Rock Climbing as a sport has always been dominated by small groups of athletes, although in recent years this has changed. New climbing walls in Spanish cities, more people taking up the sport… but above all, a key turning point has been its inclusion in the Tokyo 2021 Olympic Games. And it looks like this will go further thanks to the Gold Medal won by the spanish athlete Alberto Ginés.
Due to this increase in popularity, associated with the difficulty of the technique and the high loads to which the hands are subjected during rock grips, we are receiving more and more frequent visits to our physiotherapy or occupational therapy practices for possible pulley ruptures or injuries. We must know what to do with this type of patient.
What are the Flexor Tendon Pulleys of the fingers?
The extrinsic musculature of the fingers, such as the Flexor Digitorum Profundus and Superficialis (FDP and FDS), originate proximally in the forearm, and are directed towards the wrist, crossing through the Carpal Tunnel, and each tendon is then routed to its corresponding finger.
These tendons require different finger sheaths to achieve smooth finger flexion mobility; a synovial sheath that allows the tendon to glide, and a fibrous sheath or pulley sheath, that keeps the tendon structure attached to the finger itself. Both structures are present in these tendons.
The fibrous sheath of the finger tendon is confined to the finger itself, and extends from the Metacarpophalangeal (MCP) joint to the distal edge of the volar plate of the Distal Interphalangeal (DIP). It is considered to be an anatomical continuum along this route, although there are areas of concentration of transverse fibres (Annular Ligaments or Pulley A) and oblique fibres (Cruciform Ligaments or Pulley C). The latter are the least robust.
Pulleys A are numbered from proximal to distal, highlighting Pulleys A1, A3 and A5, arranged palmarly to the Volar Plates of the MCP, Proximal Interphalangeal (PIP) and DIF joints, respectively. In addition, we find the A2 and A4 Pulleys, associated with the proximal and middle phalanges. These pulleys are strong structures with great functional involvement, as they hold the tendon in its most critical position, allowing it to work to its mechanical advantage. Pulleys A2 and A4 are of particular importance, as they ensure that the tendons follow the concave axes of the proximal and middle phalanges.
Also, there are the Pulleys C or Cruciform, which are also numbered from proximal to distal. The two most frequently encountered are the C1 and C3 Pulleys, which are found distal to the A2 and A4, respectively. Pulley C1 extends from the proximal phalanx to the Volar Plate of the PIP, and Pulley C3 extends from the middle phalanx to the Volar Plate of the DIP. The C2 Pulley is less frequent and its presence is inconsistent.
If you are interested in the flexor tendon apparatus of the fingers, we have another Post talking about them and Trigger Fingers or Stenosing Tenosynovitis:
How important are the flexor tendon pulleys?
As mentioned above, Pulleys allow tendons to work correctly and remain as close as possible to the finger. In those cases in which this pulley is affected, a phenomenon known as “Bowstringing” may occur, in which the tendon loses the structure that keeps it close to the bone, and loses its flexion capacity. In the long term, joint stiffness may even appear at the interphalangeal level.
Within rock climbing, it seems that the most damaging type of grip for this structure is known as Crimp Grip. Let’s look at what types of grips exist and what implications they may have.
Types of Grips in Rock Climbing
Crimp Grip Position
This type of grip is used to maximise the contact between the fingertips and small contact surfaces. In this position, the PIP is flexed to 90° or more and the DIP is hyperextended. The large forces exerted by the FDS and FDP tendons, together with the large flexion of the PIP, produces a high forces on the Annular Pulleys, which can cause ruptures.
Among the pulleys most commonly affected in rock climbing practice are the A4 pulley (usually the first to break according to cadaveric work), and the A2 pulley (the most commonly reported in the clinic).
One of the advantages of this type of grip for climbers is the ability to use the thumb over the other fingers, which increases grip strength.
Half-Crimp Grip Position
This position is a less aggressive position for the Pulleys than the previous one, and is characterised by a position of relative extension of the MCP joint, while the PIPs are in 90° of flexion and the DIPs are in slight flexion.
Slope Grip Position
This type is often used when reaching small and steep overhangs. In this case, the DIP is in flexion of about 50°, while the PIP is between 20-30 degrees of flexion. It is considered the safest grip for the A2 pulley, compared to the Arched or Semi-Arched Grip.
When this Slope Grip is used with 1 or 2 fingers in flexion, the forces generated by the fingers not involved in the grip are transmitted to those that are, increasing the gripping force. This effect is produced thanks to the Quadriga Effect exerted by the Lumbrical musculature of the hand. Due to its origin at the level of the flexor tendons of the fingers at the level of the hand, the fact that a finger is extended with respect to the one next to it (example: grip with the middle finger extended in an open hand, while the ring finger is flexed), produces an increase in flexor strength in the grip of the middle finger, as this position produces a passive tension of the Lumbrical, which is transmitted to the middle finger, thus increasing its strength in the grip.
Differences in forces between types of techniques in rock climbing
The work of Arif Mithat Amca et al in 2012 evaluated the effect of the three main techniques (Arched, Semi-Arched or Slope) at various depths of the hold, both at the level of maximum voluntary contraction and forces exerted antero-posteriorly and vertically. They obtained these results:
From this work, it was observed that the Slope Grip allows climbers to increase the force exerted progressively with the depth of the hold, while the Crimp or Arched Grip exerts greater force on smaller holds, and reaches a limit for larger holds. With this, we can affirm that the choice of a technique does not depend so much on internal biomechanical factors, but on the aim of optimising the contact-interaction of the finger with the grip.
They also obtained a regression system of the progressive increase of forces in the 3 types of techniques, as a function of the depth of the hold:
Pulley A2 Injury Classification System
Choosing the most appropriate conservative treatment for a Pulley injury is vital for early recovery, whether it is exercise, splints, bandages or immobilisation. However, current classification systems do not facilitate this task. That is why Carrie Cooper and Paul LaStayo in 2020, published this interesting work where they proposed a classification system based on the clinical evaluation of the patient’s hand, based on the signs and symptoms presented by the patient.
The authors use a numerical pain scale such as the VAS from 0-10, so that the patient can represent his or her level of discomfort, at rest, during light activities or sports or work.
2. Active Motion
They then observe the active mobility of the fingers, starting in full extension position. The patient initially flexes the DIP and continues with the rest of the fingers sequentially until the Crimp Grip position is reached. It is not necessary to reach the full clenched fist position, but simply to reach when the DIP and PIP are fully flexed, and the MCP begins to do so as well. From here, the patient returns to the starting position.
3. Active Resistive Motion
The therapist now moves on to individually assess the flexor tendons and the integrity of the A2 pulley, using the various Grip positions mentioned above.
The first option is the Slope Grip, in which the therapist exerts resistance at the volar level of the DIP, while the MCP and PIP are held in relative extension.
The second position is the Half Crimp Position, in which the force exerted by the FDS and FDP is evaluated, exerting direct resistance on the middle phalanx and the DIP at the volar level.
The third one is the Full Crimp Position, in which a full activation of the FDS and FDP counter-resistance at the volar level of the DIP is evaluated. This is the position in which most of the pulley ruptures take place.
Palpation is limited to the area of the A2 pulley and is intended to assess the amount of pressure that is supported by the patient before the onset of pain. The amount of blanching on the therapist’s finger can be used to assess the level of involvement; a) minimal pressure (no blanching), b) moderate pressure (slight blanching) or c) strong pressure (complete blanching).
Taking these four points into account, the authors propose to divide the condition into three levels of severity of the condition of the A2 pulley, thanks to the following table:
In this way, treatment for Severe affectations will involve rest and immobilisation, gentle mobility and important modifications in the patient’s activity; Mild, where active work will be proposed with a programme of exercises with progressive resistance and training of the gesture. In the moderate stage, a more moderate intensity in the exercise programme will be considered.
Pablo Rodríguez Sánchez-Laulhé
Physiotherapist and Health Researcher
Schöffl I, Oppelt K, Jüngert J, Schweizer A, Neuhuber W, Schöffl V. The influence of the crimp and slope grip position on the finger pulley system. J Biomech. 2009;42(13):2183–7.
Schweizer A, Hudek R. Kinetics of crimp and slope grip in rock climbing. J Appl Biomech. 2011;27(2):116–21.
Cooper C, LaStayo P. A potential classification schema and management approach for individuals with A2 flexor pulley strain. J Hand Ther. 2020;33(4):598–601.
Amca AM, Vigouroux L, Aritan S, Berton E. Effect of hold depth and grip technique on maximal finger forces in rock climbing. J Sports Sci. 2012;30(7):669–77.