Patients with cam impingement have typical hip joint-type symptoms [3]. The onset may be gradual or associated with an acute episode, which is the culmination of altered wear developing over a protracted period of time. Patients with cam impingement usually have reduced joint motion which can result in other secondary disorders. Athletes compensate with increased pelvic motion, often resulting in problems with athletic pubalgia [4]. More stress is placed on the lumbar spine, resulting in concomitant lumbar disease.

Pain with flexion, adduction, and internal rotation is almost uniformly present and is referred to as the “impingement test” (Fig. 2) [5]. However, in this author’s experience, this maneuver is uncomfortable for most irritable hips, regardless of the underlying etiology, and thus is not specific for impingement. Laterally based cam lesions may result in painful abduction or external rotation (Fig. 3). Internal rotation of the flexed hip is usually diminished but may be preserved in some patients (Fig. 4). Limited range of motion may be present bilaterally as the morphological variation is often present in both hips.

Radiographs are essential to the routine evaluation of impingement. A well-centered AP pelvis X-ray is important for assessing the acetabular indices of pincer impingement but also allows observations on the cam lesion by comparing both hips (Fig. 5) [6]. The epicenter and shape of the cam lesion are variable. Thus, while the 40° Dunn view has been reported as the best image, in this author’s experience, no single lateral radiographic view is reliable for optimally assessing the cam lesion in all cases (Fig. 6) [7]. Sometimes the cam lesion is more anteriorly based and sometimes more lateral. The characteristic feature is loss of sphericity of the femoral head. The alpha angle has been described to quantitate this observation (Fig. 7) [8]. However, imaging will under interpret this measurement unless it catches the maximal location of the cam lesion. No studies have shown a significant correlation between the amount of alpha angle correction and the results of surgery, indicating that there may be other factors at play; but higher alpha angles have been associated with more clinically relevant lesions [9, 10].

Magnetic resonance imaging (MRI) and gadolinium arthrography with MRI (MRA) aid in assessing secondary damage to the articular cartilage and labrum associated with cam impingement [11]. These studies are better at detecting labral pathology and less often reveal the severity of articular involvement. Alpha angle can again be recorded but is still variable depending on whether the cross-sectional images catch the maximal location of the cam lesion.

Computed tomography with 3-D reconstruction provides great clarity in evaluating the shape, size, and location of the cam lesion. This is quite valuable for the arthroscopic management of this condition. Exposure of the abnormal bone is simplified by knowing its exact appearance.

The indication for hip arthroscopy is imaging evidence of intra-articular pathology amenable to arthroscopic intervention, or sometimes simply recalcitrant hip pain that remains refractory to efforts at conservative treatment, keeping in mind that imaging studies may often underestimate the severity of intra-articular pathology. Correction of the cam lesion is performed, especially when there is arthroscopic evidence that it is responsible for the concomitant joint pathology. This secondary joint damage is best characterized by failure of the anterolateral acetabular articular surface. The failure is most typically represented by articular delamination with the peel-back phenomenon but, earlier in the disease process, may be characterized by simply deep closed Grade I articular blistering, referred to as the wave sign [12].

It is this author’s opinion that simply radiographic findings of impingement, in the absence of clinical findings of a joint problem, are not an indication for arthroscopy. Some individuals with impingement morphology may function for decades without developing secondary joint damage and symptoms. For some it is unclear when, or if, they will develop problems warranting surgical intervention. For example, many individuals may present with symptoms in one hip when radiographic findings of impingement are present in both. While intervention in the asymptomatic joint would not be appropriate, it is important to educate the patient about warning signs of progressive joint damage. It is a clinical challenge in the decision not to intercede too early or too late. In this author’s experience, 93 % of patients undergoing arthroscopy for cam impingement demonstrate Grade III and Grade IV articular damage, reflecting that the disease process is already substantially advanced at the time of intervention [1].

Objective contraindications include advanced disease states characterized by Grade 3 Tonnis changes, or less than 2 mm remaining joint space [13–15]. Prominent cam lesions, almost by definition, constitute a Grade 2 Tonnis change and broad spectrum of disease. Larson has subcategorized Tonnis 2 into those with greater or less than 50 % joint space remaining, showing poorer results among those with less than 50 % residual space [15]. Subjective contraindications may include the patient’s expectations of surgery. If the patient has unreasonable goals of what the procedure may accomplish, then surgery may not be the best option. Also, in the presence of secondary degenerative disease, the potential advantages of a joint preserving procedure must be weighed against the high level of satisfaction associated with joint arthroplasty.