What Causes a Stiff Knee after TKA – and How Can It Be Prevented?

    Dr. Jesse Otero answers ICJR’s questions about the most common causes of knee stiffness after total knee arthroplasty, what to do if a patient presents with stiffness, and when to consider a revision procedure.

    ICJR: What is the definition of a “stiff knee” after total knee arthroplasty (TKA)?

    Jesse E. Otero, MD, PhD: The goals of TKA are to relieve pain and restore function in patients with moderate to advanced osteoarthritis who have exhausted conservative treatments but still have knee pain that interferes with their activities of daily living. In most patients’ minds, the ideal result of TKA would be a knee that moves and feels the way it did in a more youthful time.

    Before discussing stiffness after TKA, it is essential to first review normal native knee motion in relation to the activities patients routinely perform. Laubenthal et al [1] presented a quantitative analysis of knee motion required to achieve normal activities of daily living. In this classic article, the authors used an electro-goniometer to show that on average:

    • 83° of flexion is required for climbing stairs
    • 93° of flexion is required for sitting
    • 106° of flexion is required for tying a shoe
    • 117° of flexion is required for squatting to lift an object

    The widely accepted target after TKA, based on this study, is 120° of knee flexion. In objective terms, therefore, knees that fail to achieve 120° of flexion after surgery are commonly considered to be stiff.

    However, It is important to remember that subjectivity plays a major role in a patient’s interpretation of their TKA result. For example, a patient who undergoes TKA and achieves 120° of flexion may feel that the knee is stiff if the contralateral knee has a higher degree of flexion. Conversely, a low-demand, older adult patient might be satisfied with 90° of flexion if motion is pain-free and flexion was limited preoperatively.

    ICJR: What are the most common causes of knee stiffness?

    Dr. Otero: A number of preoperative, intraoperative, and postoperative factors can cause stiffness after TKA, as outlined below.

    Preoperative Factors

    Preoperative knee stiffness. Patients with restricted range of motion prior to TKA tend to have restricted range of motion postoperatively. [2] A patient with profound limitation of motion will likely have worse motion postoperatively than a patient with a lesser degree of stiffness preoperatively. Potential etiologies include the following:

    • Postoperatively, the patient continues to engage in lifestyle habits that had caused preoperative stiffness.
    • Intraoperatively, the surgeon failed to – or could not – address anatomic changes that support stiffness, such as capsule, muscle, and tendon contractures.

    Indication for surgery. Total knee arthroplasty is indicated to improve knee pain and promote function in a variety of conditions. Certain preoperative indications portend a worse prognosis in terms of knee motion postoperatively.

    • Post-traumatic osteoarthritis. In one study, total knee patients who previously underwent open reduction and internal fixation of a tibial plateau fracture had a post-operative arc of motion of 105°. [3]
    • Failed unicompartmental knee arthroplasty (UKA). Several studies have documented a higher complication rate and reduced postoperative patient satisfaction after conversion of a UKA to a TKA. [4,5] A recent meta-analysis also summarized postoperative motion results after conversion of a UKA to a TKA. [6] Across the board, a failed UKA conversion to TKA results in poorer motion compared with a primary TKA.

    Intraoperative Factors

    A technically well-performed TKA will improve pain and restore motion and function to the diseased knee. However, certain intraoperative missteps or errors can hinder knee function and result in knee stiffness.

    Factors that limit knee flexion

    • Raising the joint line. Surgeons often raise the joint line to manage preoperative knee flexion contracture. [7] However, joint line elevation of more than 1 cm [8,9] may result in limited flexion due to impingement of the patella and tibial component or impingement of the posterior tibial tray and the posterior femur in flexion.
    • Increasing femoral offset. This can result from either under-resecting the posterior femoral condyles or implanting an oversized femoral component in the anteroposterior dimension. [10] The knee then has a tighter flexion than extension gap.
    • Creating anterior tibial slope. This error results in limited flexion both by preventing femoral rollback and by causing posterior tibial impingement on the femur during flexion.
    • Overstuffing the anterior knee compartment. Excessive patellar composite thickness after re-surfacing [9] or anterior malposition of the femoral component can result in limited flexion by increasing tension in the extensor mechanism during flexion.
    • Failing to balance sagittal gaps. A knee whose gaps are not well balanced is at risk for becoming stiff secondary to proprioceptive protective mechanisms that sense instability.

    Factors that limit knee extension

    • Under-resecting the distal femur. This error results in an extension gap that is narrower than the flexion gap, potentially creating a situation in which there is not enough space in full extension for the prosthetic components.
    • Flexion-malposition of the femoral component. Especially in posterior-stabilized designs, flexion malposition of the femoral component results in premature impingement of the polyethylene and the femoral component as the knee approaches full extension.

    Factors that limit both extension and flexion

    • Inadequate tibial resection
    • Insertion of an excessively thick tibial polyethylene
    • Incomplete removal of posterior femoral osteophytes. Failure to remove posterior femoral osteophytes may result in limited flexion due to impingement of the tibial component during flexion and may limit extension by tenting the posterior capsule, thereby increasing tension in extension.

    ICJR: What can the surgeon do preoperatively to minimize the risk of knee stiffness after TKA?

    Dr. Otero: Setting expectations preoperatively plays a critical role in a patient’s outcome. Total knee arthroplasty can be anxiety provoking but knowing what to expect can help a patient focus on healing and rehabilitating. In this regard, preoperative total joint education classes have significantly improved patient-reported outcomes after surgery and have been shown to reduce the need for manipulation under anesthesia after TKA. [11]

    As we move toward more technologically centered education platforms, surgeons continue to develop creative methods to effectively disseminate information. In a recent study, arthroplasty surgeons utilized a suite of YouTube videos to create a virtual hospital experience for patients undergoing total joint arthroplasty. This intervention significantly reduced patients’ preoperative anxiety scores. [12]

    Regardless of the method chosen to educate patients, it is important for the surgeon to understand and help set the patient’s goals and expectations. Numerous studies have shown that patient expectations correlate with satisfaction postoperatively. [13]

    ICJR: Are there intraoperative techniques to reduce the risk of postoperative stiffness?

    Dr. Otero: Surgical errors that result in restricted motion after TKA are outlined above. Numerous methods have been devised that attempt to offer patients an advantage with regard to knee motion and clinical outcomes postoperatively, including patient-specific instrumentation, [14] computer-assisted navigation, [15] robot-assisted surgery, [16] and high-flex knee designs. [17] To date, however, these methods have failed to demonstrate a consistent clinical advantage over traditional techniques in routine TKA. There is no substitute for a technically well-planned and effectively executed surgery.

    Some authors advocate for capsular and wound closure with the knee in flexion as a means to improve knee flexion after TKA. A recent review summarized results from 7 studies comparing knee closure in flexion and extension. [18] In general, patients with knee closure in flexion achieve earlier motion milestones and faster clinical recovery compared with those with knee closure in extension. However, there is no evidence to suggest a long-term benefit. [18]

    ICJR: How about postoperatively: What can the surgeon do at that point to minimize stiffness?

    Dr. Otero: Patient participation in physical therapy is the most important aspect of care after TKA. The surgeon must understand the patient’s barriers to participation, such as awareness of its importance, geographic location, transportation, family support, and pain control. Multiple forms of physical therapy have been shown to be effective, including:

    • Outpatient, guided-motion programs
    • Home based, self-directed physical therapy [19]
    • Web-based at home programs [20]
    • Automated text-message-guided programs with close follow-up [21]

    A typical physical therapy regimen after TKA begins on the date of surgery. Patients are taught isometric quadriceps-engaging exercises and active range of motion strategies. Patients are encouraged to take short walks each hour with the assistance of a walker.

    After 2 weeks, the wound should be healed, and passive range of motion can be incorporated into the routine. As pain and confidence improve, patients are encouraged to take walks for longer distances and wean away from their assistive device. By 6 weeks, pain and stiffness should continue to resolve, and isokinetic quadriceps and hamstrings strengthening exercises can be incorporated.

    By 3 months, most TKA patients should have achieved greater than 90% of their ultimate knee motion and pain control. They can expect slow gains for up to 1 year postoperatively.

    It is the surgeon’s role during this period to coach and encourage the patient while also appropriately treating pain.

    ICJR How do you manage the patient who presents with stiffness following TKA?

    Dr. Otero: The workup for a stiff knee after TKA begins with a thorough history. It is important to understand all of the potential contributing factors involved in the patient’s stiffness. For example, a young patient with post-traumatic osteoarthritis with a stiff knee preoperatively might expect less ultimate motion after surgery than a patient with idiopathic osteoarthritis.

    Knowledge of the timing of surgery is also important. A patient with 90° of flexion at 3 months postoperatively may have different treatment options than a patient with restricted flexion 1 year out from surgery. The physical examination is helpful in determining the degree of stiffness and whether there is restriction in flexion, extension, or both. There may also be a paradoxical coronal instability as the knee flexes.

    Plain radiographs are also critically important. The surgeon must evaluate films for the common intraoperative errors noted above: If a surgical error has occurred, the role of physical and manual therapy will be limited. Plain radiographs are also useful for evaluating knee alignment and implant fixation.

    Finally, every patient who presents to the clinic with a stiff and painful knee warrants a workup for infection, with evaluation of inflammatory markers and knee aspiration.

    A patient who presents with stiff knee that appears appropriately aligned, well fixed, and is not infected may require further treatment to achieve improved motion.

    Patients should be evaluated by 6 weeks postoperatively. Those who have not achieved greater than 90° of flexion should undergo an aggressive physical therapy regimen with passive and active assisted range of motion exercises. Patients must be followed closely. Those who fail to progress should be offered manual manipulation of the knee under anesthesia.

    There is some variation in recommendations regarding the timing of manipulation, [10,22] but authors generally agree that manipulation should be performed within 3 months of TKA. An effective protocol for evaluation, manipulation, and post-manipulation therapy is outlined by Keating et al, [23] who demonstrate a gain in flexion of roughly 35° that is maintained at 5-year follow-up.

    ICJR: When do you decide to perform a revision procedure?

    Dr. Otero: Revision TKA may be considered for knees that present with stiffness after 3 months postoperatively or for knees that are stiff despite manipulation under anesthesia. Outcomes are generally good for revision in the setting of loosening, oversized components, or malalignment. However, revision for stiffness per se has less-predictable results. This is likely because revision may not address the underlying condition that caused the stiffness.

    Arthrofibrosis is a pathologic condition resulting in knee stiffness, although it presents infrequently after TKA. It is characterized by restricted range of motion and knee pain despite normal surgical and radiographic parameters. Arthrofibrosis is believed to be the result of an inflammatory process that causes abnormal proliferation of myofibroblasts in periarticular collagen-containing soft tissues. When arthrofibrosis is suspected, the surgeon may consider quadricepsplasty, lysis of adhesions, or revision surgery. [24,25]

    In a small series focusing on revision for stiffness after TKA, 3 patients who underwent revision TKA for arthrofibrosis had no gain in motion at final follow-up. [11] In a more recent series of 46 knees revised for arthrofibrosis, there was a significant gain in both flexion (15°) and extension (8°) at minimum 2-year follow-up, but complication and reoperation rates were high. [26] Therefore, it is important for the patient to be made aware of the risks involved prior to any aggressive treatment for arthrofibrosis.

    In conclusion, stiffness after TKA is a complication with many potential contributing factors. Understanding the patient’s preoperative level of function, range of motion, and current goals will help guide evaluation and treatment.

    When caring for a patient with knee stiffness, it is important for the surgeon to perform a thorough history and physical exam and to recognize the common surgical errors that can restrict motion of the knee. Pain control and physical therapy in the early postoperative period are paramount to a successful outcome, and web-based and app-guided physical therapy programs are gaining popularity among patients and surgeons. Manipulation of the knee under anesthesia can improve motion significantly if performed early, and surgical treatment should only be performed if the underlying cause of knee stiffness can be addressed by surgery.

    Author Information

    Jesse E. Otero, MD, PhD, is from the OrthoCarolina Hip and Knee Center, Charlotte, North Carolina. He is also an Assistant Professor with Atrium Health, Charlotte, North Carolina.

    Disclosures: Dr. Otero has disclosed that he is a consultant for DePuy Synthes.


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