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  Stiffness after TKA is a common complication. Depending on the definition, it can affect about 1% to 60% of cases, and it is a significant cause for patient dissatisfaction after surgery.

  
  
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  Specific numeric criteria for stiffness after TKA vary, but loose criteria suggest a range of motion (ROM) of 5 to 95 degrees. Stricter criteria describe a ROM of 15 to 75 degrees. It is generally agreed that an arc of motion of less than 70 degrees qualifies as a stiff TKA.

  
  
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  Surgical management consists of revision surgery when malpositioning or malrotation exist. Options are isolated femoral, tibial, or patellar revision and complete revision TKA.

  
  
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  The case study highlights the use of revision options for treatment of knee stiffness after TKA.

Introduction

In the United States, increasing numbers of total knee arthroplasties (TKAs) are being performed, with excellent clinical results. Many investigators have reported survival rates of 90% or better at 10 to 15 years of follow-up. Despite these favorable results, poor outcomes affect a small percentage of patients, some of whom require revision TKA to improve their conditions. As a result, surgeons are seeing an increase in the incidence of revision TKAs.

Among the reasons for poor results is persistent TKA stiffness, with most reports documenting prevalence rates in the range of 1.3% to 12% using strict criteria and up to 60% with the use of an expanded designation of knee stiffness. The definition of stiffness after TKA is a subject of debate, and the number of degrees for an acceptable postoperative range of motion (ROM) remains a moving target. Nicholls and Dorr described stiffness as a ROM of less than 45 degrees and a flexion contracture greater than or equal to 25 degrees. Others have defined stiffness as flexion of less than 70 degrees. It can be argued that the more demanding modern TKA patient sees less than 90 degrees of flexion as a suboptimal result.

The definition of stiffness is likely more complicated than originally described. Biomechanical studies have demonstrated that walking on a level surface requires knee flexion of 65 degrees, arising from a seated position or ascending stairs requires 70 to 85 degrees, descending stairs requires 90 to 100 degrees, and arising from a low chair requires 105 degrees. Flexion contractures in excess of 5 to 8 degrees compromise standard gait patterns. Based on observations that most normal activities of daily living require a threshold of 90 to 100 degrees of knee flexion, many would agree that a ROM of less than 90 degrees comprises stiffness. For these reasons, we define TKA stiffness as flexion of less than 90 degrees and a flexion contracture as greater than or equal to 10 degrees. In the case presentation, the patient demonstrated a significant flexion contracture of 25 degrees and flexion of 80 degrees, satisfying the requirements for the diagnosis of stiffness.

Because stiffness often is a very painful and physically disabling condition, it is a common reason for patient dissatisfaction after TKA. Some authorities even recommend against revision TKA because of previously reported poor results. There is sparse literature on which to base the surgical treatment of knee stiffness after TKA. Elucidating the reasons for stiffness is paramount to optimize treatment strategies. This chapter discusses the causes, evaluation, and treatment of stiffness after TKA, with a focus on the surgical options for revision TKA.

Causes

Stiffness after TKA has many causes, which can be subdivided into patient factors, technical errors, and postoperative complications. Patient factors consist of limited preoperative ROM, effects of previous surgeries, poor motivation regarding rehabilitation protocols, body habitus (e.g., obesity), and biologic predisposition. Limited preoperative knee ROM is the most influential factor on postoperative ROM. The patient in the case study had a history of multiple operations on his knee, including two knee arthroscopies and two TKAs (one primary and one revision).

Intraoperative factors leading to stiffness encompass flexion/extension gap mismatch, joint line elevation (e.g., patella baja), retained posterior osteophytes, anterior tibial slope, inadequate bony resection, incorrect component sizing, component malrotation, and overstuffing of the patellofemoral compartment. Overstuffing of the patellofemoral articulation can be caused by an underresected patella, insertion of an overly thick patellar component, anterior displacement of the anterior flange of the femoral component, or an oversized femoral component. Whatever the reason, overstuffing can ultimately lead to decreased flexion postoperatively because it tightens the soft tissue retinaculum about the knee. Anterior knee pain with motion can lead to a restricted ROM and contractures.

Decreased flexion can also result from a tight flexion gap. A tight flexion gap can be caused by an overly tight posterior cruciate ligament or by underresection of the posterior femoral condyles, which leads to an oversized femoral component. A tight flexion gap can result from a tibial component inserted with anterior tibial slope. Joint line elevation can lead to a situation in which the patella articulates with the polyethylene and tibial tray, limiting the ability to flex the knee.

Decreased extension can result from a tight extension gap in which the amount of distal femur resected was inadequate or a tibial polyethylene liner that was too thick was inserted. Large, retained posterior osteophytes can contribute to decreased extension. Flexion/extension gap imbalance can also alter the joint line, producing an overall patella baja when elevated. Joint line elevation and gap mismatch, a common cause of knee stiffness, must be corrected with revision surgery.

Component malrotation or malalignment can result in arthrofibrosis postoperatively after TKA. Malrotation causes an asymmetric flexion gap, contributing to lift-off and potential patellar tracking problems, both of which can lead to decreased flexion of the knee. Malalignment of components results in an asymmetric extension gap and patellar maltracking, which can cause stiffness. In the case study, the patient had malrotation of the femoral component, which resulted in patellar maltracking and an asymmetric flexion gap.

Postoperative complications that can induce stiffness include sepsis, implant loosening, poor patient motivation, complex regional pain syndrome (CRPS), heterotopic ossification, and arthrofibrosis. Arthrofibrosis comprises excessive and pathologic postoperative scarring, which can compromise flexion and extension. It is often unresponsive to treatment and very difficult to manage. The patient in the case study had three potential sources for residual pain and stiffness: loosening suggested by a bone scan, femoral component internal rotation confirmed on a CT scan, and lateral tilt and maltracking of the patella.

Determining the causes of stiffness preoperatively is crucial for developing a treatment strategy and optimizing outcomes. With regard to performing revision TKA, intrinsic technical factors that can be corrected must be detected to increase the probability of success, because revision TKA undertaken without a clear diagnosis has been fraught with complications and poor results. In our case presentation, the patient did have objective technical factors that were deemed correctible with a surgical plan to include improving component stability, rotational alignment, and patellar tracking.

Evaluation

The workup for a patient with a stiff TKA consists of a thorough history, record review, physical examination, and radiographic analysis. The patient should be asked about and records reviewed for the nature of the preoperative ROM. The type of components should be identified (i.e., cruciate-retaining or cruciate-sacrificing), and actual sizes of components implanted should be ascertained. Radiographs should be scrutinized to assess for potential technical errors such as an oversized femoral component, joint level alteration, an underresected patella, malrotation, or malalignment ( Figs. 16.2 and 16.3 ). Preoperative knee radiographs, if available, can be evaluated for optimal sizing of components. If they are not available, contralateral knee roentgenograms can aid in this respect. Serial radiographs should be assessed, and triple-phase bone scans should be performed as needed to look for evidence of component loosening. Bone scans can also assess the maturity of heterotopic ossification seen on plain radiographs.

Lateral view of a total knee arthroplasty in which the patella was underresected, contributing to a decreased range of motion postoperatively.

Lateral radiograph of a total knee arthroplasty shows a slightly oversized femoral component and a slightly anteriorly translated femoral component, as well as evidence of previous surgery that contributed to postoperative stiffness.

CT scans can be used to diagnose malrotation of the components, which is a common cause of knee stiffness. The workup to rule out infection as a reason for arthrofibrosis consists of a complete blood count with differential, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, and aspiration as needed. Magnetic resonance imaging (MRI) with artifact-sparing protocols is available, but the utility of MRI in determining a cause for postoperative knee stiffness has not been studied.

Indications and Contraindications

Nonoperative treatments for a stiff TKA are discussed in detail in Chapter 14 , Chapter 15 . This chapter focuses on revision options for a stiff TKA.

Before revision surgery, the patient must have ample functional limitations and pain sufficient to merit undertaking the potential risks of an additional operation. The aims of treatment are to address the potential causes of stiffness in a particular patient. Extrinsic sources of knee stiffness must be ruled out, and intrinsic factors must be delineated to increase the chance of success.

After extrinsic causes have been excluded, the ability to correct intrinsic factors is analyzed. Intrinsic or intraoperative factors that can lead to stiffness include overstuffing of the patellofemoral joint, mismatch of the flexion and extension gaps, component malrotation, joint line elevation, retained posterior osteophytes, oversizing or undersizing of components, and a tight posterior cruciate ligament (if retained). Component loosening and prosthetic infection are also surgically correctible causes of knee stiffness. Successful operative intervention is predicated on the ability to adequately correct these issues. Poor surgical results often occur if no conceivable intrinsic factor is identified preoperatively.

Surgery options comprise open arthrolysis with or without modular component exchange (see Chapter 15 ) and revision TKA. Revision TKA should be undertaken if a clear diagnosis for the cause of stiffness can be corrected intraoperatively. In the case study, the workup identified a malrotated femoral component, mild elevation of the joint line, and a possibly loose femoral component. Based on these correctable causes of knee stiffness, revision TKA was offered to the patient.