You are in: eMedicine Specialties > Orthopedic Surgery > KNEE Lateral Compartment ArthritisArticle Last Updated: Jan 19, 2007AUTHOR AND EDITOR INFORMATIONAuthor: B Sonny Bal, MD, Associate Professor, Department of Orthopedic Surgery, University of Missouri School of Medicine B Sonny Bal is a member of the following medical societies: American Academy of Orthopaedic Surgeons Coauthor(s): Ashish Upadhyay, MD, MBMS, MRCS (Edinburgh), Research Fellow, Department of Orthopedics, University of Missouri at Columbia Editors: Dennis P Grogan, MD, Clinical Professor, Department of Orthopedic Surgery, University of South Florida College of Medicine; Chief of Staff, Department of Orthopedic Surgery, Shriners Hospital for Children of Tampa; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Thomas M DeBerardino, MD, Director, John A Feagin, Jr Sports Medicine Fellowship at West Point, Clinical Instructor in Surgery, Orthopedic Surgery Service, Keller Army Community Hospital at West Point; Dinesh Patel, MD, FACS, Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital; Carlos J Lavernia, MD, FAAOS, Adjunct Clinical Professor, Department of Orthopedic Surgery, University of Miami School of Medicine; Medical Director, Orthopedic Institute at Mercy Hospital Author and Editor Disclosure Synonyms and related keywords: degenerative joint disease, knee arthrosis, gonarthrosis, genu valgum INTRODUCTIONDegenerative joint disease can affect any or all of the compartments of the knee joint. This article addresses arthrosis that is localized to the lateral compartment of the knee. The typical radiographic signs that are associated with degenerative joint disease consist of narrowing of the joint space, subchondral cyst formation, bone sclerosis, and hypertrophic osteophytic spurring (Altman et al, 1987; Gresham and Rathey, 1975). Lateral compartment arthrosis is encountered less frequently than a genu varum deformity because the medial joint compartment of the knee is most commonly affected by degenerative changes, followed by the patellofemoral and lateral compartments (Johnson and Bodell, 1981). ProblemDuring normal gait, adduction places forces predominantly on the medial compartment (Andriacchi, 1994; Goh et al, 1993; Harrington, 1983; Johnson et al, 1980; Maquet, 1976; Prodromos et al, 1985; Wada et al, 1998). As a result, a valgus deformity is necessary to shift the weight-bearing stresses to the lateral tibial plateau of the knee (Shaw and Moulton, 1996). The anatomic axis of the lower extremity is defined by the femorotibial angle, which averages 5° of valgus (Kettelkamp et al, 1976); the mechanical axis of the lower extremity is defined by a plumb line connecting the center of the femoral head to the mid ankle on a standing anteroposterior (AP) weight-bearing radiograph. The mechanical axis averages 1.2° of varus (Hsu et al, 1990), and it is more accurate than the anatomic axis in demonstrating load transmission across the knee joint, especially if femoral or tibial deformities contribute to limb malalignment (Hsu et al). EtiologyUsually, a genu valgum deformity is the result of a dysplastic lateral femoral condyle that contributes to pathologic loading of the lateral compartment of the knee and subsequent bone and cartilage destruction (Washington, 1995). In such cases, genu valgum results from a valgus orientation of the distal part of the femur relative to its long axis (Cooke et al, 1994; Poilvache et al, 1996; Yoshioka et al, 1987). An experimental model (Goodman et al, 1991) has demonstrated that the mechanical overloading of a single compartment of the knee leads to degenerative change in that compartment. The etiology of lateral compartment arthritis can also include degenerative changes caused by trauma, such as a lateral tibial plateau fracture. A discoid lateral meniscus reportedly is present in 1.4-15.5% of the population, with a wide variation in its prevalence among various races (Casscells, 1978; Dickhaut and DeLee, 1982; Ikeuchi, 1982). Complete arthroscopic resection of a discoid meniscus in children can lead to the subsequent development of degenerative changes in the lateral compartment (Aglietti et al, 1999; Washington et al, 1995). Removal of the lateral meniscus has been shown to lead to the development of lateral compartment arthritis in an animal model (Little et al, 1997). Spontaneous osteonecrosis of the femoral condyle is a clinical entity that typically occurs in women older than 55 years, and it presents with the acute onset of pain (Ecker and Lotke, 1994; Lotke and Ecker, 1988; Lotke and Ecker, 1985). Lateral compartment degenerative disease may be the ultimate complication of spontaneous osteonecrosis of the lateral femoral condyle. PathophysiologyArthritic destruction of the lateral compartment of the knee manifests as a genu valgum deformity. A valgus deformity is defined as a malalignment that exceeds the normal 7-10° femorotibial valgus angulation (Washington et al, 1995; Miyasaka et al, 1997; Whiteside, 1993). Early in the disease process, a weight-bearing radiograph in the posteroanterior (PA) projection with the knee flexed at 45° can demonstrate lateral joint-space narrowing from erosion of the posterior femoral condyle that may not be apparent on the routine AP films (Dervin et al, 2001). With advanced disease, cartilage and bone erosion that lead to joint-space narrowing in the lateral compartment is observed on the weight-bearing AP radiographs as well. With progressive valgus malalignment, the medial soft tissues of the knee joint stretch, whereas the lateral soft-tissue structures of the knee, including the lateral collateral ligament, iliotibial band, and lateral capsule, contract. Over time, these deformities become fixed (see Image 1). ClinicalPatients with lateral compartment arthritis of the knee joint typically have pain and grinding that are localized to the lateral aspect of the knee. Patellofemoral symptoms may or may not be present, depending on the degree of degenerative change at this articulation. With advanced disease and deformity, patients notice a valgus orientation of the knee joint. Abnormal gait patterns may manifest as a limp, back pain, and foot pain. The history may reveal contributing factors to lateral compartment gonarthrosis, such as previous trauma to the knee or a lateral meniscectomy. Reproduction of symptoms is possible during physical examination by applying a valgus stress to the knee joint and taking the knee through a range of motion. Crepitation can usually be palpated along the lateral joint line during movement and may be associated with swelling and laxity of the joint, which can be detected by application of a varus stress (Shakespeare, 2006). Careful palpation of the patellofemoral joint can be used to isolate tenderness at this location. If arthritis is localized to the lateral compartment, the knee should have a smooth arc of motion when a varus stress is applied to it. Examination of the other joints in the lower extremities (ie, hips, ankles, contralateral knee) and assessment of the neurovascular status of the limb contribute information that is useful in making the diagnosis of lateral compartment arthritis of the knee joint and formulating treatment options. INDICATIONSThe surgical interventions that are available to treat lateral compartment degenerative disease of the knee are corrective osteotomy, hemiarthroplasty of the knee, and total knee replacement (TKR). For indications for each specific surgical procedure, see Treatment, Surgical therapy. RELEVANT ANATOMYThe anatomy that may be encountered in surgery for lateral compartment arthritis of the knee depends on the etiology of the degenerative changes. For example, with a history of a lateral tibial plateau fracture, deformity and deficiency of the lateral tibia can be expected. A unicompartmental knee or total knee arthroplasty (TKA) in such a knee joint may require augmentation of the deficient plateau with allograft or build-up of the prosthesis. During TKR, a hypoplastic femoral condyle may require augmentation with metal blocks on the femoral prosthesis. Contracted lateral soft tissues mandate sequential release during arthroplasty and may preclude corrective osteotomy. Abnormal patella biomechanics may be manifested by lateral patella tracking and degenerative changes along the lateral facet of the patella from a long-standing valgus deformity of the knee. Knowledge of the etiology that led to lateral arthritis of the knee, careful physical examination, and evaluation of imaging studies will alert the surgeon to the anatomic changes that can be expected during surgery. CONTRAINDICATIONSContraindications to the surgical procedures used to treat lateral compartment arthritis are discussed in Treatment, Surgical therapy. WORKUPLab Studies
Imaging Studies
Diagnostic Procedures
TREATMENTMedical therapyValgus deformities of the knee are better tolerated than varus deformities and develop arthritic changes later (Langlais and Thomazeau, 1989; Maquet et al, 1967). Because lateral compartmental arthrosis usually develops later in life than medial compartment arthrosis, it is often better tolerated and has a lower incidence rate (Ahlback, 1968; Hernborg and Nilsson, 1977). As a result, nonoperative treatment may suffice to control symptoms early in the course of the disease, despite the absence of controlled studies to verify the efficacy of nonoperative treatment of lateral compartment arthritis. Nonsurgical palliative modalities include weight loss, shoe modification, oral analgesics, quadriceps exercises, unloader bracing, activity modification, and the use of a cane during ambulation (Ogata et al, 1997). Nonoperative treatment is of value in a limited number of patients who have valgus knees with lateral compartment arthritis. When the deformity is mild, treatment with analgesics, aerobic conditioning of the lower extremity muscles, activity modification, and weight reduction may alleviate symptoms. Initial nonoperative treatment can give the physician time to educate the patient about the disease, to understand the patient's needs, and to evaluate the patient's compliance with a treatment program. The knowledge gained can be valuable in planning surgical interventions. The use of an unloader brace in the flexible genu valgum deformity can be helpful in temporizing the situation until definitive surgical treatment. Pain relief with bracing may indicate that a corrective osteotomy or unicompartmental knee replacement would be effective. Surgical therapyThe surgical interventions available to treat lateral compartment degenerative disease of the knee are corrective osteotomy, hemiarthroplasty of the knee, and TKR. Osteotomy The theory behind corrective osteotomy is to unload the diseased lateral compartment by overcorrecting the pathologic malalignment of the lower extremity and to facilitate the reparative capacity of the knee joint once it is mechanically unloaded (Aglietti and Menchetti, 2000; Coventry, 1987; Coventry, 1973; Coventry and Bowman, 1982; Insall, 1993; Ivarsson et al, 1990; Majima et al, 2000; Stuart et al, 1990). The regeneration of articular cartilage and fibrocartilage proliferation has been demonstrated during repeat arthroscopy, compared with previous arthroscopic findings in knees that were overcorrected by an osteotomy (Odenbring et al, 1992). General selection criteria for osteotomy for genu valgum include age younger than 65 years, isolated Ahlback grade I or II lateral compartmental arthrosis (Ahlback, 1968), minimum ligamentous laxity, >90° arc of motion of the knee, and a flexion contracture of <15-20° (Hanssen et al, 2001). Knee extension loss >15° and flexion <90° are contraindications to a distal femoral corrective osteotomy (McDermott et al, 1988; Morrey and Edgerton, 1992). Severe ligamentous instability is another contraindication to osteotomy because there are no dynamic restraints to medial laxity, which will persist even if the alignment is correct (Insall). Poor results with femoral osteotomy have been reported in the presence of preoperative recurvatum of the knee, which may indicate that the knee is at an advanced stage in the arthritic evolution, with TKR being the appropriate option (Hernigou et al, 1992). A specific pattern of posterolateral arthritis has been described in young patients with a history of trauma and a previous lateral meniscectomy. Bone-on-bone contact can be observed in such cases with a PA flexion weight-bearing view but is not observed with standing radiographs in extension weight bearing, reflecting a rotatory problem that may not respond well to valgus osteotomy (Stubbs, 1995). A valgus malalignment of almost any magnitude in the knee joint is best corrected by a distal femoral osteotomy, with a medial closing wedge fixed internally (Cameron et al, 1997; Edgerton et al, 1993; Healy et al, 1988; Mathews et al, 1998; McDermott et al; Miniaci et al, 1990). Images 1-2 illustrate a knee treated with a medial wedge closing osteotomy. An opening wedge osteotomy of the distal femur with the apex of the wedge at the medial femoral cortex, supported by a tricortical autograft wedge and lateral plate fixation, also has been described (Terry and Cimino, 1992). To bring the knee joint line parallel to the floor by osteotomy, the deformity usually has to be corrected in the deformed distal femur itself (Cooke et al; Healy and Wilk, 1994; Insall; Shoji and Insall, 1973). Rarely, a laterally sloping tibial plateau may result in a valgus deformity in some knees (Johnson et al). In such cases, provided that the deformity is mild and the correction is <10°, a varus-producing tibial osteotomy can be successful (Bauer et al, 1969: Coventry, 1987; Marti, 2001). However, if major correction of a valgus deformity is attempted by a tibial osteotomy, the joint line obliquity is exaggerated by bone wedge removal, because most valgus knees have inherent superolateral obliquity of the joint line (Bauer et al; Cameron et al; Coventry, 1987; Coventry, 1973; Coventry and Bowman; Healy et al, 1988; McDermott et al; Shoji and Insall). Clinical failure occurs in such cases because of medial subluxation of the femur along the tilted joint line (Harding, 1976; Insall; Shoji and Insall). Arthroscopy of the knee joint is indicated in the valgus knee if mechanical symptoms are suggestive of intra-articular pathology, such as an incarcerated lateral meniscus. However, knee arthroscopy performed routinely during corrective osteotomy for genu valgum is of questionable clinical value. Clinical outcomes of osteotomy patients with simultaneous arthroscopic debridement of the lateral compartment are not different from the outcomes of those patients who underwent osteotomy alone (Akizuki et al, 1997). Furthermore, the prognostic value of knee arthroscopy has not been demonstrated when the knee joint is visualized to evaluate the extent of degenerative disease before corrective osteotomy. Patellofemoral arthritis may be present in knees with an angular deformity (Elahi et al, 2000), and the specific observation of moderate or severe patellofemoral arthritis has not been demonstrated to affect the clinical results following corrective osteotomy of the knee (Keene et al, 1989; Odenbring et al). The reported results of corrective osteotomy of the distal femur for genu valgum are variable, reflecting uncontrolled factors such as patient selection, surgical techniques, postoperative alignment, and follow-up time (Aglietti and Menchetti; Beaver et al, 1991; Cameron et al; Conrad et al, 1985; Cooke et al; Edgerton et al; Healy et al, 1988; Johnson and Bodell; Mathews et al; McDermott et al; Miniaci et al; Terry and Cimino). Of these factors, the influence of postoperative alignment of the extremity upon the clinical outcome is well documented. In a report of knees corrected to neutral or varus (Edgerton et al), the success rate was 77% compared with a 60% success rate in those knees that had some residual valgus. Although no prospective clinical trials are available to guide the exact postoperative alignment following distal femoral osteotomy, a neutral alignment of the leg with the tibiofemoral angle of 0° is generally accepted as the desired postoperative correction (McDermott et al). The reasoning is that in the valgus knee that has been corrected to neutral, most of the weight-bearing load is transmitted through the medial compartment (Andriacchi; Maquet, 1980; Maquet, 1976; Shaw and Moulton); therefore, no need exists to overcorrect into varus. In addition to the usual risks expected of a major reconstructive procedure, 2 complications have a higher incidence following supracondylar femoral osteotomy than in proximal tibial valgus-producing osteotomy. First, joint stiffness is more frequent following a supracondylar osteotomy compared with proximal tibial valgus-producing osteotomy (Beaver et al, 1991; Cass and Bryan, 1988; Edgerton et al; Johnson and Bodell; Mathews et al), and it can complicate surgical exposure during subsequent TKR (Beyer et al, 1994). Avoiding entry into the knee joint may reduce the rate of this complication (Aglietti et al, 1987). Second, supracondylar osteotomy of the femur is associated with a higher risk of nonunion than is proximal tibial osteotomy. Reported risks of nonunion following an osteotomy of the distal femur range from 4.2-19% (Beaver et al; Edgerton et al; Healy et al, 1998; Mathews et al; McDermott et al; Miniaci et al; Stahelin et al, 2000). Nonunion and hardware failure can be associated with medial placement of the fixation plate (Miniaci et al). The treatment of delayed union or nonunion consists of bone grafting of the delayed union or nonunion site with application of a lateral T-plate (Cameron, 1992). TKR If stringent patient selection criteria are used, few patients qualify for a corrective osteotomy to treat a genu valgum deformity. Because lateral compartment arthritis occurs later in life and because the deformity is generally well tolerated, most patients qualify for a TKR instead (Berruto et al, 1993). The classification proposed by Krackow et al (1991) can serve as a guide to the deformities that are encountered while performing a TKR in the valgus knee. Valgus deformities of the knee have been classified by Krackow into the following 3 distinct types:
Because of the contracted lateral soft tissues, ligamentous balancing during TKA in the valgus knee may require extensive releases on the lateral side of the joint. Correction of valgus deformity in TKA has been associated with an increased risk of patellofemoral instability and peroneal palsy. The incidence of posterolateral instability has been reported to be as high as 4% in such knees (Laurencin et al, 1992). The incidence of peroneal palsy after routine TKR has been estimated as less than 1%, with the incidence in valgus knees reported at 3-4% (Krackow et al, 1991; Washington et al). A technique of graduated intra-articular release of the posterolateral capsule and the iliotibial band and preserving the popliteus may reduce the risk of posterolateral instability and peroneal palsy following TKA in the valgus knee (Miyasaka et al). The correction of severe angular deformities may require both the release of soft tissue on the lateral side and ligament tightening on the medial side (Healy, 1998; Krackow, 1990). Severe bone loss and dysplasia of the lateral femoral condyle may necessitate the use of bone grafts or metal blocks to augment the femoral component. A reasonable option in the patient who is elderly with a severe valgus deformity may be the use of primary constrained implants. Images 3-4 illustrate a severe valgus deformity treated with a primary constrained TKR. Three clinical series have reported that conversion of a supracondylar femoral osteotomy of the knee to a TKA does not compromise the ultimate result of arthroplasty (Beyer et al; Cameron and Park, 1997; Finkelstein et al, 1996). Some authors have found conversion of a previous varus osteotomy to TKA more technically demanding (Finkelstein et al), whereas others report increased difficulty when total joint arthroplasty is performed after supracondylar varus osteotomy (Beyer et al). Unicompartmental knee replacement In selected patients, a unicompartmental knee arthroplasty may be the optimal option for pain relief from isolated lateral compartment arthritis (Cartier et al, 1996; Marmor, 1984; Ohdera et al, 2001; Scott and Santore, 1981; Squire et al, 1999). Images 5-6 illustrate the treatment of lateral compartment arthritis with a unicompartmental knee replacement; compared with osteotomy, unicompartmental knee replacement has a higher initial success rate and fewer early complications (Scott and Santore). In addition, when compared with a tricompartmental knee replacement, unicompartmental replacement preserves both cruciate ligaments and, therefore, almost-normal knee kinematics (Cartier et al; Scott and Santore; Walton et al, 2006); the surgery can be performed through a smaller incision, with reduced blood loss, expense, and morbidity. Bone stock is preserved in the opposite compartment and in the patellofemoral joint, making revision surgeryeasier to perform—at least in theory. Contraindications to unicompartmental arthroplasty include eburnated bone at the patellofemoral compartment or in the opposite compartment, subluxation of the femur on the tibia, fixed lateral contractures, and a significant inflammatory component to the arthritis (Cartier et al; Marmor; Scott and Santore; Squire et al). In these situations, a TKR is the preferred option. Author's preferred treatment If the patient complains of predominantly mechanical symptoms, such as painful catching in the lateral part of the knee joint, and if evidence exists of intra-articular pathology, such as a torn lateral meniscus that is depicted on an MRI, arthroscopy of the knee is undertaken. Removal of the torn portion of the meniscus can relieve preoperative symptoms and allow assessment of the degree of arthritic change in the lateral compartment of the knee and elsewhere. The integrity of the cruciate ligaments and the degree of inflammatory changes in the knee can be evaluated during arthroscopy, and this information is of value in planning future surgical treatment. A distal femoral osteotomy is the author's preferred option for the young, active, and heavy individual, with the goal of correcting the alignment to neutral. An opening wedge osteotomy is preferred, because this can be performed with a smaller incision, and the hardware can be placed on the biomechanically favorable lateral aspect of the femur. The operation is performed through a midline incision to facilitate later TKR. In the older patient who presents with isolated lateral compartment symptoms and radiographic-evident disease, a unicompartmental knee arthroplasty is preferred. Preoperative selection criteria for a unicompartmental arthroplasty include an AP radiograph of the knee joint with a varus stress applied to the extremity. If this radiograph demonstrates normal alignment of the extremity and opening of the arthritic lateral joint space, a lateral unicompartmental knee arthroplasty is performed. For patients who have diffuse symptoms in the knee, a history of inflammatory arthritis, obesity, fixed lateral contractures, and evidence of degenerative disease in the medial or patellofemoral compartments of the knee, a TKR will provide more predictable results. Follow-upFor excellent patient education resources, visit eMedicine's Foot, Ankle, Knee, and Hip Center and Arthritis Center. Also, see eMedicine's patient education articles Knee Pain and Knee Joint Replacement. COMPLICATIONSFor complications related to specific surgical procedures, see Treatment, Surgical therapy. OUTCOME AND PROGNOSISResults with various surgical procedures are discussed in Treatment, Surgical therapy. FUTURE AND CONTROVERSIESAlthough medial unicompartmental knee arthroplasty has become a well-accepted procedure (Price et al, 2005; Pandit et al, 2006; Soohoo et al, 2006), the outcome of minimally invasive unicompartmental knee arthroplasty in the treatment of isolated lateral compartment arthritis of the knee will need to be evaluated with follow-up studies in the future. Similarly, outcome studies are needed to evaluate the results of opening wedge osteotomies of the distal femur to correct a valgus deformity of the knee. Whereas a corrective opening wedge osteotomy has certain advantages over a closing wedge osteotomy, follow-up studies are necessary to ensure that the outcomes are similar to those already reported in the literature. MULTIMEDIA
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Lateral Compartment Arthritis excerpt Article Last Updated: Jan 19, 2007 | ||||||||||||||||||||||||||||||||||||||||||