The Stiff Knee: A frustrating, post-operative challenge
One of the most frustrating surgical after effects for the patient, the physical therapist, and the surgeon is the development of a stiff knee following surgery. While, this may occur unexpectedly after almost any knee procedure, it is not an infrequent problem specifically after a total knee replacement.
Between 5% and 7% of patients develop stiffness in the knee post-operatively. In my experience with patients in physical therapy, post-operative knee stiffness is a more common after effect of total knee replacement (TKR) surgery, surpassing the combined prevalence of infection, thromboembolism and early mechanical failure. One study that supports this is one that reviewed over 5,000 TKRs performed in over 4,000 patients between 1997 and 2003. Manipulation under anesthesia was required in 399 cases (6.9%). Similarly, in another recent study it was reported that among over 1,000 consecutive TKR patients, 63 (5.3%) developed stiffness. Of the 56 patients in this study available for analysis, 46 patients required manipulation and 10 (0.84%) required revision surgery for stiffness.
Over the years, the definition of stiff TKR has changed reflecting patient and physician’s high expectations for function and range of motion (ROM) after surgery. Patients require a knee flexion of 65° to walk, 70° to lift an object from the floor, 85° for stair climbing, 95° for comfortable sitting and standing, and 105° for tying shoelaces, and 115° to squat and pick up an object.
In some of the literature, the definition of stiffness after TKR is a flexion contracture of 25° or a total arc of motion less than 45°. Other literature defines stiffness as a total arc of motion less than 70°. One final source defines stiffness as a flexion contracture greater than or equal to 10° or a total arc of motion less than 95°.
Many of these patients that meet these definitions for post-operative knee stiffness, especially those with severe limitation of ROM, have severe disabling pain that interferes with their activities of daily living and quality of life. As a consequence of the previously discussed issues, and despite the use of modern TKR implant designs that allow for high flexion, the relative frequency of stiffness still exists in many cases.
Stiffness after TKR is a multifactorial, poorly understood problem in which preoperative, operative and postoperative factors can be considered. Identification of predisposing factors allows surgeons to better address patients’ expectations for postoperative ROM.
Some research studies have reported that patients with a history of post-traumatic osteoarthritis, those who underwent a high tibial osteotomy, those with multiple knee surgeries, and those who present with a limited preoperative ROM are at an increased risk of developing postoperative stiffness. The role of obesity is controversial as to whether this is a cause of a patient developing postoperative stiffness.
Operative factors that could lead to stiffness after TKR can be categorized in the following groups: retained osteophytes in the posterior condyles, imbalance of the flexion and extension gaps, malalignment, improperly sized components and inaccurate patellofemoral joint reconstruction. These issues can often be detected on plain radiographs and can be differentiated from other sources of stiffness.
Postoperative factors potentially leading to knee stiffness include poor patient motivation and/or selection, deep infection, heterotopic ossification, pain management regimen and aggressive anticoagulation therapy which may result in the development of intra-articular hematomas with secondary stiffness.
Some patients who develop post-operative stiffness require manipulation under anesthesia to address this issue. The best candidate for maninpulation is a motivated patient with a restricted ROM detected within 3 months of surgery. A minimum of 90° of flexion is required to negotiate stairs and sit comfortably; therefore, patients who have failed to achieve at least 90° of flexion following surgery are candidates for manipulation.
In my experience with patients I have seen in physical therapy, manipulation has seemed to work better to correct restricted flexion than to overcome a flexion contracture. During manipulation, increased motion is achieved through mechanical lysis of intra-articular adhesions, thus manipulations that are performed within the first 3 months of surgery tend to be safer and more efficacious than those performed at a later time. In additional, the first manipulation tends to be more successful that subsequent ones.
It is paramount that the patient initiates an intensive physical therapy program after manipulation. Post-manipulation, patients typically participate in a physical therapy program with five visits per week for 2 to 3 weeks, followed by three visits per week for an additional 2 to 3 weeks. It is also crucial that patients perform home exercises , use cold packs and have good pain control.
Manipulation is successful in controlling pain and increasing range of motion in 75% to 90% of cases. Unfortunately, some patients, even a few without predisposing factors for stiffness will develop arthrofibrosis, a complication that is still poorly understood.
Overall, patients who get between 128 and 132 degrees of knee flexion seem to have good function for everyday activities. Anyone who engages in activities requiring kneeling, squatting, or sitting cross-legged may need additional rehab to obtain enough motion to accomplish these tasks.
Sarah Bicknell PT, MSPT, ATC