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Lumbrical Strains

Lumbrical strains in climbers are easily confused with A2 pulley injuries, but the causes and treatments differ.

In this article, The Climbing Doc explains how to diagnose lumbrical injuries, manage them effectively, and train wisely to avoid this injury.

Lumbricals vs Climber's Finger

Pulley injuries are far and away the most common hand injury that climbers experience. A2 pulley tears are so common in rock climbers, the condition has been given the moniker “Climber’s Finger” If you’re still not sure you have a pulley injury, go here first.


If you’re fairly certain you avoided a pulley injury but are still experiencing hand pain, you may have injured a lumbrical. Lumbrical strains are much more rare, challenging to diagnose, and can be accompanied by an audible “pop” similar to that heard with A2 or A4 pulley tears. In this article I will explain how to diagnose lumbrical injuries, manage them effectively, and train wisely to avoid this injury.

Lumbricals at work copy.jpg

What are lumbricals?

Lumbricals are small muscles in palm of the hand and function to help flex your fingers. They contribute up to 10% of grip strength and are particularly used in the pinch grip. Lumbricals begin at the base of the palm and end at the base of the fingers. (See the muscles I-IV in the figure below.)  Lumbricals take their origin, or begin, from the long flexor tendons of the hand, and insert, or end, at the extensor expansion of the metacarpophanangeal (MCP) joints, where the fingers attach at the hand.


Lumbricals help to bend the fingers down at the MCP joints, while keeping the fingers straight.  Imagine lifting a laptop computer out of your pack by holding one end with your fingers pointing down, or cupping in a hand crack that is too small for fist jamming.

How are lumbricals injured?

Unlike A2 pulley injuries that often happen in the crimp grip, lumbricals are most often injured in the open hand grip.  Imagine holding on to a pocket with the ring or ring and middle fingers extended while the other fingers are flexed, (see photos below).

dorsal pocket pic.JPG
side pocket pic.JPG

Where does it hurt when the lumbrical is injured?

Anywhere along the course of the lumbrical can be injured, but pain is normally felt in the palm, in line with the injured finger.  More specifically, on the thumb side of the MCP joint of the injured digit, and more pain into the palm of the hand, near the A1 pulley and into the middle of the palm, as shown in the photo.

Pro tip: It is never wrong to see a hand surgeon with knowledge of treating climbers, to help make the diagnosis and treatment plan.  Ultrasound examinations are often helpful too.

Injured lumbrical copy.jpg

How long do lumbrical injuries take to heal?

Much to climbers' chagrin, most soft tissue injuries in the hand, other than gobies, take at least 6 weeks to heal to the point that progressive strength training can begin.  More severe injuries may take 3-6 months to allow unrestricted climbing.

What can be done to help recovery and return to climbing at full strength?

The goal after sustaining a lumbrical injury is to allow it to heal but not get scarred down and lose flexibility in the finger.  To do this the climber should avoid single finger loading in the open (slope) grip and buddy tape the finger to the adjacent finger, (closer to the thumb).  For example, if the ring finger lumbrical is injured, buddy tape it to the middle finger.  Climbing should be avoided if it is causing pain in the hand.  Also avoid heavy manual work.  Once easy climbing is pain free, usually around 1-2 months, gradually advance to more challenging lines / boulders.  Exercises that are good to activate the lumbricals include squeezing a rolled towel with the whole hand, actively clenching the hand into a fist and passively stretching the fingers into the intrinsic minus position using the other hand, which is a 90-degree angle at the DIP and PIP and hyperextension at the MCPs.


What are ways to strengthen the hand to prevent sustaining lumbrical injuries?

After an appropriate warm up, training two-finger open handed grip strength, coupling index and middle fingers (IF&MF), MF and ring finger (MF&RF), and RF with the small finger (RF&SF) using a hang board with progressive loading can allow the lumbricals to get used to these positions before they are required on a climb or a boulder.  After gaining strength and comfort with two finger couples, one can begin developing single finger open (slope) grip strength in a similar stepwise fashion. Single finger crimp strength training is inadvisable due to the increased risk of pulley injuries!

Training pinch grips on hang boards or system boards will keep the lumbricals strong, as will most types of crack climbing, in particular “off-hand” sized cracks.

Core and flexibility training will help you keep your feet on the holds, and therefore is always beneficial.

Bottom line: if your hands or fingers are hurting when you are climbing, stop climbing, cross train, train pushing muscles, (chest and triceps), as well as core training and aerobic conditioning.  Maybe even catch up on some rest.

Schweizer, A. Lumbrical Tears in Rock Climbers. Journal of Hand Surgery (British and European Volume, 2003) 28B: 2: 187–189.

Experience a pop in your finger?

Read more about common finger injuries in climbers.

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