Cam impingement is a hip condition where the ball of the hip joint isn’t perfectly round. Instead, it has a bump or extra bone at the junction where the ball meets the neck of the thighbone. This irregular shape prevents the ball from rotating smoothly inside the socket, and over time, it grinds against the cartilage lining the socket. The result is hip pain, stiffness, and if left unaddressed, a significantly higher risk of developing hip arthritis.
The full medical name is cam-type femoroacetabular impingement (FAI), meaning the thighbone (femur) and hip socket (acetabulum) aren’t fitting together the way they should. It’s one of the most common structural causes of hip pain in younger, active adults.
What’s Different About the Hip Joint
In a healthy hip, the top of your thighbone is shaped like a smooth sphere that sits snugly inside a deep cup in your pelvis. This ball-and-socket design allows your leg to move freely in all directions. With cam impingement, the ball has a bump or ridge along its edge, almost like a slight oval shape where there should be a perfect curve.
When you bend your hip, especially during deep flexion or twisting inward, that bump gets jammed into the rim of the socket. Each time this happens, the bony ridge shears against the cartilage lining the inside of the socket. Research consistently shows that cam deformity primarily damages this articular cartilage rather than the labrum (the rubbery gasket around the socket’s rim), which often stays intact early on. The bump also disrupts the thin layer of fluid that normally cushions the joint during movement, accelerating wear.
This bone shape typically develops during adolescence, when the hip is still growing. Physical activity during the teenage years, particularly high-impact sports, appears to play a meaningful role in whether a cam bump forms. Interestingly, cam morphology is extremely common even in people with no symptoms. A study of young soccer players found cam-type changes on MRI in nearly 78% of hips, and a large systematic review found it in 37 to 55% of athletes and about 23% of the general population. Having the shape doesn’t guarantee you’ll have problems, but it does set the stage.
How Cam Impingement Feels
The hallmark symptom is a deep ache in the groin or inner hip. People often notice it after sitting for a long time, like during a car ride, or after activities involving repeated hip bending such as squatting, climbing stairs, or running. Many describe the pain by cupping their hand over the front of the hip in a “C” shape.
Other common symptoms include:
- Clicking, catching, or locking in the hip joint
- Stiffness that makes it hard to put on socks or tie shoes
- Pain walking uphill or during any activity requiring deep hip flexion
- Low back pain, because restricted hip movement forces the spine and pelvis to compensate
- Pain at the side of the hip or buttock, which can mislead people into thinking the problem is elsewhere
Symptoms tend to come on gradually. Many people tolerate mild discomfort for months or years before it becomes persistent enough to seek help. The pain is typically activity-related early on, but it can progress to bothering you at rest if cartilage damage advances.
How It’s Diagnosed
Diagnosis starts with a physical exam. The most widely used clinical test is the FADIR test: your doctor bends your hip up toward your chest, angles your knee inward, and rotates the thighbone inward. If this reproduces your familiar groin pain, it’s a strong clue. The FADIR test picks up about 80% of true cases, making it a good screening tool, though it can also be positive with other hip problems, so it’s never used alone.
Imaging confirms the diagnosis. Standard X-rays can reveal the bony bump on the femoral head, and doctors measure something called the alpha angle, which quantifies how far the bone shape deviates from round. An alpha angle of 60 degrees or more is the current threshold for classifying cam morphology. MRI provides more detail about cartilage and labral health, which helps guide treatment decisions. It’s worth noting that the alpha angle is a classification tool, not a standalone diagnosis. Plenty of people with an angle above 60 degrees have no symptoms at all.
The Link to Hip Arthritis
This is probably the most important thing to understand about cam impingement. A 10-year study found that people with cam morphology had roughly 3 times the odds of developing hip arthritis compared to those without it. For larger cam bumps, those odds jumped even higher. When researchers looked specifically at end-stage arthritis (the kind that leads to hip replacement), cam morphology increased the odds anywhere from 5 to nearly 13 times.
That doesn’t mean everyone with a cam bump will need a hip replacement. But it does mean the condition is worth taking seriously, especially if you’re young and active. Early management, whether conservative or surgical, aims to slow or prevent that cartilage breakdown.
Conservative Treatment
Not everyone with cam impingement needs surgery. If your symptoms are mild to moderate, a structured physical therapy program is the typical first step. The goal is to strengthen the muscles around the hip so they better support the joint and reduce the mechanical stress on the cartilage.
Rehabilitation focuses heavily on the hip abductors (the muscles on the outside of your hip) and hip flexors. Common exercises include clamshells, bridges, lateral band walks, step-ups, and lunges. A typical program progresses through phases over several weeks, starting with gentle strengthening and gradually advancing to sport-specific movements. The benchmark for returning to running is usually achieving at least 90% of normal hip abductor strength.
Activity modification matters too. You’ll want to avoid positions and exercises that repeatedly jam the hip into deep flexion or internal rotation, since that’s exactly the motion that drives the bump into the cartilage. This might mean adjusting your squat depth, changing your cycling setup, or temporarily scaling back high-impact training. Anti-inflammatory strategies like icing after activity and short courses of over-the-counter pain relievers can help manage flare-ups.
When Surgery Is Considered
If conservative treatment doesn’t provide enough relief after several months, or if imaging shows significant cartilage damage, surgery becomes a reasonable option. The standard procedure is hip arthroscopy, a minimally invasive approach using small incisions and a camera.
The core of the surgery is a femoroplasty, which means reshaving the bump on the femoral head to restore a rounder shape. The surgeon first inspects the inside of the joint to assess cartilage and labral damage, then carefully removes the excess bone along with the fibrous tissue covering it. The goal is to eliminate the mechanical conflict so the ball can rotate freely in the socket again without grinding. If the labrum is torn, it can often be repaired during the same procedure.
Recovery After Surgery
Recovery from hip arthroscopy for cam impingement follows a phased rehabilitation program. You’ll typically use crutches for the first few weeks and gradually progress through range-of-motion exercises, then strengthening, then sport-specific training. Most people return to their sport or full activity at around 7 months on average, though the range is wide, from as early as 3 months to as long as 14 months depending on the extent of the surgery and the demands of the activity.
One thing to be aware of: even after completing formal rehab, studies show that dynamic hip strength can still be measurably lower than in people who never had the condition. This is why a thorough, progressive rehabilitation program matters more than simply watching the calendar. Returning to activity based on actual strength and movement quality, rather than a fixed timeline, produces better long-term results.