LCP, or Legg-Calvé-Perthes disease, is a childhood hip condition where the blood supply to the ball-shaped top of the thighbone (femoral head) is temporarily disrupted, causing the bone to weaken, collapse, and eventually regrow. It affects roughly 3 out of every 100,000 children between ages 2 and 12, and boys are significantly more likely to develop it than girls, with an incidence of 5.1 per 100,000 in boys compared to 0.42 per 100,000 in girls. The condition typically affects only one hip, though both can be involved at different times.
What Happens Inside the Hip
The femoral head sits at the top of the thighbone and fits into a socket in the pelvis, forming the hip joint. In LCP, something interrupts the blood flow to this ball of bone. Without a steady blood supply, the bone tissue dies and softens. The exact trigger for this blood supply disruption isn’t fully understood, but the result is predictable: the bone can no longer support the forces of walking and running, and it begins to break down.
What makes LCP different from many bone conditions is that the body actually repairs the damage on its own. New bone cells gradually replace the dead tissue over a period of years. The critical question is whether the femoral head keeps its round shape during that rebuilding process or becomes flattened and misshapen, which determines how well the hip functions long-term.
The Four Stages of the Disease
LCP progresses through four distinct phases visible on X-rays, each with a different timeline.
In the initial stage, the bone loses its blood supply and begins to harden and die. This phase lasts about 5 months on average but can range from 1 to 14 months. The fragmentation stage follows, lasting roughly 8 to 9 months, during which the body breaks down and absorbs the dead bone. The hip is most vulnerable to deformity during this period because the softened bone can collapse under pressure.
The reossification stage is the longest, averaging 19 months but potentially stretching past 4 years in some cases. New bone-forming cells move in and rebuild the femoral head. Finally, in the residual or remodeling stage, the new bone matures and reshapes itself as the child grows. From start to finish, children who respond well to conservative treatment typically heal within 2 to 4 years.
Symptoms to Recognize
The most common early sign is a limp that develops gradually, sometimes without any obvious injury. Children often complain of pain or stiffness in the hip, groin, thigh, or knee. The knee pain can be misleading, since parents and even some clinicians may not immediately connect it to a hip problem.
Pain tends to worsen with activity and improve with rest. Over time, the hip joint loses some of its range of motion, making it harder for the child to move the leg outward or rotate it normally. Because the onset is gradual, some children limp for weeks before anyone suspects a bone problem rather than a muscle strain.
How LCP Is Treated Without Surgery
The primary goal of treatment is “containment,” keeping the femoral head seated deeply within the hip socket so it maintains a round shape as it rebuilds. A well-contained femoral head uses the socket like a mold, preventing the bone from flattening as new tissue forms.
For many children, especially those diagnosed before age 6, conservative treatment is sufficient. This can include rest, anti-inflammatory medications for pain, physical therapy to maintain hip flexibility, and in some cases bracing or casting. Older-style rigid braces and long-term casts have largely fallen out of favor because they were physically and psychologically difficult for children to tolerate. Modern approaches lean toward more functional braces worn for shorter periods, combined with targeted exercises to prevent the muscles around the hip from tightening.
A key part of non-surgical care is preventing contractures, where the muscles around the hip shorten and stiffen. Gentle stretching and, in some cases, intermittent manual traction help keep the muscles at their proper length while reducing pressure inside the joint.
When Surgery Is Needed
Surgery is typically considered for older children or those whose femoral head is protruding out of the hip socket despite conservative care. The most common procedure is an osteotomy, where the surgeon cuts and repositions either the thighbone or the pelvic bone to better cover the femoral head and improve containment.
The best results come from operating early in the disease process, before significant collapse has occurred. In later stages, osteotomy can still be performed as a salvage procedure for hips that are painful and deformed, as long as passive range of motion remains. For children under age 4, surgeons often take a wait-and-see approach because younger children tend to have better natural remodeling potential.
Activity During Recovery
Activity restrictions vary by stage but follow a consistent pattern. During the initial and fragmentation stages, when the bone is most vulnerable, high-impact activities like trampolining, running, ball sports, and gymnastics are typically discouraged. Low-impact activities are generally allowed and even encouraged: swimming, short walks, cycling, and horseback riding are considered safe throughout all stages of the disease.
As the child enters the reossification stage, restrictions gradually loosen. Cross-country skiing and skating may be added to the approved list. Opinions among orthopedic specialists become less unanimous at this point, reflecting the reality that each child’s bone healing progresses differently. The transition back to full activity is individualized, guided by X-ray evidence of bone recovery and the child’s comfort level.
Long-Term Outlook
The final shape of the rebuilt femoral head determines long-term hip health. A femoral head that remains round and fits well in the socket can function normally for decades. A flattened or enlarged femoral head creates an uneven fit that accelerates wear on the joint cartilage, raising the risk of osteoarthritis earlier in adulthood.
Several factors influence outcome. Age at diagnosis is one of the strongest predictors: younger children have more growth remaining, which gives the femoral head more time to remodel into a functional shape. The extent of bone involvement matters too. Children with less than half the femoral head affected generally do better than those with more extensive damage. Gender plays a role as well, with girls tending to have somewhat worse outcomes despite being affected far less often, possibly because they mature skeletally earlier and have less remodeling time.
Many children with LCP go on to have fully active lives with no significant hip limitations. Those who do develop arthritis from residual deformity may eventually need a hip replacement, but this often doesn’t become necessary until middle age or later, giving them decades of functional use.