Showalter, C. (2019, September 5). Mounting Evidence Refutes Long Held Prescribed Intervention of the Concave/Convex Rule in both the Shoulder and the Knee. Retrieved from 

Abstracted by: Chris Morse, ATC, SPT, Missouri State University, Springfield, Missouri 

This article, written by Dr. Showalter, gave a clear and thorough background to the concave-convex rule. It focuses on the two joints that have been “most studied,” according to the author: the Tibiofemoral and the Glenohumeral joints. The research indicated the work of MacConnaill and Basmajian (1969) as the origins of the Kaltenborn method, which beget the convex-concave rule. The author states that the rule itself is directly refuted by the Open MRI study performed by Beaulieu et al (1999), which concluded that “During abduction and adduction and internal and external rotation maneuvers with active subject muscle contraction, the humeral head remained precisely centered on the glenoid fossa in all asymptomatic subjects.” Their conclusion that there is no inferior movement of the humeral head, as suggested by the convex-concave rule, which directly refutes it. Another study by Johnson et al (2007) was included. This study tested the effectiveness of a posterior mobilization vs an anterior mobilization on the patient’s external rotation. Their conclusion was that the posterior mobilization increased external rotation more than the anterior mobilization that the convex-concave rule suggests. The author concludes his evidence against the convex-concave rule in the glenohumeral joint with a systematic review conducted by Brandt, et al (2007). In this review it was concluded that “The indirect method using Kaltenborn‘s convex–concave rule, as applied to the glenohumeral joint, needs to be investigated appropriately by primary studies to determine its true validity.” 

The author shifts his focus to the tibiofemoral joint to refute the convex-concave rule. In doing so, he quotes a study by Pollard (2008) that included 43 patients with Knee OA. In the study, the patients in the intervention group received a mobilization technique that the author stated was “a posterior (Kaltenborn) … mobilization” and was found to have a greater statistically significance in pain reduction against the control group, as well as “improved patient perceived function.” Dr. Showalter concluded that this study implies that mobilization in the opposite direction that is advocated by the concave-convex rule is superior. Next, a prospective observational study by Scarvell et al (2008) was included. This study evaluated movement of the femur in 25 healthy adults, while kneeling on a wooden box leaning back as far as possible while movement was tracked through a CT scan and digital fluoroscopic radiography. Scarvell concluded that “Deep flexion requires femoral posterior translation and external rotation. These findings invite review of the concave-convex rule as it might apply to manual therapy of the knee”. 

Next he includes his take home points. Starting with: a thorough assessment of the patient is pertinent to guide treatment. Second, he states the Maitland techniques are effective at treating patients with adhesive capsulitis and impingement. A study by Kumar et al (2012) is quoted that specifically Maitland grades III and IV are the most effective management of idiopathic shoulder adhesive capsulitis. Next, the author talks about the implications for clinical practice. He states: “Based upon ALL the evidence we have presented, consider using Maitland Anteroposterior (AP) Mobilizations on your next patient with Shoulder Adhesive Capsulitis (AC), Shoulder Impingement or Knee OA.” His final take home point: mobilizing opposite to the concave-convex rule, you are practicing true evidence based practice. He states that he practices under what he considers “evidence informed practice” to allow for the evidence to inform clinical practice rather than dictate

 Personal Commentary: 

As a student of the Cyriax and Kaltenborn approaches, I have come to appreciate the concave-convex rule as an important arthrokinematic concept to understand when considering joint motion. Furthermore, I have adapted these principles into my clinical practice to incorporate a comprehensive treatment plan. Dr. Showalter states he has evidence that unequivocally refutes the validity of the concave-convex rule, and therefore makes the Maitland technique, which he practices and teaches, superior. I am not a current student of the Maitland approach, and I have the utmost respect for this very thorough school of thought on joint manual therapy. However to claim it is superior to all other manual therapy approaches with the evidence he presented in this article must not go unchallenged.

I want to believe what Dr. Showalter is trying to convey, is that the indirect method of joint mobilization, which utilizes the concave-convex rule as a starting point, is not the most effective way. Here, Dr. Kaltenborn actually agrees with him. He states “the glide test (direct method) is the preferred method” in determining the direction of joint gliding limitation and that the indirect method could be used to deduce the limitation “for joints with very small ranges of movement, when severe pain limits movement, or for novice practitioners not yet experienced enough to feel gliding movement with direct testing.” The most effective mobilization treatments are those that stretch shortened joint structures in the direction of the most restricted gliding.” (Kaltenborn et al 1989) 

In his reference to Beaulieu et al (1999), the fact that their MRI revealed no inferior movement of the humeral head actually works in favor of the concave-convex rule. If the humeral head is to stay perfectly centered in the glenoid fossa, then it is demonstrating the most efficient type of movement possible, and thus the articulating surface is, in fact, gliding inferiorly as the rule states it should. If the humeral head were to translate in any direction, it would be pathological, and if the capsule were the culprit of this altered arthrokinematics, then mobilization would be indicated as a treatment. Neumann’s (2012) editorial about the same subject gives mathematical evidence for the concave-convex rule. He states “consider [that] an adult-size humeral head with a circumference of 16 cm. A motion of 90° of GH joint abduction occurring purely due to a rolling motion (with no concurrent inferior slide at the articular surface) would theoretically cause the humeral head to roll upward on the glenoid about 4 cm. … that the studies showed that the humeral head only migrates 1 to 3 mm upward is in itself proof of the existence of a significant, concurrent inferior slide during GH joint abduction.” 

In the Johnson et al study, they concluded that a posterior mobilization is more effective at improving external rotation in subjects with adhesive capsulitis. Since the patients in this study had adhesive capsulitis, it is impossible for us to confirm that they don’t have altered arthrokinematics due to the capsular restrictions. I would postulate that if the posterior capsule was tightening at a greater rate, possibly due to an underlying anterior instability, then the humeral head would be misaligned anteriorly and thus not allowed to glide anterior any further. This leads to the limited external rotation, and a posterior mobilization would be indicated. Even though this goes against the implications of the concave-convex rule, it shows the importance of a thorough clinical exam to determine what is causing the limitation of motion. However, it does not refute the concave-convex rule. Again in reference to Kaltenborn (1989), he states “The most effective mobilization treatments are those that stretch shortened joint structures in the direction of the most restricted gliding.” 

The author’s next claim that Brandt et al (2007) refuted the validity of the concave-convex is egregious. Brandt was simply commenting on the fact that “the active and control subsystems of the shoulder may need to be considered when determining the direction of the translational gliding of the head of the humerus.” Although they did state it may need to be reconsidered, the concave-convex rule was not refuted in anyway. Simply that the indirect method of GH mobilization was not the superior method, as Dr. Kaltenborn already stated himself. He quotes from Kumar et al (2012) the Maitland technique was noted to be an effective additive to exercise for adhesive capsulitis. The study didn’t compare it to any other method of mobilization. 

 Dr. Showalter cited a study by Pollard et al (2008) to advocate for mobilization opposite to that advocated by the concave-convex rule. In the study, the researchers performed the Macquarie Injury Management Group Knee Protocol, and the author references this includes a posterior mobilization. However, the researchers actually performed a caudal thrust. Since the results were of self-reported pain relief and improvement of dysfunction, it doesn’t necessarily refute the concave-convex rule. 

The Scarvell et al (2019) research was truly interesting. The author was kind enough to include a photo figure from the research that demonstrated their findings. I will have you note the femur is beginning at 90° of flexion, visually demonstrating that the anterior glide has already occurred to achieve this joint position. The posterior glide happening in such deep flexion (in a kneeling position, no less) is interesting, but doesn’t refute the concave-convex rule. 

The author’s take home points of refuting the concave-convex rule then transitions to what then seemingly is trying sell the Maitland technique. He claims the Maitland-Australian approach is not a slave to the “rules,” as I agree that treatment should be “evidence informed” and not dictated by the latest literature. I am in no way suggesting one technique of mobilization is superior to another. However, in saying that the concave-convex rule has been refuted, I believe is premature and erroneous.  


  1. Kaltenborn, F., Evjenth, O. & Morgan, D. (1989). Manual mobilization of the extremity joints : basic examination and treatment techniques. Oslo Minneapolis, MN: Olaf Norlis OPTP (Orthopedic Physical Therapy Products) distributor in the U.S.A. 
  2. Neumann D. The Convex-Concave Rules of Arthrokinematics: Flawed or Perhaps Just Misinterpreted? Journal of Orthopaedic & Sports Physical Therapy, 2012; 42(2):53–55
  3. Brandt C, Sole G, Krause M, Nel M (2007) An evidence-based review on the validity of the Kaltenborn rule as applied to the glenohumeral joint Manual Therapy 12 (2007) 3–11 
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