Total Hip Arthroplasty (THA), commonly known as hip replacement, is a highly successful surgical procedure designed to replace a damaged hip joint with an artificial implant. This operation is performed to alleviate pain and restore mobility, often resulting from advanced arthritis or injury. While the new joint is designed to be durable and functional, its mechanical nature requires patients to adopt new habits and permanently avoid certain movements and activities. Adhering to these lifelong precautions is fundamental to protecting the artificial joint, preventing dislocation, and ensuring the long-term success of the implant.
Core Movements to Permanently Avoid
One of the most critical mechanical rules for patients, particularly those who undergo the traditional posterior surgical approach, involves the 90-degree rule. This principle dictates that the hip should never be flexed beyond a 90-degree angle, which is the point where the thigh is parallel to the floor. Bending the hip past this point, such as when sitting in a very low chair, deep squatting, or bending over to pick up an object from the floor, forces the joint into an unstable position.
Exceeding this 90-degree flexion limit creates a high risk for dislocation. To maintain a safe angle, patients must use assistive devices like long-handled reachers for items on the ground and utilize elevated seats for chairs and toilets. The goal is to always keep the knee lower than the hip when seated, which keeps the joint in a position of stability.
Another movement that must be permanently avoided is crossing the surgical leg over the midline of the body, a motion known as adduction. Crossing the legs while sitting, or even crossing the ankles when lying down, places a shearing and rotational force on the implant. This action can lever the ball out of the socket.
Internal rotation, or twisting the operated leg inward so the toes turn toward the opposite leg, also puts the artificial joint in a vulnerable position. This twisting motion stresses the posterior soft tissue structures that were disturbed during surgery. To prevent this, patients must pivot their entire body when turning, instead of twisting at the hip. They should also sleep with a pillow positioned between their legs to maintain proper alignment.
Long-Term Activity Limitations
Patients must adopt long-term limitations concerning activities that create excessive impact or stress on the prosthetic components. High-impact sports, such as running, jogging, high-impact aerobics, and contact sports like basketball or football, should be permanently avoided. These activities subject the hip to repetitive, high-magnitude forces that accelerate the wear and tear of the polyethylene (plastic) liner within the implant.
The abrasive effect of high-force, repetitive loading creates microscopic debris from the plastic or ceramic bearing surfaces. Over many years, this debris can trigger an inflammatory response that leads to osteolysis, which is the breakdown of the bone surrounding the implant. This bone loss can cause the implant to loosen.
Activities that involve heavy, repetitive lifting, particularly in an occupational or intense recreational setting, also place extreme and sustained stress on the implant. While moderate lifting is generally acceptable after full recovery, continually lifting loads that place excessive strain on the joint may compromise the long-term integrity of the bone-implant interface.
Activities with a high fall risk, such as rock climbing or skiing on difficult terrain, should be permanently avoided. A fall can result in a periprosthetic fracture, which is a break in the bone around the hip replacement components. These fractures are often severe and require extensive surgery, representing one of the most serious complications for a patient with a hip implant. Patients should instead focus on low-impact alternatives like swimming, walking, and stationary cycling to maintain fitness without compromising implant longevity.
How Surgical Approach Modifies Restrictions
The specific surgical technique used significantly modifies the permanent restrictions a patient must follow. The traditional posterior approach, which involves making an incision at the back of the hip, requires the temporary detachment of some muscles and tendons. Because these soft tissues are the primary stabilizers of the joint, this approach necessitates adherence to the 90-degree rule, avoidance of crossing the legs, and elimination of internal rotation to prevent dislocation.
Conversely, the direct anterior approach is considered a muscle-sparing technique, accessing the joint through an interval between muscles rather than cutting them. This preservation of the posterior soft tissues provides immediate joint stability, which often allows for the relaxation or complete elimination of many traditional hip precautions relatively early in the recovery phase. Patients who undergo the anterior approach may be cleared to bend past 90 degrees or sleep without an abduction pillow much sooner than those who had a posterior procedure.
However, even with the anterior approach, patients are still typically instructed to avoid the high-impact activities that accelerate implant wear. The decision to lift or eliminate any specific movement restriction is always patient-specific and rests with the orthopedic surgeon. The surgeon considers factors such as the patient’s bone quality, the type of implant used, and the security of the components to determine the final, personalized long-term precautions.