A flexion contracture is a permanent inability to fully straighten a joint. It happens when the soft tissues around a joint, including muscles, tendons, ligaments, or skin, shorten and stiffen to the point where they physically prevent the joint from extending to its normal range. The joint gets stuck in a bent position, and no amount of effort can straighten it completely.
What Happens Inside the Joint
A contracture is essentially a form of scarring in the soft tissues surrounding a joint. When a joint stays in one position for too long, the tissues around it begin to remodel. This process starts faster than most people realize. Protein production within muscle fibers drops within just six hours of immobilization. Within 24 hours, muscle fibers begin to physically shorten. By 48 hours, excess collagen starts infiltrating the connective tissue around the muscle, making it stiffer and less elastic.
Over time, these changes become self-reinforcing. The shortened tissues hold the joint in a flexed position, which causes even more shortening. The brain also adapts: prolonged disuse triggers changes in how the nervous system recruits the muscles around that joint, making it progressively harder to voluntarily move the joint even if the tissues were freed up. What starts as a reversible tightness can become a permanent structural change.
Common Causes
The single most common cause of flexion contracture is immobilization. Any situation that keeps a joint still for an extended period puts you at risk: wearing a cast for several weeks, being hospitalized for a severe injury or surgery, or spending long stretches in bed or a wheelchair. In institutionalized older adults, one study found that 71% of those who were immobile had at least one joint contracture, while every mobile patient remained contracture-free.
Neurological conditions are another major driver. Stroke, cerebral palsy, and spinal cord injuries disrupt the signals between the brain and muscles. This can cause sustained involuntary muscle contraction (spasticity), which holds the joint in a bent position. Left untreated, that spastic joint eventually develops a true contracture. After spinal cord injury specifically, 66% of patients develop at least one contracture within the first year. The rates vary by joint: shoulders are affected in 43% of cases, wrists and hands in 41%, ankles in 40%, elbows in 33%, and hips in 32%.
Burns cause a distinctive type of contracture through direct tissue damage. Thermal injury destroys skin and the tissues beneath it, and as scar tissue forms it shrinks and constricts, pulling the joint into a fixed position. Inherited conditions like muscular dystrophy and congenital muscle disorders can also lead to contractures by creating chronic imbalances between opposing muscle groups. Even age-related muscle loss can contribute: as people lose strength and spend more time sitting, the hip flexors shorten over months and years, leading to hip flexion contractures.
How It Affects Movement
A flexion contracture doesn’t just limit one joint. Your body compensates in ways that change your entire movement pattern. A knee flexion contracture, for example, forces you to walk differently. Research on adults with restricted knee motion found a consistent set of compensations: the hip and ankle on the affected side work overtime, increasing their range of motion to make up for the stiff knee. The muscles at the back of the thigh and hip activate more intensely than normal.
The timing of each step also changes. The push-off phase before the foot leaves the ground gets shorter, while the swing phase gets longer on the affected side. This creates an asymmetric gait that slows walking speed. At a knee restriction of around 30 degrees, walking speed drops measurably compared to unrestricted movement. Over time, these compensations can strain other joints, creating secondary pain in the hip, ankle, or lower back.
How Contractures Are Measured
Clinicians measure contractures using a goniometer, a protractor-like device placed along the joint. In a healthy joint, full extension is recorded as 0 degrees. The more a contracture prevents straightening, the higher the number. A knee that can only straighten to 25 degrees from full extension, for instance, has a 25-degree flexion contracture. That number becomes the baseline for tracking whether treatment is helping or the contracture is progressing.
Treatment Without Surgery
Physical therapy and stretching are the first-line treatments for flexion contractures, but the evidence for their effectiveness is more limited than many people expect. A large Cochrane review of stretching interventions found highly variable protocols, with stretch durations ranging from five minutes to 24 hours per day, applied anywhere from two days to seven months. The minimum stretch considered likely to have any effect on joint mobility was at least 20 seconds, repeated across multiple sessions. However, the overall finding was sobering: for each additional hour of total stretch time, there was essentially zero average improvement in joint range of motion.
This doesn’t mean stretching is useless. It may help prevent further loss of motion, and individual results vary depending on the cause, severity, and how recently the contracture developed. Newer contractures with less collagen buildup tend to respond better than chronic ones.
Splinting is another common approach. Dynamic splints use elastic tension to apply a constant low-level stretch to the joint while you wear them. Static progressive splints use a non-elastic mechanism that you manually tighten as the joint gradually gives. Both types have shown similar results in studies, with no clear winner. One comparative trial found that dynamic splints produced slightly better improvements in active extension (about 11.5 degrees) compared to static progressive splints (7.3 degrees), and they achieved this in fewer total hours of wear. But the difference was not statistically significant, meaning neither approach is definitively superior.
When Surgery Is Considered
Surgery becomes an option when conservative treatments have been given a fair trial without meaningful results. The general threshold is at least six months of formal physical therapy and dynamic splinting with no significant improvement, combined with a flexion contracture greater than 25 degrees that limits daily activities. Nonsurgical approaches like manipulation under anesthesia and minimally invasive joint releases tend to work only for mild contractures.
Surgical release involves cutting or lengthening the shortened tissues, whether that’s the joint capsule, tendons, or scar tissue, to restore the joint’s ability to extend. The specific procedure depends on which structures are responsible for the restriction. Recovery requires aggressive physical therapy afterward to maintain the range of motion gained during surgery, because the same biological forces that caused the original contracture will try to re-establish themselves if the joint isn’t kept mobile.
Prevention in Hospital and at Home
Because immobility is the primary cause, prevention centers on keeping joints moving. In hospital intensive care units, early mobilization protocols follow a structured progression. For the most critically ill patients, this means passive range-of-motion exercises (where a nurse or therapist moves the patient’s joints through their full range) twice daily for 10 repetitions per joint, repositioning every one to two hours, and elevating the heels to prevent ankle contractures. As patients improve, they progress through sitting upright in bed, transferring to a chair, and eventually standing and walking with therapist guidance.
Outside the hospital, prevention follows the same principle: move your joints through their full range regularly. For people at higher risk due to neurological conditions, arthritis, or prolonged sitting, daily stretching and range-of-motion exercises are protective. The body’s natural response to a painful or injured joint is to hold it still, which is exactly what sets the contracture process in motion. Gentle movement within a tolerable range, even during recovery from injury, is one of the most effective ways to keep that process from starting.