Limited range of motion (LROM) in the hip describes the difficulty or inability to move the leg through its full, normal arc of movement. The hip is a ball-and-socket joint, designed for extensive mobility to support movements like walking and bending. When motion becomes restricted, it signals an underlying physical mechanism that is impeding the smooth gliding of the joint surfaces. These restrictions can stem from issues within the joint, such as damage to the cushioning cartilage, or from problems in the surrounding bone structure and soft tissues.
Causes Related to Cartilage Breakdown
Limited hip movement often results from degenerative processes that destroy articular cartilage, the joint’s protective lining. Osteoarthritis (OA) is the most common cause, leading to the gradual wearing away of this smooth, shock-absorbing tissue. As the cartilage disappears, the joint space between the femoral head (ball) and the acetabulum (socket) narrows, causing bones to rub against each other.
The body attempts to stabilize the damaged joint by forming abnormal bony growths called osteophytes, or bone spurs, along the joint margins. These osteophytes physically block the joint from completing its full range of motion, creating a mechanical barrier that restricts movement like hip flexion or rotation. Rheumatoid Arthritis (RA) is another cause of cartilage destruction, an autoimmune condition where the immune system attacks the joint lining, leading to inflammation and cartilage loss. Both OA and RA result in a rough, uneven joint surface that causes pain and stiffness, particularly after periods of rest.
Structural Limitations of the Hip Joint
Mechanical restriction can also arise from an abnormal fit between the ball and socket, a condition known as Femoroacetabular Impingement (FAI). FAI occurs when the bone structure causes premature, abnormal contact between the femur and the acetabulum during movement. This collision causes microtrauma and leads to decreased range of motion, especially in movements that combine hip flexion and internal rotation.
There are two primary forms of FAI: CAM and Pincer impingement.
CAM Impingement
CAM impingement involves an excess bony prominence on the femoral head-neck junction, making the ball less spherical and causing it to jam into the socket.
Pincer Impingement
Pincer impingement is caused by an overgrowth of bone on the rim of the acetabulum, which creates excessive coverage over the femoral head.
The repetitive friction caused by FAI often damages the labrum, a ring of fibrocartilage that deepens the hip socket. A labral tear can lead to a sensation of catching or locking, further impeding smooth motion.
Soft Tissue Inflammation and Restriction
Restriction of hip movement can be caused by inflammation or tightness in the soft tissues surrounding the joint, not just internal joint problems. Hip bursitis, most commonly trochanteric bursitis, involves the inflammation of a fluid-filled sac (bursa) located over the prominent bony part of the outer hip. When this bursa becomes irritated, the resulting swelling and pain can make it difficult to move the hip comfortably, particularly with rotational movements.
Tendinitis, involving inflammation of the tendons around the hip, like the hip flexor or gluteal tendons, can also limit mobility. The pain from an inflamed tendon causes a protective tightening of the surrounding muscles, which restricts the joint’s ability to stretch and move fully. Severe contractures or tightness in major muscle groups, such as the psoas muscle or the piriformis muscle, can physically prevent the hip from achieving its full range. Acute muscle strains or tears in the hip or groin area similarly cause immediate restriction as the body locks down movement to protect the injured soft tissue.
When to Consult a Healthcare Provider
Any persistent or worsening limitation in hip motion warrants evaluation, particularly if it interferes with daily activities like walking or putting on shoes. Certain symptoms are red flags that require prompt attention, such as a sudden onset of severe pain or the complete inability to bear weight on the affected leg.
Medical consultation is appropriate when hip pain is accompanied by signs of systemic illness, such as fever or unexplained swelling that suggests a possible infection. An accurate diagnosis from a healthcare provider, often involving imaging studies like X-rays or MRI, is necessary to determine the specific mechanism causing the restriction. Seeking the input of an orthopedic physician or a physical therapist can ensure that the underlying cause is addressed with a targeted treatment plan.