How is the hip structured?
The hip joint is formed by the head of the femur and a deep socket in the pelvis called the acetabulum. The joint surfaces are covered by cartilage, and around the edge is the labrum that deepens the socket.
A strong joint capsule and several ligaments provide stability. Muscles around the buttocks, thighs, and pelvis control movement and keep the pelvis stable when you walk or stand on one leg.
The hip is deep, which means that the location of the pain does not always correspond to the structure that is affected. Back pain can radiate to the hip and leg.
What function does the hip have?
The hip joint can flex, extend, rotate, and adduct. It transfers body weight from the pelvis to the legs and is exposed to great forces when walking, running, and jumping.
The hip muscles stabilize the pelvis and control the position of the leg. Reduced strength can affect the knees and back. Joint cartilage and synovial fluid reduce friction, while the labrum and joint capsule contribute to stability.
Good function depends on the combination of mobility, muscle control and gradual adaptation to load.
The hip is affected by how the pelvis is kept stable when the body weight is transferred from one leg to the other. Weakness in the gluteal muscles can compensate in the pelvis, knees and lower back, but is rarely the only cause of pain.
Common hip problems
Osteoarthritis can cause gradually increasing pain and stiffness, often in the groin. Tendon problems and irritation in the bursa often cause pain on the outside of the hip. Labral injuries, stress fractures, and bone marrow involvement are other possible causes.
Pain in the buttocks or back of the thigh can come from the lower back or nerve damage. Read more about hip pain, hip pain and osteoarthritis of the hip.
After a fall, a hip fracture can cause severe pain and inability to bear weight. In some people, the pain may be less pronounced despite the fracture.
The location of the pain provides guidance: groin and front of thigh more often indicate a joint, outside for tendons or bursae, and buttock or back for back, muscle or nerve involvement. The pattern is not absolute and needs to be tested clinically.
When should you seek care for your hip?
Contact your healthcare provider if the pain is persistent, affects walking or sleeping, or if mobility gradually decreases. Assessment is also needed if there are recurring locking, clicking with pain, or obvious weakness.
Seek emergency care if you are unable to stand or put weight on your leg after a fall, if the leg looks shortened or externally rotated, or if the pain is very severe. A red, warm, and swollen hip area with a fever needs prompt evaluation.
Sudden weakness or numbness in the leg may be due to nerve damage and should be assessed based on other symptoms.
How is the hip examined?
The doctor or physiotherapist assesses gait, mobility, strength, tenderness and whether the pain seems to come from the hip joint, tendons, bursae or back. The location of the pain and what movements provoke it are important clues.
X-rays are common when osteoarthritis or fractures are suspected. Ultrasound can show superficial tendons, bursae, and fluid. MRI provides detailed images of cartilage, labrum, bone marrow, tendons, and muscles.
In the case of an acute suspected fracture, CT or MRI may be used if the X-ray is normal but the symptoms still indicate an injury.
Sometimes a diagnostic injection into the hip joint is used to assess whether the pain is truly coming from the joint. This can be valuable when both the hip and lower back show changes and the symptom picture is difficult to delineate.
When can MRI of the hip be relevant?
MRI hip may be relevant in cases of suspected labral injury, stress fracture, bone marrow involvement, tendon or muscle injury, unexplained long-term pain or when X-rays do not explain the symptoms.
MRI is not always necessary in typical osteoarthritis, where clinical assessment and X-rays are often sufficient. The images can also show changes that do not cause symptoms.
The choice of examination area is important. Pain that actually comes from the lower back requires a different assessment than pain from the hip joint itself.
Limitations and next steps
Hip pain is often treated with load adjustment, strength and mobility training, and pain relief. An MRI finding alone does not determine whether surgery is needed.
The next step may be physiotherapy, injection treatment, orthopedic assessment or treatment of back-related nerve damage. In case of deterioration or new inability to bear weight, a new assessment should be made.
In osteoarthritis, exercise, weight adjustment and pain relief can be effective before surgery is considered. In tendon problems, gradual loading is often needed over a longer period of time. Rapid changes in exercise intensity or total rest can both make recovery more difficult.