A comprehensive history is crucial when evaluating patients with complaints after TKR. All problems that preceded the knee replacement should be documented, including antecedent operations, date of the index TKR, and any perioperative problems or delays in recovery or rehabilitation. Persistent swelling or drainage after the knee replacement raises the index of suspicion for infection.⁴ It is important to determine whether primary wound healing occurred and whether the patient had an initial period of pain relief after the TKR surgery. It is helpful to determine whether the patient’s presenting symptoms are the same as the symptoms before the TKR. If the patient’s current symptoms are identical to the preoperative symptoms, the original diagnosis of the knee being the cause of the patient’s pain must be carefully reevaluated. Medical comorbidities should be determined, including the presence of diabetes mellitus, a neurologic or vascular disease, a septic focus, and an immunocompromised state.

One must initially establish the exact nature of the patient’s complaint. Although pain is typically given as the chief complaint, specific questioning may reveal that the problem is actually weakness, giving way, or swelling. Giving way may be a sign of ligamentous instability, patellofemoral instability, component malalignment, or muscle weakness or inhibition. Weakness may be a result of spinal stenosis or muscle atrophy. After pain has been established as the principal problem, the exact location of the pain should be sought and localized as precisely as possible. Radicular pain may arise from lumbar spine disease. Medial knee pain may result from hip disease. Pain in the thigh or calf can be of vascular or neurologic origin. Pain that is well localized to the anterior portion of the knee is often of patellofemoral origin. Posterior knee pain may be related to a popliteal cyst, deep venous thrombosis, or pseudoaneurysm. Pain that is consistently localized to a small area may result from a neuroma⁵ or chronic bursitis. Typically the pain is described as related to the knee joint in the region of the medial and lateral joint lines.

Factors that aggravate or alleviate the pain should be sought. Pain associated with weight-bearing activities may indicate mechanical loosening. Pain that is constant, that is unrelated to activity, and that occurs at night may be related to infection. Start-up pain that worsens with the first few steps is typical of loosening and may represent inadequate ingrowth of a cementless prosthesis or early loosening of a cemented prosthesis. Pain associated with inadequate ingrowth of a cementless prosthesis is often present within the first year, whereas pain associated with loosening of a well-aligned noninfected cemented prosthesis occurs much later.⁶

The patient should be questioned regarding functional activities. The distance or time a patient reports being able to walk should be recorded, along with the use of ambulatory devices. It is helpful to ask about the patient’s ability to ascend and descend stairs and to know which leg is used to go up or down first. The ability of the patient to arise from a chair and symptoms typical of instability during walking are important to question the patient about.

The patient should be queried regarding his or her expectations after knee replacement. The patient’s problems preoperatively should be compared with his or her anticipated results and current symptoms and function. The patient’s employment history should be recorded and taken into consideration. Patients receiving workers’ compensation benefits have been reported to have less predictable results after TKR. Any ongoing or pending
legal action regarding the patient’s knee condition should be questioned and recorded. Underlying depression or psychiatric disease should be evaluated. Current or previous treatment with antidepressants or other neuropsychiatric medications should be recorded. Patients with a preoperative mental composite score of less than 50 on the Short Form-36 Questionnaire are at increased risk for less improvement in their physical function score after TKR.

A thorough physical examination of the patient with pain after TKR should not be limited to the knee, as knee pain can be associated with lumbar spine, hip, or retroperitoneal pathology. Therefore, examination of the spine, hip, and abdomen is necessary in addition to the knee. It is useful to begin with the examination of the extrinsic causes of knee pain. Careful examination of the lumbar spine is particularly important if there is any radicular component to the patient’s pain. Examination of the hip is mandatory and should include range of motion and whether motion of the hip reproduces pain in the knee. Gait abnormalities, limb length inequality, hip girdle weakness, or fixed deformity of the hip should be sought. If range of motion of the hip is limited or other aspects of the hip examination are abnormal, radiographic examination of the hip is required. In some instances, injection of local anesthetic into the hip and determining whether this alleviates the patient’s knee pain can be helpful. Examination of the patient’s feet should include evaluation for evidence of peripheral neuropathy. Hypersensitivity of the limb associated with cool, shiny skin may indicate reflex sympathetic dystrophy. Absence of ankle deep tendon reflexes may indicate lumbar spine disease. Absent pulses may indicate peripheral vascular disease and often warrant noninvasive arterial duplex scanning. Finally, be sure to examine the foot and ankle alignment, as hindfoot or forefoot deformities can place increased stresses on the knee.

Examination of the knee joint often begins while observing the patient’s walk with and without supportive aids. Varus or valgus alignment of the knee may indicate ligamentous instability, component loosening or subsidence, or component malpositioning. Patients with hyperextension when weight-bearing may have posterior cruciate insufficiency or excessive wear of the posterior aspect of the polyethylene insert. The knee should be evaluated for erythema, edema, or an intra-articular effusion. Point tenderness to palpation at the joint line may be indicative of impingement of an underlying prominence such as an unresected osteophyte, a cementophyte, or an overhanging implant. Point tenderness and inflammation about the medial aspect of the tibia are often indicative of pes anserine bursitis. Point tenderness away from the joint line, with a positive Tinel sign and elimination of the point tenderness by a local injection indicates a neuroma.⁵

Active and passive range of motion of the knee replacement should be recorded. The maximum flexion and extension should be compared with preoperative values measured before the index knee replacement. The presence of crepitus with motion should be noted. The knee should be examined for a fixed flexion contracture or an extensor lag. An audible pop that occurs as the knee moves from flexion into extension is termed patellar clunk syndrome and results from a soft-tissue nodule at the superior pole of the patella.⁷ The audible pop results from the soft-tissue nodule popping into the trochlear groove.⁷

Knee stability is determined by static ligament testing. A TKR typically approximates the stability of a normal knee with mild anterior cruciate instability.⁸ Ligament competence in full extension and at 30° and 90° of flexion should be evaluated. Laxity to stress testing is typically recorded as 1+, 2+, and 3+, with notation of whether there is a firm end point. Sagittal plane laxity (anterior and posterior translation of the tibia on the femur to stress) should also be evaluated. Pseudolaxity is created by component collapse and should not be confused with ligament insufficiency.

In patients with symptoms after TKR, a detailed examination of the patellofemoral joint is important because patellofemoral pathology is the most common cause of additional surgery after TKR.⁹ Determine the competence of the extensor mechanism by evaluating the strength of knee extension and the presence of an extensor lag. Patellar tracking should be observed during passive motion and active motion. The presence of patellar tilting, crepitus, or clunking should be sought. Patellar mobility should be assessed in full extension and slight flexion. A positive apprehension sign is indicative of patellar instability, whereas decreased patellar mobility may be associated with patella baja or fibrosis and scar formation. The medial and lateral aspects of the patella should be palpated for patellar tenderness. Rotational abnormal alignment of the femoral or tibial components may be difficult to observe during examination of the knee.¹⁰ If present, malrotation of the components may be manifested by patellofemoral instability.

A complete radiographic evaluation is necessary to assess a painful TKR. The patient’s preoperative radiographs may be helpful as TKR for early-stage osteoarthritis is a known risk factor for continued pain and lower satisfaction following arthroplasty.¹¹ Initial postoperative radiographs should be reviewed for radiolucent lines at the bone-cement interface or the implant-bone interface. A careful review of sequential radiographs is an important part of evaluating a symptomatic TKR. Radiolucent lines are a common finding after cemented TKR.¹² Radiolucent lines that are noncircumferential and observed over only
a minority of the interface are not diagnostic of loosening.¹² Radiographic evidence of loosening is defined as a radiolucency that is progressive in serial X-rays or circumferential and larger than 2 mm at either the cement-prosthesis or bone-cement interface. Component subsidence or change in position is diagnostic of implant loosening. A radiolucent line that is present at only a portion of the interface (especially in zones I and IV of the tibial component), is less than 1 mm in width, and is not progressive on serial radiographs does not indicate loosening of the prosthesis and is most likely not the etiology of the patient’s pain. A radiolucency that has developed and progressed over a short period has an entirely different meaning than one that was present on the immediate postoperative X-ray and has not progressed.

Routine radiographic examination should include a minimum of three views: a coronal anteroposterior (AP) view obtained with the patient bearing weight on the limb, a lateral view taken with the knee flexed approximately 30°, and a patellar axial view with the knee flexed between 30° and 45°. The femoral interface is examined best in the lateral view, whereas both the AP and lateral views can be helpful when examining the tibial interface. Many believe that the bone-implant interface is more difficult to assess in cementless TKRs. Fluoroscopic examinations can be quite helpful to ensure optimal visualization of the interface by placing the X-ray beam tangential to the interface being examined (Fig. 62-1).¹³ The location of the X-ray beam differs in the lateral plane when examining the femoral interface and the tibial interface.¹⁴ Some authors have advocated using fluoroscopy to realign the X-ray beam when examining the interface at the anterior femoral flange and the posterior condyles interface (Fig. 62-2).¹³ Fluoroscopic
examination is also helpful to examine the tibial bone interface in the AP plane.

Alignment of the limb and each individual component should be radiographically determined and may be best evaluated on long-leg, standing hip-knee-ankle radiographs. These may be particularly helpful if malalignment of the components is suspected in the coronal plane. The femoral component should ideally be aligned 90° to the mechanical axis of the limb. The tibial component should be oriented at 90° to the anatomic axis of the tibia. The anterior flange of the femoral component on the lateral radiograph should be parallel to the anterior cortex of the femur. The orientation of the tibial component on the lateral view differs based on the type of component used. In a posterior cruciate-retaining component, the tibial component typically has approximately 7° of posterior slope. In a cruciate-substituting component, the tibial component is implanted between 0° and 3° of posterior slope. The rotational alignment of the prosthetic components is difficult to determine with plain radiographic examinations. If malrotation of the femoral or tibial component is suspected, obtaining a computed tomographic scan of the knee can be quite helpful.¹⁰ The rotational alignment of the femoral component in relation to the transepicondylar axis (Fig. 62-3) and the tibial component in relation to the tibial tubercle can be determined.¹⁰ This technique provides a noninvasive method for quantitatively determining the rotational alignment of the tibial and femoral components on a standard computed tomographic scanner and can be useful for patients with patellofemoral instability.¹⁰