Stiffness after total knee arthroplasty (TKA) is a frustrating problem for patient and surgeon alike. Few patients with substantial limitation of knee range of motion are satisfied with the result of their TKA. Depending on the definition of stiffness, somewhere between 1.5 and 3% of contemporary TKAs have limited postoperative range of motion. Although specific effort must be made to determine the reason for the stiffness following TKA, the fact remains that the precise cause remains poorly understood in the majority of cases (Figure 68.1A and B).

Select subgroups of patients do have a clear etiology for their postoperative stiffness, and it is critical to identify those patients as the results of treatment are predictably better. There are a multitude of small series that implicate one small technical factor or another as a cause of stiffness after TKA. Those include overstuffing the patella, a tight posterior cruciate ligament, flexion gap mismatch, component malposition, joint line elevation, poor postoperative pain control, and inadequate postoperative rehabilitation. Surgeons should be cautious about recommending revision surgery for stiffness if only one small problem is identifiable, as the results of additional surgery in such cases are likely to be modest.

One pragmatic approach to the painful TKA is to methodically look for extrinsic causes, intrinsic causes, and patient-specific causes for stiffness and pain. To do this most predictably it is useful to have a preset routine in which every patient with a stiff or painful TKA gets (1) a full-length hip-knee-ankle radiograph, (2) fluoroscopically positioned radiographs of the knee, and (3) serum erythrocyte sedimentation rate and C-reactive protein, and plan for (4) knee aspiration for cell count and culture.

Extrinsic causes for stiffness are those outside the knee joint itself and primarily focus on the hip and spine. It is not uncommon to get tunnel vision and keep thinking knee, knee, knee and in doing so overlook advanced hip arthritis or lumbar radiculopathy as the cause of knee pain and disability. The hip-knee-ankle radiograph builds in a reminder to check the hip in all of these cases.

Intrinsic causes for stiffness include infection, aseptic loosening or failure of ingrowth, and surgical technical errors. Infection is assessed with the sedimentation rate and C-reactive protein tests followed by knee aspiration. Infection presents a good news/bad news scenario where the good news is a clear cause for the stiffness and pain, whereas the bad news is the additional surgical intervention needed. Loosening of cemented components or failed ingrowth of uncemented components is most readily assessed with high-quality serial radiographs.

Patient-specific causes of stiffness include secondary gain problems (workers compensation, disability claims), poor pain tolerance, and arthrofibrosis related to an abnormal inflammatory response. Separate strategies must be developed if one chooses to reoperate on one of these patients with a presumed patient-specific cause of stiffness so as to not simply repeat the prior events that led to stiffness.

Document previous interventions or procedures that have been used to treat stiffness (i.e., manipulation under anesthesia, arthrolysis, polyethylene liner exchange, component revision).

A detailed preoperative assessment and critical appraisal of radiographs will determine whether one or both components need to be revised to address stiffness. Variables to consider include:

Acquiring operative reports and implant stickers is paramount if there is a plan to retain one or both implants to ensure modular options, and appropriate extraction tools are available if required.

The results of revision TKA for stiffness are unpredictable; however, most studies report a modest improvement in range of motion and patient-reported outcome measures.

Manipulation under anesthesia done either closed or arthroscopically is often useful for the patient who presents with early postoperative stiffness and occasionally useful for the patient with stiffness who presents late. Manipulation is typically done under a brief general anesthetic, and it is useful to have full muscle relaxation through pharmacologic paralysis during the manipulation. Care must be taken to gradually flex the knee and to avoid sudden forceful motions that could cause a femoral or patellar fracture. By holding the leg close to the tibial tubercle, as opposed to at the ankle, one minimizes the lever-arm and decreases the risk of iatrogenic fracture (Figure 68.2A and B). Typically, the knee is flexed over a 2- to 5-minute time period and it is helpful to listen carefully for the sound of intra-articular scar tissue slowly breaking. As long as one can hear scar tissue continuing to break free it is safe to continue applying pressure and pursuing additional flexion. If one chooses to manipulate a knee at more than 1 year postoperatively, then it is wise to consider doing that arthroscopically or at least assisted with arthroscopic instruments. For these very stiff knees one can make 2 or 3 arthroscopic portals around the knee and insert a standard knee scope sheath and trocar together. The sheath and trocar are then used to physically disrupt scar tissue by methodically re-establishing the suprapatellar pouch, the medial
and lateral gutters adjacent to the femur, and the retropatellar space behind the patellar tendon. Those maneuvers can be easily performed blindly without actually inserting the arthroscopic camera. Once the scar tissue has been freed bluntly with the sheath and trocar, the knee is progressively manipulated under anesthesia. Manipulation under anesthesia is predictably useful in regaining flexion but is both unpredictable and somewhat risky when attempting to regain extension. Although it may be useful in certain circumstances, manipulating a stiff knee in extension puts the distal femur at particular risk of fracture.