Osteoarthritis (OA) is a common joint condition involving the breakdown of cartilage and underlying bone, leading to pain and stiffness. Knee OA is one of the most frequently diagnosed forms of this progressive disease. A common concern is whether knee OA can cause pain in the adjacent hip joint. The answer is yes, as the biomechanical connection between these two joints means dysfunction in one often affects the other.
How Knee Problems Alter Hip Function
The lower extremity functions as a kinetic chain, meaning movement in the knee is interconnected with the mechanics of the hip and ankle. When the knee becomes painful due to OA, the body attempts to lessen the load and discomfort, triggering compensatory movements. This reaction results in an altered walking pattern known as an antalgic gait, or limp.
The painful knee causes an individual to shorten the time spent standing on that leg, reducing stride length and overall walking speed. This shift in weight distribution minimizes the increased ground reaction forces passing through the damaged knee joint. These altered mechanics disrupt the normal pathway of force through the leg, placing abnormal stresses on the hip and pelvis.
The shift in loading directly overloads the muscles surrounding the hip, particularly the gluteal muscles that stabilize the pelvis during walking. These muscles must work harder and in an abnormal pattern to maintain balance and avoid collapsing toward the painful knee. This chronic, increased demand can lead to muscle fatigue, strain, and irritation of the tendons and bursae around the hip joint.
The resulting strain often manifests as pain in the hip region, even if the hip joint itself shows no signs of primary OA. Patients with knee OA often exhibit a reduced range of motion in the hip during gait, which further contributes to an unstable walking pattern. These secondary changes in joint mechanics increase the likelihood of developing hip issues over time due to repetitive, unnatural loading.
Differentiating Secondary Hip Pain from Primary Hip Disease
Determining if hip pain is secondary to knee OA or a separate condition (primary hip OA) is a central part of the diagnostic process. The location of the pain offers initial clues. Pain originating from the hip joint itself is typically felt deep in the groin or anterior thigh. In contrast, hip pain caused by compensatory movements from the knee is often described as being on the lateral side of the hip, the buttock, or radiating down the outer thigh.
A physical examination is highly informative for distinguishing the source of the discomfort. Clinicians specifically assess the range of motion (ROM) of the hip joint, focusing on internal rotation. A hip joint affected by primary OA typically shows significant limitation and pain when the leg is rotated inward.
Conversely, if the hip pain is secondary to knee compensation, the hip’s internal rotation ROM is often preserved or only mildly restricted. The clinician may perform tests like the Trendelenburg test, which assesses the strength of the gluteal stabilizing muscles. This test often reveals weakness on the side of the painful knee, supporting the theory of muscle strain from altered gait mechanics rather than joint degradation.
Imaging studies, particularly X-rays, confirm the degree of OA in both joints. The knee X-ray confirms the severity of the primary issue. The hip X-ray helps rule out significant joint space narrowing or bone spur formation indicative of primary hip OA. Radiographic findings do not always correlate perfectly with the patient’s level of pain.
Treatment Approaches Targeting the Knee
Since the hip pain is often a byproduct of knee dysfunction, treatment focuses primarily on managing the knee OA to relieve compensatory stress on the hip. Physical therapy (PT) is a highly effective, non-surgical intervention for both knee and hip OA symptoms. PT programs aim to correct altered walking patterns and strengthen the muscles that support the knee.
Strengthening the quadriceps and hip abductor muscles is a primary goal, as this improves knee stability and reduces the abnormal loading that strains the hip. Neuromuscular exercises are also implemented to improve movement quality and control, helping the patient relearn a more symmetrical gait. Structured exercise is more effective than passive treatments like ultrasound or massage alone.
Temporary use of assistive devices, such as a cane, provides immediate relief by reducing the load placed on the affected knee during walking. This reduction in force lessens the need for the body to compensate, instantly decreasing biomechanical stress on the hip. Weight management is also beneficial, as reducing overall body weight lowers the mechanical load on both the knee and the stressed hip joint.
Medications and injections manage the inflammation and pain originating in the knee joint. Nonsteroidal anti-inflammatory drugs (NSAIDs) or corticosteroid injections into the knee reduce the primary pain source. This enables a patient to walk with less of an antalgic gait. By effectively treating the knee, the secondary hip pain often subsides without requiring specific hip-focused interventions.