What are the risks of joint replacement surgery? 

Joint replacement surgery is a highly successful and routine procedure, yet like any major operation, it carries a specific set of clinical risks that patients must understand before proceeding. While the vast majority of hip and knee replacements in the UK are performed without serious complications, being aware of the potential issues allows for better preparation and faster recognition of symptoms during recovery. These risks range from common, manageable side effects like bruising to rarer but more serious complications such as deep vein thrombosis or surgical site infections. Clinical teams follow strict NHS and NICE protocols to minimise these hazards, but the patient’s own health status and adherence to post-operative advice play a vital role in ensuring a safe outcome. Understanding these risks is not meant to cause alarm, but rather to empower you to take an active, informed role in your own surgical journey. 

What We’ll Discuss in This Article 

• The most common immediate risks such as blood clots and infections. 

• Identifying the signs of deep vein thrombosis (DVT) and pulmonary embolism. 

• The risk of joint-specific complications like dislocation or leg length inequality. 

• Primary causes of surgical risks including pre-existing health conditions. 

• Common lifestyle triggers that can increase the likelihood of complications. 

• Differentiating between normal post-operative pain and ‘red flag’ symptoms. 

• The long-term risk of implant wear and the potential for revision surgery. 

Immediate Surgical Risks: Blood Clots and Infection 

The two most significant risks immediately following joint replacement are blood clots and infection. Deep vein thrombosis (DVT) is a condition where a clot forms in the leg veins due to reduced mobility and changes in blood flow during surgery. If a part of this clot breaks off and travels to the lungs, it causes a pulmonary embolism (PE), which is a medical emergency. To mitigate this, UK hospitals provide blood-thinning medications (anticoagulants) and compression stockings, and encourage patients to walk within hours of the operation. 

Infection is another serious concern, occurring in approximately 1 in 100 cases. It can affect the skin around the incision or, more seriously, develop deep within the new joint. Surgeons use sterile operating environments (laminar flow theatres) and provide prophylactic antibiotics to reduce this risk. While minor surface infections can be treated with oral antibiotics, a deep infection may require further surgery to wash out the joint or, in rare cases, replace the implant. 

Joint-Specific Complications: Dislocation and Nerve Damage 

Beyond general surgical risks, there are complications specific to the joint being replaced. In hip replacements, there is a small risk of dislocation, where the artificial ‘ball’ pops out of the ‘socket.’ This is most common in the first six to twelve weeks while the surrounding soft tissues are healing. Patients are given specific ‘hip precautions’, such as not crossing their legs or bending past ninety degrees, to minimise this risk during the early recovery phase. 

Nerve and blood vessel damage are rare but possible during the surgical approach. In some cases, the nerves near the joint can be stretched or bruised, leading to temporary or, very rarely, permanent numbness or weakness in the limb. Additionally, in hip replacements, there is a risk of a slight leg length inequality. While surgeons aim for perfect symmetry, sometimes the joint must be tensioned in a way that makes one leg feel slightly longer than the other, though this often resolves as the patient regains muscle strength and adapts to their new gait. 

The Underlying Causes of Surgical Risk 

The likelihood of experiencing a complication is often linked to a patient’s overall health and the complexity of their joint wear. While the surgical team controls the environment within the hospital, pre-existing biological factors dictate how a person’s body responds to the stress of surgery and the presence of an artificial implant. 

Key clinical causes and risk factors include: 

• Pre-existing Health Conditions: Poorly managed diabetes, heart disease, or chronic kidney disease can interfere with healing and increase the risk of infection. 

• Obesity: A high Body Mass Index (BMI) places more stress on the surgical wound and makes the operation technically more challenging, increasing the risk of both infection and blood clots. 

• Smoking: Nicotine constricts blood vessels and significantly impairs the body’s ability to heal bone and skin, leading to a much higher rate of complications. 

• Previous Joint Surgery: If you are having a ‘revision’ or have had previous operations on that joint, the presence of scar tissue can increase the surgical difficulty. 

Environmental and Lifestyle Triggers for Complications 

A patient’s actions during the first few months at home can influence whether a potential risk becomes a clinical reality. Identifying and avoiding these lifestyle triggers is an essential part of the recovery process. Following the advice of your physiotherapist and surgical team is the most effective way to protect your new joint while it is in its most vulnerable state. 

Common triggers for post-operative complications include: 

• Sudden High-Impact Activity: Attempting to run or lift heavy objects too soon can cause the implant to shift or lead to a fracture around the prosthesis. 

• Poor Wound Hygiene: Touching the incision with unwashed hands or exposing it to dirty water before it has fully healed. 

• Sedentary Behaviour: Staying in bed for long periods increases the risk of blood clots; ‘pacing’ should involve frequent, short walks rather than total rest. 

• Ignoring Hip Precautions: Bending too far or twisting the leg excessively before the joint capsule has tightened. 

• Poor Nutrition: A diet lacking in protein and vitamins can slow down tissue repair and weaken the immune system. 

Differentiation: Normal Recovery vs Red Flag Symptoms 

It is essential to differentiate between the expected discomfort of major surgery and symptoms that indicate a serious complication. Some pain, swelling, and bruising are entirely normal and to be expected in the first few weeks. However, UK clinical guidelines highlight specific ‘red flag’ signs that require immediate medical attention to prevent long-term damage. 

Key differences include: 

• Normal Swelling: Usually localised to the joint, improves with elevation and ice, and gradually decreases over time. 

• Red Flag Swelling: A calf that is significantly more swollen, red, hot, and painful than the other side (a potential sign of DVT). 

• Normal Pain: A dull ache that is well-controlled by prescribed medication and worsens only with exercise. 

• Red Flag Pain: A sudden, excruciating increase in pain, or pain accompanied by a high fever and chills (potential signs of infection or dislocation). 

• Pulmonary Embolism Signs: Sudden shortness of breath, chest pain when breathing in, or coughing up blood. 

Long-Term Risks: Wear and Loosening 

While most risks occur in the weeks following surgery, there are long-term considerations regarding the lifespan of the artificial joint. Over many years, the materials, typically plastic, metal, or ceramic, can wear down. This wear can produce microscopic particles that cause the body to reabsorb the bone around the implant, a process called ‘aseptic loosening.’ 

If an implant becomes loose, it can cause a return of the deep, dull ache the patient felt before their initial surgery. This may eventually necessitate a revision surgery, which is a more complex operation than the original replacement. Maintaining a healthy weight and avoiding high-impact sports are the best ways to minimise this long-term risk and ensure the replacement lasts as long as possible. Regular follow-up appointments, often involving an X-ray every few years, allow clinicians to monitor for these changes before they become symptomatic. 

Conclusion 

Joint replacement surgery is a safe and transformative procedure, but it involves inherent risks such as blood clots, infection, and joint-specific issues like dislocation. While the clinical success rate in the UK is very high, the effectiveness of the operation depends on a partnership between the surgical team’s skill and the patient’s commitment to a healthy recovery. By managing your health before surgery and diligently following post-operative instructions, you can significantly reduce these risks. Recognising ‘red flag’ symptoms early ensures that any complications are treated promptly, allowing you to return to an active and pain-free life. 

According to NHS guidance on joint replacement risks, most complications are rare and can be treated effectively if caught early. 

If you experience severe, sudden, or worsening symptoms, call 999 immediately. 

Authority Snapshot 

This article was written by Dr. Stefan Petrov, a UK-trained physician with an MBBS and postgraduate certifications including Basic Life Support (BLS), Advanced Cardiac Life Support (ACLS), and the UK Medical Licensing Assessment (PLAB 1 & 2). Dr. Petrov has extensive hands-on experience in general medicine, surgery, and emergency care, having worked in both hospital wards and intensive care units. He is dedicated to medical education and ensuring that patient-focused health content is accurate, safe, and aligned with UK clinical standards.