Total knee replacement (TKR) surgery is a common procedure intended to relieve pain and restore movement in a damaged knee joint. While the surgery replaces the joint, success is measured by regaining knee flexion, or the ability to bend the knee. This range of motion is paramount for performing daily activities like walking, climbing stairs, and sitting comfortably. Achieving adequate flexion requires a dedicated, active partnership between the patient and the rehabilitation team.
Establishing Realistic Flexion Goals and Timestones
Regaining a functional range of motion (ROM) requires setting specific targets based on necessary daily movements. A patient needs approximately 90 to 95 degrees of flexion to sit down and stand up from a regular chair. Achieving 100 to 110 degrees is considered the minimum threshold for performing basic activities like walking and climbing stairs.
More demanding actions, such as getting on and off a bicycle or sitting in a low chair, require a greater bend, often between 110 and 125 degrees. The recovery journey follows a general timeline, though individual progress varies widely. The initial goal is to achieve at least 90 degrees of flexion by the end of the first week post-surgery.
By weeks two to three, the expected flexion milestone increases to at least 100 degrees. The period between four and six weeks typically aims for 110 to 120 degrees, allowing for optimal function in most daily tasks. These milestones serve as benchmarks guiding rehabilitation efforts.
Essential At-Home Exercises for Increasing Knee Bending
The cornerstone of post-TKR recovery is the consistent performance of prescribed at-home exercises, focusing on both passive and active range of motion. Passive Range of Motion (PROM) exercises use an external force, such as gravity or a strap, to move the knee beyond what the muscles can achieve alone. The supine heel slide is a foundational PROM exercise, performed while lying on the back and slowly pulling the heel toward the buttocks to bend the knee.
To increase the stretch, a towel or strap looped around the foot can gently pull the heel further toward the body, applying controlled overpressure. These sustained stretches should be held for 10 to 30 seconds to allow soft tissues to lengthen. Another effective PROM technique is the gravity-assisted stretch, which involves sitting on a high surface with the operated leg dangling down.
The weight of the lower leg and foot provides a constant, low-load stretch, which can be intensified by placing the non-operated foot on top of the operated ankle for gentle added pressure. Active Range of Motion (AROM) exercises use the patient’s own muscle strength to move the joint. Seated knee bends, performed while sitting on the edge of a chair, involve actively sliding the heel back and forth to bend and straighten the knee.
An important technique is Active-Assisted Range of Motion, where the non-operated limb helps the operated one. For instance, the non-operated foot can be placed behind the operated ankle to push it into greater flexion. This combination of active muscle use and gentle assistance helps build strength while incrementally increasing bending capacity.
Consistent practice is paramount, with many physical therapists recommending multiple short sessions throughout the day rather than one long session. Patients must distinguish between the mild discomfort of tissue lengthening and sharp, intense pain, which should be avoided. Performing 10 to 15 repetitions or holding stretches for 10 seconds, multiple times a day, prevents stiffness from settling in.
Specialized Techniques for Overcoming Flexion Plateaus
If a patient diligently follows their home exercise program and physical therapy but experiences a stall in progress, known as a plateau, medical interventions may be necessary. One technique is the Continuous Passive Motion (CPM) machine, a device that gently and continuously moves the knee through a pre-set range of motion. While primarily used immediately post-operatively to prevent stiffness, some protocols may reintroduce the CPM machine to manage a difficult plateau.
When stiffness is recalcitrant, the physical therapist may employ manual stretching techniques more aggressive than what the patient can safely perform at home. These hands-on techniques, such as joint mobilizations, involve applying specific, high-intensity forces to the joint capsule to stretch surrounding scar tissue. This is done with careful monitoring to break through restrictions without causing harm.
If these measures fail, a final option is Manipulation Under Anesthesia (MUA), a non-surgical procedure performed by the orthopedic surgeon. The patient is placed under anesthesia, allowing the surgeon to forcefully bend and straighten the knee, breaking up internal scar tissue (arthrofibrosis) that restricts movement. MUA is most effective when performed relatively early, ideally within three months after surgery, as older scar tissue is more rigid and less responsive.
MUA is considered a last resort, used only when stiffness significantly limits function and has not responded to conservative treatment. Following the manipulation, the patient must immediately resume an aggressive physical therapy schedule to maintain the newly gained range of motion.