Cam and Pincer Morphology on a Hip Scan

Two shapes, one on each side of the joint. The hip is a ball (the head of the thigh bone, or femur) in a socket (the acetabulum, part of the pelvis). Cam morphology is on the ball side: extra bone where the head meets the neck, so the head is not fully round. Pincer morphology is on the socket side: the rim reaches further over the ball than usual, all the way round or only at the front. A report that describes both calls it mixed.

Morphology, deformity, lesion. All three words describe the same shape. An international consensus panel agreed to use morphology, and to drop words with a negative ring such as lesion, abnormality and deformity (Dijkstra et al., 2022). Older reports and many studies still write cam deformity or cam lesion.

Impingement and the syndrome. Femoroacetabular impingement describes the ball and the rim of the socket meeting early in deep bending and turning. Femoroacetabular impingement syndrome is the diagnosis, and it needs three things together: symptoms that fit, signs on examination, and the shape on imaging (Griffin et al., 2016). A scan on its own cannot make it. The femoroacetabular impingement page covers the condition.

The words that come with it. These are the terms you are most likely to see with it on a hip or pelvis report.

These shapes are common in hips that do not hurt. A review pooled 26 studies of 2,114 hips with no symptoms, in people with an average age of 25. Cam morphology was reported in 37 percent, ranging from 7 to 100 percent between studies: about 55 percent in athletes and 23 percent in the general population. Pincer morphology was reported in 67 percent, with definitions that varied widely (Frank et al., 2015).

They are more marked, on average, in hips that do hurt. A review of 60 studies found cam morphology more often in people with symptoms and in athletes than in people without symptoms, and the average alpha angle was larger in the group with symptoms (Mascarenhas et al., 2016). The groups overlap, so a number on a report cannot sort one person into painful or not.

Cam morphology usually forms during growth. In 63 youth soccer players aged 12 to 19 who were X-rayed twice, about two and a half years apart, cam morphology developed gradually while the growth plate at the top of the thigh bone was still open, with no significant increase after it closed (Agricola et al., 2014). The consensus panel calls this primary cam morphology, to separate it from a cam shape left by an earlier hip condition (Dijkstra et al., 2022). In an adult the shape has usually been there since the teenage years, including through the years the hip did not hurt.

The scan does not make the diagnosis. An international group of 37 experts concluded that both the examination and imaging have limited ability to diagnose hip-related pain on their own, so the whole picture is needed. They recommend a front-on pelvis X-ray and a side view of the head and neck of the thigh bone as the first imaging, with MRI or other imaging only when more detail is needed, for example when planning surgery (Reiman et al., 2020).

It does not decide the treatment. What decides the plan is where the pain is, what brings it on and what the examination shows. Deep groin pain with sitting, squatting, getting out of a car or turning on the leg points to the joint. Pain on the outside of the hip or in the buttock usually points elsewhere, even with cam or pincer morphology on the report.

Cam morphology raises the odds of hip osteoarthritis. In 4,438 people aged 55 and over with no hip osteoarthritis at the start, followed for about nine years, those with cam morphology had roughly twice the odds of developing it on X-ray (Saberi Hosnijeh et al., 2017). In a Dutch cohort of 1,002 people aged 45 to 65 with early symptoms of osteoarthritis, an alpha angle above 60 degrees went with 3.7 times the odds of end-stage osteoarthritis within five years, and an angle above 83 degrees with 9.7 times the odds (Agricola et al., 2013).

Most hips with cam morphology still did not get there. In that Dutch cohort, 2.76 percent of hips reached end-stage osteoarthritis within five years. The hips most at risk had a severe cam shape together with reduced inward rotation on examination: about half of those reached end-stage osteoarthritis (Agricola et al., 2013). Ten years on, hips that began with pain, limited rotation and cam morphology together had much higher odds of osteoarthritis than hips with none of the three, but only 21 of 1,386 hips started in that group (Agricola et al., 2024).

For pincer morphology the link is weaker. Pincer morphology did not raise the risk of osteoarthritis in the study of people aged 55 and over (Saberi Hosnijeh et al., 2017). In 18,935 hips followed for up to eight years, moderate pincer morphology was not linked with new osteoarthritis, and severe pincer morphology went with 1.5 times the odds; 1.9 percent of all the hips developed it (Riedstra et al., 2026).

What that means for one hip. These studies describe groups. They show that the shape is one risk factor among several, and that most hips with it did not develop severe arthritis in the years they were followed. Whether reshaping the bone lowers that risk has not been shown. In a trial that measured cartilage health on MRI a year after surgery or physiotherapist-led care, the two groups did not differ significantly (Hunter et al., 2021).

As the hip bends deeply and turns inward, the front of the neck of the thigh bone moves toward the front rim of the socket. With extra bone at the head and neck junction, or a rim that reaches further over the ball, the two can meet earlier in the movement (Nötzli et al., 2002). The labrum and the cartilage at the edge of the socket sit between them, which is why reports that mention cam or pincer morphology often mention the labrum as well.

That matches the usual triggers: low chairs and long drives, deep squats, getting in and out of a car, and cutting or pivoting in sport. The shape is the same on good days and bad days, so how much the hip is asked to do in those positions, and how irritable the joint is at the time, account for much of the variation. Sitting higher, breaking up long periods of sitting and keeping squats above the depth that pinches may ease symptoms while strength is built up.

The consensus statement lists three suitable treatments for femoroacetabular impingement syndrome: conservative care, rehabilitation, and arthroscopic or open surgery (Griffin et al., 2016). The trials below compare rehabilitation with arthroscopy. Morphology found on a scan of a hip that does not hurt is not a reason for either.

• Exercise-based rehabilitation. An international consensus recommends exercise-based treatment for hip-related pain, for at least three months, and recommends staying physically active, sport included. The same group notes that strong evidence for physiotherapist-led treatment is lacking and that the best type and amount of exercise are not established (Kemp et al., 2020).
• Arthroscopy compared with physiotherapist-led care, UK FASHIoN. In 348 adults, both groups improved over 12 months. On a 100-point scale of hip-related quality of life, scores rose from about 39 to 59 with arthroscopy and from about 36 to 50 with a personalised physiotherapy program. After adjustment, arthroscopy scored 6.8 points higher, just above the smallest difference the trial counted as important, which was 6.1 points (Griffin et al., 2018).
• Arthroscopy compared with physiotherapy, FAIT. In 222 adults aged 18 to 60, scores for everyday activities eight months after joining were 10 points higher, on a 100-point scale, with arthroscopy than with a physiotherapy program of up to eight sessions (Palmer et al., 2019).
• A trial with a different result. In 80 military patients there was no significant difference between surgery and physiotherapy at two years. Of the 40 assigned to physiotherapy, 28 went on to have surgery, and analysing by the treatment people received did not change the result (Mansell et al., 2018).
• Taken together. A pooled analysis of three trials found a benefit for arthroscopy over non-surgical care in quality of life and everyday activities, and no significant difference in sports function (Mok et al., 2021). People improved in both arms of these trials, the differences were modest on average, and none of the trials compared surgery with a sham operation. The choice is a shared one, made with a surgeon when surgery is being considered.
• How long to give rehabilitation. The consensus recommendation is at least three months of exercise-based treatment (Kemp et al., 2020). Trying rehabilitation first did not close off surgery in the trials: in the military trial most of the physiotherapy group later chose it (Mansell et al., 2018).

I start with where the pain is and what brings it on: deep groin pain with sitting, squatting, getting out of a car or turning on the leg points to the joint, while pain on the outside of the hip or in the buttock usually points elsewhere. I ask about sport and training through the teenage years, how long it has been going on and what it stops you doing.

On examination I measure hip range of motion, inward rotation in particular, and test the movements that pinch at the front of the hip. A test that bends the hip, brings it across the body and turns it inward is useful mainly when it does not hurt, which makes the joint a less likely source (Reiman et al., 2020). I test strength in the hip and trunk and screen the lower back and the sacroiliac joint, because they refer pain to the same area. Then I read the report alongside what I found.

The plan is usually strength for the hip and trunk, work on the movements that provoke the hip so you can do them without pinching, and changes to the loads that flare it, built up toward the sport or activity you want back. Hands-on treatment can help with pain and movement alongside that. The femoroacetabular impingement page sets out the stages in detail, and the labral tear or impingement comparison covers how the two overlap.

If the hip is not responding after a fair course, usually about three months, the next step is a surgical opinion through your family doctor or a sports medicine physician. I cannot order imaging; when imaging would change the plan, I flag it to your family doctor or a sports medicine physician and refer you.