhibitors is recommended. Topical NSAID medication has been shown to improve pain, stiffness, and function and should also be considered.
Braces
The use of an unloader knee brace may be a cost-effective adjunct to treatment and a reasonable option to help decrease symptoms and increase function in patients with knee OA. This type of brace functions by helping to transfer the weight-bearing forces from the worn to the unworn part of the knee. Although it can be used for either varus or valgus deformities, it has been primarily studied in patients with medial compartment OA (MCOA). In a study by Kirkley et al., a varus unloader brace was shown to have significant benefit compared with a neoprene sleeve or medical management alone in decreasing pain and improving function. The authors recommended its use in patients with symptomatic unicompartmental OA who have a correctable deformity and an average-sized leg. Also, the use of an unloader brace may help determine if the patient will have any benefit from a limb realignment procedure. A further advantage of bracing relates to proprioception. Studies have shown that patients with knee OA have decreased proprioception. Kirkley et al. report that knee braces offer a proprioceptive benefit. The disadvantages to bracing are compliance, difficulty in obtaining a proper fit, and cost.
Physical Therapy
Quadriceps-strengthening exercises have been shown to provide a significant benefit for symptomatic pain relief. The use of ROM and stretching exercises has not been studied extensively, and their clinical effect is unknown. However, flexibility and motion exercises appear to have no adverse effects and offer many health benefits.
Injections
Intraarticular corticosteroid injections may be prescribed for short-term relief of acute pain due to an arthritic “flare-up.” Studies have shown that the mean duration of the effect of a corticosteroid injection is 1 week. On the other hand, the benefit of viscosupplementation with hyaluronic acid injections has not been completely established. High-quality studies are scarce, and previous studies have had problems with bias and unclear significance of the selected outcomes. Although a clear recommendation cannot be made for viscosupplementation, in general it seems to provide a positive trend in clinical effect with minimal adverse effects and therefore may be used in selected patients.
Treatment Not Recommended
Several treatment options such as glucosamine and/or chondroitin, lateral heel wedges, and needle lavage have historically been prescribed as nonoperative treatment options for patients with symptomatic OA of the knee. However, a sufficient number of high-quality studies have shown that glucosamine hydrochloride and/or chondroitin sulphate have no clinical benefit compared with placebo. Likewise, no good evidence exists to support the prescription of lateral heel wedges for MCOA of the knee. Lastly, studies recommending needle lavage have been of poor quality, and the procedure has not been shown to have any lasting benefit.
Operative Options
Arthroscopy
Arthroscopic lavage, debridement, 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 debridement based on clinical symptoms, signs, and plain radiography. One hundred twenty-six patients were followed up for 2 years subsequent to failure of medical management and arthroscopic debridement. Fifty-six patients (44%) reported a clinically important reduction in pain on the WOMAC pain scale. Furthermore, they 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 in which mechanical symptoms rather than pain are the chief complaint.
Osteotomy
An osteotomy is a bony 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 103-1 outlines the 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. 103-4 ). The advantages and disadvantages of each technique are outlined in Table 103-2 .
| Advantages | Disadvantages | |
|---|---|---|
| Medial opening wedge |
|
|
| Lateral closing wedge |
|
|
Medial Opening Wedge HTO.
Historically, along with the points shown in Table 103-2 , 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 HTO.
Coventry first described the technique of lateral closing wedge HTO in 1965. Advantages and disadvantages are described in Table 103-2 . 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.
Lateral Compartment OA
Lateral compartment OA can be caused by pathology on the femoral or tibial side of the knee. The osteotomy should be performed at the site of the cause of the deformity.
Proximal Tibial Osteotomies.
The results of proximal tibial varus osteotomies have not equaled those of proximal tibial valgus osteotomies. A concern remains that proximal tibial osteotomies for lateral compartment OA will cause joint line obliquity greater than 10 degrees, leading to lateral subluxation of the tibia. Another concern is that medial collateral ligament (MCL) laxity occurs if the wedge is taken above the MCL insertion. However, a role still exists for proximal tibial osteotomy in the valgus knee. This role includes small corrections of 12 degrees or less that avoid excessive joint line obliquity in persons with posttraumatic OA for whom the deformity is primarily at or below the joint. If the deformity is primarily in the femur or the correction is greater than 12 degrees, a distal femoral osteotomy should be considered.
Distal Femoral Osteotomies.
A distal femoral varus osteotomy is an appropriate procedure for patients with valgus deformity of the femur, such as a hypoplastic lateral femoral condyle, or if the required correction is greater than 12 degrees. Again, this procedure can be a medial closing wedge or a lateral opening wedge osteotomy. The advantages and disadvantages of each procedure are similar to those listed for opening and closing wedge proximal tibial osteotomies in persons with MCOA (see Table 103-2 ). One additional advantage of a lateral opening wedge distal femoral osteotomy is that the correction can be tailored to the desired amount of varus. On the other hand, the medial closing wedge technique using a 90-degree blade plate typically results in a tibiofemoral angle correction of 0 degrees and a mechanical axis correction of 6 degrees varus. Whether tailoring the correction with a lateral opening wedge technique is superior to using the medial closing wedge technique with regard to long-term outcome has yet to be determined.
Knee Instability
Knee instability can be due to both bony and soft tissue factors. Ligamentous causes are the most common. However, altered tibial slope in the sagittal plane occurring in isolation as a result of a tibial physeal arrest or in combination with ligamentous insufficiency can also cause anterior-posterior instability. In such cases, the condition must be corrected to create a stable joint before ligamentous reconstruction, and a combined ligamentous and bony procedure should be considered to decrease the risk of graft failure. Normally the posterior tibial slope is 10 degrees ± 3 degrees. A posterior tibial slope greater than 13 degrees results in anterior tibial translation and altered joint biomechanics, as well as meniscal load sharing, leading to increased chondral wear. Similarly, a posterior tibial slope of less than 7 degrees (relative decreased slope) is also considered abnormal and leads to posterior translation of the tibia and may have a similar outcome. When these conditions are symptomatic, they should be addressed with an osteotomy to improve the bony stability. Osteotomies for sagittal plane deformities are usually approached anteriorly with either an anterior closing wedge osteotomy for increased tibial slope or an opening wedge osteotomy for decreased slope.
Combined Instability and Pain
Patients with chronic ligament deficiency may present with pain, instability, or both characteristics. Patients most commonly have chronic ACL deficiency. However, posterior cruciate ligament and posterolateral corner insufficiency may also be present. It has been shown that in patients with instability and malalignment, soft tissue ligamentous reconstruction is at risk of failure because of the malalignment. Therefore an osteotomy to correct the malalignment followed by simultaneous or staged ligamentous reconstruction should be considered.
In patients whose primary symptom is instability with mild or moderate medial compartment degeneration, an osteotomy alone may not prove beneficial. Although ligament reconstruction alone has been shown to be successful, it does not address the malalignment, predictably alleviate any symptoms of pain, or offer any chondroprotection to the damaged medial compartment. In these patients, an osteotomy to address pain combined with a simultaneous or staged soft tissue procedure to address ligament deficiency should be considered.
In patients presenting with chronic ACL deficiency, treatment options include lateral closing wedge osteotomy or combined HTO and ACL reconstruction. A lateral closing wedge osteotomy favorably decreases the tibial slope, which helps improve instability related to ACL deficiency. A medial opening wedge osteotomy tends to change tibial slope in an unfavorable direction, and therefore combined procedures should be considered. Previous studies have described combined HTO and ACL reconstruction as simultaneous or staged procedures, with the osteotomy usually performed first. Simultaneous medial opening wedge HTO and ACL reconstruction allows for biplanar correction of the knee deformity with restoration of ligamentous support in one operation and results in improvements in both bony and soft tissue support, which in theory leads to improved overall knee joint function.
Return to Sport After an Osteotomy
The true benefit of an osteotomy is that is allows unrestricted activity while preserving the knee joint. Multiple studies have shown that HTO affords young, active patients with OA the ability to return to recreational sports and to maintain an active lifestyle. Van Raaij et al. found that HTO postpones primary total knee arthroplasty (TKA) for a median of 7 years in this group of patients.
Patient Satisfaction After HTO
With careful patient selection, satisfaction after HTO is very high. Hui et al. showed that at a mean follow-up of 12 years, 85% of a cohort of 397 patients who underwent lateral closing wedge HTO were enthusiastic or satisfied and 84% would have the same surgery again. Similarly, at a mean of 6.5 years after surgery, Tang and Henderson reported patient satisfaction of 76%, with 90% of patients saying they would choose the same surgery again.
Arthroplasty
Medial Compartment Osteoarthritis
For many years, unicompartmental knee arthroplasty (UKA) has been performed to treat isolated MCOA. The potential benefits of UKA compared with TKA are lower perioperative morbidity, less blood loss, maintenance of normal knee kinematics, and quicker patient rehabilitation and recovery. Controversies remain regarding a fixed bearing versus mobile bearing implant design, but both have shown good long-term success. However, concern remains regarding the durability of UKA in younger patients.
Tricompartmental Osteoarthritis
In patients presenting with severe tricompartmental osteoarthritis, the gold standard is a TKA. This procedure offers long-term, predictable pain relief. TKA for symptoms other than pain, such as stiffness, swelling, or instability, has unpredictable outcomes and is not recommended.
Combined Instability and Pain
Historically, ACL insufficiency has been a contraindication to UKA because of concerns relating to increased anterior tibial translation and altered knee biomechanics with subsequent increased lateral compartment arthrosis and polyethylene wear resulting from posterior loading of the implant and ultimate prosthesis failure. Recently, combined UKA using the Oxford prosthesis (Biomet, Oxford, UK) and ACL reconstruction has been performed to address both instability and pain related to MCOA. However, controversy remains regarding implant survival in this subgroup. Lateral UKA is contraindicated in patients with ACL insufficiency because of increased lateral compared with medial compartment mobility, which leads to even more abnormal contact pressures and a potentially higher rate of failure.
Return to Sport After Arthroplasty
Parratte et al. reviewed data for 31 patients who underwent UKA at a mean age of 46 years (range, 41 to 49 years) and who were allowed unrestricted activity after surgery (data for a total of 35 knees were reviewed). At a mean follow-up of 9.7 years (range, 5 to 16 years), 75% had returned to manual work at the same level as before surgery, 60% had returned to the same level of participation in sports, and 30% were participating in sports at a lower level. Ten percent were unable to return to their sport. The authors acknowledge that revision for polyethylene wear remains the main concern. In a biomechanical study, Kuster previously demonstrated that running and jumping produces surface loads that exceed the limits of polyethylene resistance. The general recommendation for return to sport after an arthroplasty is low-impact activities such as cycling, bowling, swimming, scuba, golf, skating, cross-country skiing, weight lifting, dancing, and walking.
Decision-Making Principles
Management of patients with knee OA should be individualized. Physiologic rather than chronologic age should be considered, along with the patient’s goals and expectations. Patient education is paramount to successful management of these patients. Figure 103-5 outlines the treatment algorithm for patients presenting with knee OA. Management always begins with nonoperative treatment and progresses from less invasive to more invasive options ( Fig. 103-3 ).
Medial Compartment Osteoarthritis
Several factors need to be considered when deciding the best surgical treatment for patients with isolated MCOA of the knee for whom conservative management has failed. Table 103-3 outlines the indications for HTO versus UKA versus TKA in these patients.
| HTO | UKA | TKR | |
|---|---|---|---|
| Age * | ≤65 yr | ≥55 yr | ≥65 yr |
| Activity level | High | Low | Low |
| Body mass index | Any | <30 | <30 |
| Malalignment | 5°-20° | 0°-5° | Any |
| AP instability | Any | None † | Any ‡ |
| ML instability | ≤Grade II | None | Any ‡ |
| ROM | Arc ≥120° | Arc ≥90° | Any |
| MCOA | Any | Any | Any |
| PFOA | ≤Grade II § | ≤Grade II § | Any |
| LCOA | Any | Any | Any |
* Physiologic age should be considered here.
† Long-term results of combined anterior cruciate ligament reconstruction and UKA have not been established.
‡ Increasing instability requires increased component constraint.
§ For MCOA, the patient may have up to grade II PFOA if no patellofemoral symptoms are present.
Lateral Compartment Osteoarthritis
In general, lateral compartment OA is better tolerated than MCOA. The treatment algorithm for patients with symptomatic lateral compartment OA of the knee for whom conservative management has failed is shown in Figure 103-6 . The lateral compartment UKA procedure remains controversial and is not recommended until longer term results are reported.
Chronic ACL Insufficiency
Figure 103-7 outlines the treatment algorithm for patients who present with symptomatic instability and pain caused by chronic ACL insufficiency. Use of UKA in patients with chronic ACL insufficiency with or without combined ACL reconstruction is controversial and is not recommended.
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