Many individuals suffering from knee pain often attribute the discomfort directly to the knee joint itself, whether it's while walking, climbing stairs, or even resting. However, according to leading orthopaedic surgeon Mr. Mazin Ibrahim from The Princess Grace Hospital in London, the actual source of the pain frequently originates much higher up the leg – specifically, in the hips. He notes that many patients presenting with knee pain discover their knees are perfectly fine, with the real culprit being advanced arthritis in their hips.

This surprising connection is known as referred pain, a phenomenon where the brain misinterprets nerve signals, causing pain to be felt in a location different from its true origin. Mr. Ibrahim explains that due to the intricate wiring of our nervous system, pain can radiate from the hip to the knee, but not the other way around. He humorously recounts telling patients that they walk in with knee pain and leave needing a hip replacement, highlighting the effectiveness of hip surgery in resolving such referred knee discomfort.

The most common reason for referred knee pain from the hip is osteoarthritis, a widespread condition affecting millions globally and a major cause of disability. In the UK, approximately 10 million people live with osteoarthritis, with 3.2 million affected in the hip and 5.4 million in the knee. This wear-and-tear form of arthritis occurs when the protective cartilage cushioning bones erodes, leading to stiffness, pain, and inflammation in the joint. Women are more susceptible than men, and factors like age, obesity, and previous joint injuries increase the risk.

For severe hip or knee arthritis, surgical interventions like replacements are often necessary. Annually, the NHS performs over 120,000 knee replacements and 110,000 hip replacements, primarily for end-stage arthritis. These operations boast a high success rate, with over 90 percent effectively restoring mobility and alleviating pain, and artificial joints typically lasting 15 to 20 years. Early treatment focuses on non-surgical approaches, including lifestyle modifications such as weight loss, low-impact exercise, pain-relief medication, and physiotherapy. Mr. Ibrahim emphasizes that regular exercise is crucial for maintaining general health, muscle strength, and integrity, thereby preventing many joint problems.

Beyond arthritis, other hidden causes of knee pain include weakness in the abductor muscles—a group comprising the gluteus maximus, medius, and minimus. These muscles are vital for the stability of the leg and pelvis. When they are weak, they can alter leg movement and rotation. Patients often report their knee buckling, but it is actually rotating inwards due to insufficient strength in the hip abductors, while the knee joint itself remains structurally sound.

Sedentary lifestyles are largely to blame for hip issues and abductor weakness. Many individuals spend prolonged periods sitting at desks or on sofas, opting for lifts instead of stairs, and failing to adequately challenge their lower-body muscles. Even achieving the recommended 7,000 steps daily might not suffice if the activity lacks intensity, such as power-walking up an incline. Abductor weakness is particularly prevalent among older adults, especially women with osteoarthritis, who, due to stiff hips, tend to move less, further exacerbating muscle weakness.

Another significant cause of perceived knee pain originating from the hip is Greater Trochanteric Pain Syndrome (GTPS), which involves inflammation of the muscles and tendons on the outer side of the hip. This condition can cause excruciating pain that radiates down the leg. Initial treatment for GTPS and abductor weakness typically involves physiotherapy to strengthen the gluteal muscles, combined with anti-inflammatory medications like ibuprofen, diclofenac, or naproxen. In some cases, a steroid injection may also be necessary.

Furthermore, rheumatoid arthritis, an autoimmune disease affecting around 450,000 Britons, can also cause joint pain. In this condition, the immune system mistakenly attacks the lining of joints, leading to inflammation, swelling, stiffness, and pain. It can impact various joints, including the hips, knees, wrists, and fingers, and may also trigger systemic symptoms like fatigue and fever. Treatment usually involves immune-suppressing medication and physiotherapy to protect joint function and preserve mobility.

As life expectancy continues to rise—with UK men living to approximately 78 and women to 82 on average—maintaining joint health has become increasingly important for a healthy and happy old age. Mr. Ibrahim stresses that preventing hip and knee problems doesn't demand intensive gym workouts; simple, regular movement can make a substantial difference. He highly recommends swimming, as it engages all body muscles without stressing the joints, and cycling, which is excellent for strengthening the hips and knees, particularly the gluteal and quadriceps muscles.

For those prone to hip weakness, Mr. Ibrahim suggests a simple home exercise called clamshells: lie on your side with heels together and knees bent, then raise the top knee while keeping feet touching, pause, and lower. Adding a resistance band around the thighs enhances its effectiveness. This exercise can also be performed sitting down, making it convenient for multitasking. The fundamental message, according to Mr. Ibrahim, is to remain active and move the joints. He concludes that strengthening the hips not only protects them but can also proactively prevent knee pain from even starting.