A contracture is the chronic loss of full passive range of motion in a joint. This restriction results from structural changes in the non-bony, or soft, tissues surrounding the joint. The condition prevents the joint from moving through its normal arc, leading to a fixed, often deformed, position.
Understanding the Mechanism of Contracture
The physical process of contracture involves a fundamental change in the cellular and structural makeup of soft tissues. Tissues that are normally elastic, such as muscles, tendons, ligaments, and the joint capsule, lose their pliability and are gradually replaced by inelastic tissue. This process, known as fibrosis, is characterized by the excessive production and accumulation of collagen within the connective tissue. The rigid, dense collagen fibers make the tissue thicker and less able to stretch, leading to shortening and hardening.
Myostatic shortening involves a reduction in the number of functional contractile units, called sarcomeres, within the muscle fibers. This shortening happens when a muscle is maintained in a consistently shortened position for an extended period, such as in a cast or splint.
This adaptation creates a self-perpetuating cycle: the lack of movement causes structural changes, and the structural changes further limit movement. The result is a mechanically fixed joint that cannot be fully straightened or moved without external force.
The Primary Causes and Contributing Factors
The most frequent cause leading to contracture formation is prolonged immobility or disuse of a joint. When a limb is kept static, such as during a long hospital stay, extended bed rest, or immobilization in a cast, the lack of movement deprives the soft tissues of the stretch necessary to maintain elasticity. This sustained lack of motion initiates the fibrotic process within days or weeks.
Neurological conditions represent another major category of contributing factors, often by causing muscle imbalance or tone abnormalities. Conditions like stroke, cerebral palsy, and spinal cord injury can lead to paralysis, weakness, or increased muscle tone, known as spasticity. The presence of high muscle tone or a sustained muscle contraction holds a joint in a fixed position, triggering structural changes over time.
Severe trauma, particularly deep burns, can also directly cause contractures through the formation of extensive scar tissue. This dense, shrunken scar tissue crosses the joint and acts as a physical tether, severely restricting the joint’s range of motion. Other factors include ischemic injury, where poor blood flow leads to tissue death and subsequent scarring, and certain inherited disorders like muscular dystrophy.
How Contractures Are Categorized
Contractures are commonly classified by their tissue origin: dermatogenic, myogenic, and arthrogenic types. Dermatogenic contractures originate in the skin and subcutaneous tissues, often resulting from burn scars or severe skin trauma. Myogenic contractures involve the muscle and its surrounding fascia, typically resulting from prolonged shortening or neurological issues.
Arthrogenic contractures are rooted in the joint itself, involving the joint capsule, ligaments, or articular cartilage. Contractures may also be classified by the systemic or local condition that triggered the tissue change. Neurogenic contractures stem from damage to the central or peripheral nervous system, disrupting the normal control of muscle tone and movement. Examples include Volkmann’s ischemic contracture, caused by inadequate blood flow, and Dupuytren’s contracture, where the fascia beneath the skin of the palm thickens and shortens, pulling the fingers into a flexed position.
Treatment and Rehabilitation Strategies
Early intervention is highly beneficial, as recent contractures respond better to conservative methods than advanced, fixed contractures. Non-invasive physical therapy is the foundation of management, including daily passive and active range-of-motion exercises.
Sustained stretching is applied through techniques like splinting, bracing, and serial casting to gradually lengthen the shortened tissues. Serial casting involves applying a cast that holds the joint at its maximum stretch, which is periodically removed and reapplied in a slightly more extended position over several weeks. When spasticity is a major contributor, botulinum toxin injections may be used to temporarily relax the overactive muscles, allowing for more effective stretching.
When conservative measures fail to achieve functional improvement, surgical intervention may be considered for fixed contractures. Surgical procedures typically involve releasing or lengthening the shortened structures, such as a tenotomy (cutting a tendon) or a fasciotomy (cutting the fascia). The goal of surgery is to physically restore the joint’s range of motion, but it must be followed by intensive physical therapy to maintain the gains and prevent recurrence.