Stiffness is an uncommon but potentially debilitating complication following total knee replacement (TKR). The treatment of this condition remains difficult and controversial. We present the results of 13 patients who underwent open arthrolysis for stiffness. The mean time between TKR and arthrolysis was 14 months. The mean follow-up was 7.2 years (2 to 10). The mean range of movement prior to arthrolysis was 55°. This increased to 91°, six months after arthrolysis (p < 0.005). The improved range of movement was maintained during the follow-up period. No patient has required revision of their components. We have found arthrolysis to be a useful and successful approach to post-TKR stiffness.
Stiffness after total knee replacement (TKR) will occur in approximately 1% of patients.1 A fixed-flexion deformity increases the work required of the quadriceps during walking and the load at the patellofemoral joint. The knee must flex to 65° to walk along a level surface, 85° to negotiate a six-inch step and 95° to rise from a chair easily.2
The causes of stiffness include infection, poor positioning or over-sizing of the components, failure to balance the soft tissues and remove osteophytes, complex regional pain syndrome and loosening. Most cases will resolve with structured physiotherapy. Manipulation under anaesthetic may be helpful in the early treatment of resistant cases.3–6 However, once the scar tissue has matured, the best approach remains controversial. There has been increasing support for revision arthroplasty.1,7,8 Our approach to this problem is to perform an extensive open arthrolysis with selective polyethylene downsizing and/or patellar replacement as required. We here present our results of this technique.
Patients and Methods
The senior author (MJC) has used the Active uncemented total knee replacement (Australian Surgical Design and Manufacturer, Sydney, Australia) for all primary TKRs since August 1992. This is a hydroxyapatite-coated, posterior cruciate ligament (PCL)-retaining design, with a cemented polyethylene patellar component. The patients were assessed using the Knee Society score (KSS).9 Range of movement was measured and complications recorded. There were 1522 patients (2022 TKRs), of whom 500 underwent a simultaneous bilateral procedure.
Stiffness, which was sufficiently severe to warrant an open arthrolysis was found in 13 patients (0.64%). There were five men and eight women with a mean age of 65 years (50 to 78) at the time of the primary procedure; six had undergone simultaneous bilateral TKR, representing 0.6% of knees in the bilateral group, and had developed stiffness in one knee. Patellar replacement had been performed at the time of primary surgery in two of the 13 patients. There were no cases of infection (based on microbiological culture) and no cases of component malposition or malrotation. No patient underwent manipulation under anaesthesia or other surgical procedure before their arthrolysis.
All patients underwent an open soft-tissue arthrolysis. The procedure is performed with a tourniquet. The original scar is re-opened and the incision deepened to the capsule. The knee is opened medially and the thickened capsule excised from the joint. This capsular scar tissue can be up to 15 mm thick. Adhesions under the suprapatellar pouch are released. The scar tissue is removed from the medial gutter. A lateral release is performed to free the extensor mechanism and to allow access to the scar tissue in the lateral gutter and beneath the patellar tendon. We feel that by approaching the tendon from the lateral side, the tissue planes are easier to define as this is relatively virgin tissue. The patellar tendon can then be released. The scar tissue which tethers the patellar tendon may cause patella infera, and patellar height must be recovered to maximise recovery. After this release, we have found the patella can be everted without the need for a quadriceps snip, turn down, or osteotomy of the tibial tuberosity. The knee can then be flexed and the tibial insert removed to allow access to the posterior structures. The PCL is released in all cases. The popliteus tendon, and/or posterior capsule may require release in order to correct the fixed-flexion deformity. Downsizing the tibial insert may also help with this correction. Three inserts were downsized from 11.5 mm to 10 mm (10 mm is the thinnest insert in the Active knee system).
Patellar tracking is assessed and the patella resurfaced if there is concern about damage to the articular surface. This occurred in five patients. The knees are drained and closed in flexion. Continuous passive motion is started on the day of operation and rehabilitation commenced under the direction of a physiotherapist.
Statistical analysis of the data was performed using SPSS software (SPSS, version 10.0, Chicago, Illinois). The range of movement pre- and post-arthrolysis and the KSS were analysed using a paired t-test. The results were considered statistically significant if p < 0.05.
There was no difference between the pre-operative demographics of the arthrolysis subgroup and the total series (Table I⇓). The mean time from TKR to arthrolysis was 14 months (6 to 21). The mean follow-up was 7.2 years (2 to 10) after the primary TKR.
One patient required a repeat arthrolysis two years after the initial release. One knee became infected six years after implantation because of septicaemia following a spider bite. There was one death at seven years.
Before arthrolysis, the mean range of movement was 55° (20° to 75°) with a mean fixed-flexion deformity of 12.3° (0° to 25°) (Table II⇓). The range of movement at six months post-arthrolysis increased to a mean of 91° (58° to 110°), an improvement of 36° (p < 0.005). At the last follow-up (mean 7.2 years) the mean range of movement was maintained at 96° (75° to 115°) and only one patient had a fixed-flexion deformity of 5°.
The mean total KSS had significantly improved from a pre-TKR value of 103 to 147 (mean clinical score 78, mean functional score 69) prior to open arthrolysis (p < 0.005; Table III⇓). The mean KSS at follow-up after arthrolysis was 155 (mean clinical score 83, mean functional score 72). Thus, despite the limitations imposed by the stiffness of the knee, there was still a significant improvement in the total KSS after TKR in those patients who required open arthrolysis (p < 0.005; Table III⇓). At the latest follow-up there was no significant change in the Knee Society scores (p = 0.291). Despite the significant improvement in range of movement we were, therefore, unable to demonstrate a significant improvement in the KSS by performing the arthrolysis.
The incidence of stiffness after TKR appears to be low in published series at around 1%.1 There is still debate as to the definition, cause and treatment of these patients. Stiffness has been defined in various papers as being flexion of < 85°,10 an arc of movement of < 70°,11 a flexion contracture of > 15° or < 75° of flexion, or an arc of movement of < 45°.8 All the patients in our cohort fell within the definition of stiffness cited by Kim et al1 of an arc of movement < 75°.
The mean range of flexion in our series of 2022 knees was 116°. The arthrolysis group had a mean fixed-flexion deformity of 12.3° and a mean range of flexion of 55°. Other reports of open arthrolysis have had smaller groups with stiffer knees (mean arcs of movement 36° to 38°).1,7,12 Only three of our patients had a range of flexion of < 30°.
Technical problems in component sizing and positioning can cause stiffness after TKA.13 However, there will be a group that develops severe stiffness despite a correctly-sized and implanted prosthesis. This stiffness can be attributed to excessive scarring within the knee or arthrofibrosis.12 It has been suggested that some patients have a predisposition to scarring and this may be associated with heterotopic calcification around the knee.14 Interestingly, in our series, there were six patients with simultaneous bilateral TKRs who were stiff on one side but not on the other. Ries and Badalamente12 have shown an increased density of fibro-cartilaginous metaplasia within the scar tissue of the stiff knees. This may be caused by mechanical compression and post-operative rehabilitation has been indicated as a possible trigger.15 It is not clear why only a few patients have this excessive response.
The prevalence of complex regional pain syndrome one month after TKR may be as high as 21%,16 with an increase in pain and swelling in the limb and this will have a direct impact on how the patient rehabilitates. The chronically stiff knee may represent the end-stage of an unrecognised complex regional pain syndrome but this requires further investigation.
Manipulation under anaesthesia, arthroscopic release, open arthrolysis with polyethylene exchange, and revision TKR are all treatment options for patients with a stiff knee replacement. Manipulation has a role in the treatment of early stiffness and an improvement in range of movement is generally expected.5,6 However, those patients who benefit from an early manipulation may be different from those who develop a mature arthrofibrosis. Arthroscopic release also has a role in early cases and, in particular, for those patients with a patellar clunk.17 We feel that the extensive resection required to release mature scar tissue from the knee joint cannot be done arthroscopically. This is especially important when correcting a flexion contracture when it is necessary to perform a posterior release and capsulectomy.
Poor results following open arthrolysis have been reported7 and exchange of tibial insert has been questioned as a viable strategy for the treatment of patients with a stiff TKR.18,19 There is an interesting move towards revision TKR as the treatment of choice for these patients. The published results of revision surgery do show improvement in range of movement and pain scores although these improvements are modest.1,14 Our experience with these patients has been different. To the best of our knowledge, this is the largest reported series of open arthrolysis with the longest follow-up. No patient in our series has required revision surgery with its increased complications.
We feel that a meticulous open arthrolysis, with consideration of selective patellar resurfacing and/or tibial-insert downsizing, is a valid treatment strategy for this difficult and poorly understood problem. It gives a significant and sustainable improvement in range of movement. We feel that open arthrolysis is an effective and reproducible technique in the treatment of the stiff TKR and has good, long-term results.
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
- Received December 20, 2004.
- Accepted April 12, 2005.
- © 2005 British Editorial Society of Bone and Joint Surgery