Total knee replacement surgery, also known as total knee arthroplasty (TKA), is one of the most commonly performed orthopaedic procedures in the world. In Australia alone, tens of thousands of these surgeries are carried out each year, predominantly in patients over the age of sixty suffering from severe osteoarthritis, rheumatoid arthritis, or traumatic joint damage. While the procedure is widely celebrated for restoring mobility and reducing chronic pain in the knee joint, its effects ripple throughout the entire lower limb. Among the most overlooked consequences of knee replacement surgery are the changes it brings to the feet — changes that are biomechanical, circulatory, neurological, and rehabilitative in nature. Understanding these effects is essential not only for patients preparing for surgery but also for the healthcare professionals guiding their recovery.
Biomechanical Changes and Altered Gait
The knee is the central hinge of the lower limb, and its alignment profoundly influences how force is transmitted to the foot during walking and standing. Many patients who arrive at surgery have spent years, or even decades, walking with a compromised gait pattern. Severe knee arthritis commonly causes either a varus deformity (bow-legged alignment) or a valgus deformity (knock-kneed alignment), both of which alter the mechanics of foot strike and weight distribution. During this prolonged period of compensatory movement, the foot adapts — sometimes developing structural changes such as overpronation, supination, or altered arch height in response to the uneven load placed upon it.
Following surgery, the corrected knee alignment creates a fundamentally new biomechanical environment. The foot, which had adapted to years of abnormal loading, must now readjust to a corrected joint axis. This realignment can cause unexpected discomfort in the foot, particularly in the arch, heel, and metatarsal region, as muscles, tendons, and ligaments that were conditioned for a different pattern of movement are asked to function differently. Plantar fasciitis, metatarsalgia, and heel pain are among the conditions that may emerge or worsen in the months following surgery as the body recalibrates its gait cycle.
Swelling, Circulation, and Oedema in the Feet
One of the most immediate and noticeable effects of knee replacement surgery on the feet is swelling. Post-operative oedema is an almost universal experience following TKA, and while swelling is centred around the knee, it frequently extends down the lower leg and into the ankle and foot. This occurs because the surgical trauma disrupts local lymphatic and venous drainage pathways, causing fluid to accumulate in the surrounding tissues. Gravity compounds the problem — when patients begin mobilising, fluid naturally pools in the most dependent regions of the limb, namely the ankle and foot.
This swelling can make footwear uncomfortable or difficult to fit, and in some cases contributes to pressure-related skin problems if not managed appropriately. Patients are often advised to elevate their legs and wear compression stockings in the early recovery period to encourage venous return. The risk of deep vein thrombosis (DVT) further complicates the circulatory picture: blood clots can form in the deep veins of the calf or thigh following surgery, and when they do, the foot may experience pain, warmth, and additional swelling. DVT is a serious post-operative complication that requires prompt medical attention, and its effects on the foot can sometimes be the first visible sign that something is wrong.
Nerve Function and Sensory Changes in the Foot
The nerves that supply sensation and motor control to the foot travel through and around the knee joint. During knee replacement surgery, the peroneal nerve — which branches near the lateral aspect of the knee — is particularly vulnerable to traction, compression, or inadvertent damage. The peroneal nerve supplies sensation to the dorsum of the foot and controls the muscles responsible for dorsiflexion and eversion. Injury to this nerve can result in a condition known as foot drop, where the patient is unable to lift the front part of the foot when walking, causing the toes to drag along the ground. While full peroneal nerve injury is relatively uncommon in TKA, transient neuropraxia — a temporary disruption in nerve conduction — is more frequently reported.
Patients may also experience tingling, numbness, or altered sensation in the foot following surgery, particularly along the inner ankle or the sole. These sensory changes are often temporary and resolve as swelling subsides and the nerve recovers, but in some cases they persist for months. For patients who already have conditions such as peripheral neuropathy or diabetes, the nerve-related effects of knee surgery on the feet require particularly careful monitoring, as their baseline sensory function may already be compromised.
Rehabilitation, Footwear, and Podiatric Care
Rehabilitation following total knee replacement is a gradual and carefully structured process, and the role of the foot in this recovery is significant. Physiotherapists work to restore the normal gait cycle, but this process demands that the foot functions correctly as the base of support. If foot pain, weakness, or stiffness interferes with rehabilitation exercises, the recovery of the knee itself can be delayed. Early weight-bearing exercises, which are encouraged almost immediately after surgery, place considerable demand on the foot — requiring both plantar sensation for proprioceptive feedback and adequate strength in the intrinsic and extrinsic foot muscles.
Footwear choices during the recovery period are more important than many patients realise. Supportive, well-fitted shoes with adequate cushioning and a stable heel counter help to absorb impact forces that the recovering knee is not yet able to manage efficiently. Inappropriate footwear — such as loose slippers or flat, unsupportive sandals — can not only increase the risk of falls but may also place undue stress on the foot and ankle, leading to secondary musculoskeletal complaints. In cases where pre-existing foot deformities such as hallux valgus, flat feet, or high arches are present, custom orthotics prescribed by a podiatrist can significantly improve comfort and gait mechanics during rehabilitation.
Long-Term Implications for Foot Health
In the long term, a successful knee replacement can actually benefit foot health by resolving the chronic compensatory patterns that were damaging the foot over years of abnormal loading. Patients who previously walked with a pronounced limp or antalgic gait may find that, once rehabilitated, their feet are subjected to more even and appropriate forces than they have experienced in years. Conditions such as stress fractures, callus formation, and deformity progression that were driven by maladaptive gait may stabilise or improve.
However, outcomes are not universally positive. Some patients continue to experience residual foot and ankle symptoms even after a technically successful knee replacement, highlighting the importance of a whole-limb approach to assessment and treatment. Orthopaedic surgeons, physiotherapists, and podiatrists working collaboratively can address this complexity more effectively than any single clinician working in isolation.
Knee replacement surgery is a transformative intervention that can restore quality of life for those suffering from debilitating joint disease. Yet its effects extend well beyond the knee, with the feet serving as both a recipient of post-operative changes and a critical participant in recovery. From the altered biomechanics of a corrected joint, to the swelling that pools in the ankle, the nerve changes that affect sensation, and the rehabilitation demands that require foot strength and stability — the feet are intimately involved in every stage of the knee replacement journey. Giving proper clinical attention to foot health before, during, and after surgery is not merely ancillary care; it is an essential component of comprehensive, patient-centred orthopaedic management.