Pain in the knee does not always start in the knee. Sometimes the real source of the problem is higher up in the body, especially in the hip. One muscle that often gets overlooked is the iliopsoas. Iliopsoas muscle spasm or injury usually causes groin or front-of-the-hip pain, but it can also lead to knee pain. This happens through referred pain patterns or irritation of nearby nerves, not because the muscle directly connects to the knee. Understanding this relationship can help people get the right diagnosis and treatment instead of focusing only on the knee.
The iliopsoas is a deep muscle made up of two parts, the psoas major and the iliacus. These muscles join together and attach to the top of the thigh bone. The iliopsoas is the main muscle used to lift the knee toward the chest and plays a big role in walking, running, climbing stairs, and getting up from a chair. It also helps stabilize the spine and pelvis and supports balance during movement. Because of its deep location and important role, problems with the iliopsoas can affect many areas of the body.
One reason iliopsoas problems can cause knee pain is its close relationship with the femoral nerve. The femoral nerve runs right next to the iliopsoas muscle as it travels from the lower back into the thigh. This nerve controls the muscles that straighten the knee and provides feeling to the front of the thigh and knee. If the iliopsoas becomes swollen, tight, or injured, it can press on the femoral nerve. When this happens, pain, weakness, or numbness can be felt in the thigh or knee, even though the knee itself is not injured.
Knee pain linked to the iliopsoas can also occur without nerve compression. This happens through referred pain, where the brain interprets pain signals as coming from a different area than the true source. Because the iliopsoas shares nerve pathways with parts of the thigh and knee, irritation in the muscle can be felt lower down the leg. This type of pain is usually dull, aching, and hard to pinpoint, which can make diagnosis challenging.
The iliopsoas also affects knee pain in a more indirect way by changing how the hip and leg move. Tightness or spasm in the iliopsoas can tilt the pelvis forward and change the position of the thigh bone. These changes can affect how forces travel through the leg during walking, running, or squatting. Over time, this altered movement can increase stress on the kneecap, leading to patellofemoral pain and problems with patellar tracking, where the kneecap does not glide smoothly in its groove.
Patellofemoral pain is one of the most common causes of knee pain, especially in active people. It is often linked to muscle imbalances rather than a single injury. Weak hip muscles, tight thigh muscles, and poor movement control all play a role. Iliopsoas tightness is one of the muscle issues commonly seen in people with patellofemoral pain. When the iliopsoas is too tight, it can encourage inward rotation of the thigh and collapse of the knee during movement. This puts extra pressure on the kneecap and can worsen pain.
Studies have shown that people with patellofemoral pain often have a positive Thomas test, which indicates iliopsoas tightness. Treatment programs that improve iliopsoas flexibility and hip strength are linked with better outcomes. In fact, patients who regained normal iliopsoas length and improved hip strength were much more likely to report successful pain relief. This supports the idea that treating the hip, not just the knee, is essential for long-term improvement.
Because the connection between the iliopsoas and knee pain is indirect, careful evaluation is needed. Knee pain has many possible causes, including arthritis, ligament injuries, meniscus tears, nerve problems from the spine, and circulation issues. Iliopsoas-related knee pain can look similar to lumbar radiculopathy, where a nerve in the lower back is irritated, or to primary knee conditions. A detailed history and physical exam are key to telling these conditions apart.
During the exam, clinicians often check resisted seated hip flexion, which activates the iliopsoas. Pain or weakness during this test may point toward iliopsoas involvement. Palpation of the muscle, though sometimes uncomfortable, can also reproduce symptoms. Special tests like the Thomas test help assess muscle tightness. Because iliopsoas problems often occur alongside hip joint issues, imaging of the hip is usually more helpful than imaging of the knee when this condition is suspected.
Treatment for iliopsoas-related knee pain usually starts with conservative care. Physical therapy is the foundation and focuses on improving hip flexibility, strengthening weak muscles, and correcting movement patterns. Stretching the iliopsoas, strengthening the gluteal and core muscles, and improving control during walking and squatting are key goals. High-repetition, low-load exercises for the hips and thighs have been shown to reduce knee pain and improve function over time.
Other treatments may be added depending on the case. Activity modification, short-term use of anti-inflammatory medications, or targeted injections may help reduce pain and allow therapy to be more effective. Some therapists use dry needling to treat trigger points in hip muscles, including the iliopsoas. Research suggests dry needling may provide short-term pain relief when combined with exercise, but it should not replace a structured strengthening program.
Overall, iliopsoas muscle spasm or pathology can contribute to knee pain through nerve irritation, referred pain, and altered movement patterns. The relationship is real but indirect, which is why it is often missed. When knee pain does not improve with standard treatments, looking higher up the chain at the hip and pelvis is essential. Addressing iliopsoas function as part of a whole-body approach can lead to better outcomes, less pain, and a faster return to normal activity.
