Hip precautions are temporary movement restrictions prescribed following a total hip replacement (total hip arthroplasty). The specific rules depend directly on the surgical technique used. While some modern approaches are muscle-sparing, the traditional posterior approach requires a specific protocol to protect the new joint. These safety measures, known as posterior hip precautions, are implemented immediately after surgery to stabilize the hip. The goal is to prevent the prosthetic femoral head from coming out of the acetabular socket, a complication known as hip dislocation.
The Three Cardinal Rules of Posterior Hip Precautions
Posterior hip precautions center around avoiding three specific movements that create instability. The first restriction is avoiding hip flexion beyond 90 degrees, meaning the knee should never be lifted higher than the hip joint. This limit prevents the thigh from compressing the prosthetic components against the posterior capsule.
The second rule prohibits adduction, which is crossing the operated leg past the body’s midline. This action can force the femoral head out of the back of the socket. Patients are advised to keep a small distance between their knees at all times to avoid this.
Finally, patients must avoid internal rotation of the operated leg, which is turning the toes inward toward the opposite leg. Internal rotation, especially combined with hip flexion, places maximum strain on the posterior soft tissues. Keeping the toes pointed forward or slightly outward maintains a safer alignment.
Understanding the Risk of Dislocation
The necessity of these precautions stems from the surgical technique used in the posterior approach. To access the hip joint, the surgeon makes an incision at the back of the hip. This requires temporarily cutting or detaching soft tissues, most notably the short external rotator muscles and the posterior joint capsule.
These soft tissues, including muscles like the piriformis and obturators, normally provide stability to the hip joint. Once cut, they need time to heal and regain strength. Until this healing occurs, the hip is vulnerable to a posterior dislocation, where the ball of the new joint pops out the back of the socket.
The three restricted movements—flexion, adduction, and internal rotation—mimic the combined forces that leverage the femoral head out through this weakened posterior area. Adhering to the precautions gives the surgically repaired capsule and muscles time to scar down and provide natural stability. This protection is a direct response to the biomechanical changes caused by the surgical access route.
Practical Strategies for Daily Living
Sitting and Toileting
For sitting, patients must use chairs with firm, elevated seats that keep the hips higher than the knees, ensuring the hip flexion angle stays under the 90-degree limit. Low couches or standard car seats often require a cushion for elevation. A raised toilet seat is recommended to maintain the hip angle above 90 degrees.
Dressing
Getting dressed safely involves using long-handled assistive devices, such as a reacher or shoehorn, to avoid bending forward to reach the feet. When putting on clothes, the operated leg should always be dressed first and undressed last, minimizing excessive hip flexion. Elastic shoelaces or slip-on shoes can also eliminate the need to bend over.
Sleeping
When sleeping, it is safest to lie on the back. If sleeping on the side is necessary, the patient must lie on the non-operated side. An abduction pillow or several regular pillows must be placed between the legs to prevent the operated leg from crossing the midline.
Car Mobility and Turning
Entering and exiting a car is best accomplished by backing up to the seat, sitting down while keeping the knees apart, and then swiveling the entire body as a unit. The car seat should also be reclined as far as possible to reduce the hip flexion angle while riding. When turning while standing, the patient must lift their feet and take small steps, avoiding twisting the torso or rotating the hip inward.
Timeline for Following Precautions
The duration for following posterior hip precautions is determined by the surgeon and physical therapist, but a common timeframe is between six and twelve weeks following the procedure. This period allows the soft tissues, external rotators, and joint capsule manipulated during surgery to heal sufficiently. During this time, the hip gains enough initial stability to begin tolerating a greater range of motion.
The length of the restriction depends on the quality of the soft tissue repair and the patient’s individual healing rate. Once the initial healing phase is complete, the physical therapist will guide the patient through a gradual process of relaxing the restrictions. Continued physical therapy is important for strengthening the muscles around the hip, which ultimately provides the long-term, dynamic stability for the new joint.