Misunderstood Injury

Lumbrical strains are common, but often impersonate finger-pulley injuries

A mono at Wild Iris, or maybe a slopey pocket on that yellow problem you’ve been working at the gym: You pull, or try to pull, with that ring finger or pinky, the other fingers semi-curled just below it… and feel a zing, right in the palm of your hand.

That’s not good.

You don’t know what you just did, and if someone suggested a lumbrical strain, your first question might be, “What’s a lumbrical?”


What It Is

There are four lumbrical muscles, one at the base of each of the index, middle, ring and pinky fingers. Their function is to bend at the base of the fingers and simultaneously let you straighten the fingers at the middle joints. Imagine pinching a two-by-four and you’ve got it. They can contribute up to 10 percent force production in the hand.

The lumbricals originate from the flexor digitorum profundus (FDP) tendons in the palm of the hand. They insert into the extensor expansion on the back of the fingers. Lumbrical strains are sometimes confused with different finger/hand injuries, such as a flexor- tendon injury, but in recent years our ability to assess them has evolved.

The most common mechanism of injury is the “quadriga effect,” where one finger is straighter while the adjacent fingers are flexing forcefully, such as with a mono pocket or open-handed grip while you “drop” or flex the adjacent finger (usually the ring finger or pinky). According to a hand surgeon, Andreas Schweizer, this strategy increases maximal force of the holding finger up to 48 percent. Pulley tears, by contrast, usually occur in crimping, where the fingers are flexed at the middle joint with the distal joint or fingertip extended.

Symptons

With the injury, pain may arise at the finger close to the knuckle joint (among the major knuckles at the base), possibly on the side toward the thumb, and even into the palm of the hand. Sometimes, with severe strains, you may hear a pop and believe you have injured a pulley.

It is important to differentiate a lumbrical strain from a flexor-tendon strain, although you can experience both simultaneously. With a lumbrical strain, there can be localized tenderness in the palm and potentially in the web space between the fingers. The “lumbrical stress test” can help determine the nature of the injury. Apply resistance to the injured finger with it straight while flexing the adjacent fingers. If you experience pain, you are likely to have a lumbrical strain. With a pulley tear, you should instead feel pain on the palm side of the finger, usually with a crimping grip. Both tests mimic the mechanism of injury.

Diagnostic imaging (ultrasound, MRI) may be necessary to determine the degree of strain. Grade 1 is a mild strain, Grade II involves tearing of the muscle fibers, and Grade III, when disruption occurs most often, is musculotendinous disruption: a tear or partial tear where the tendon meets the muscle.

Photo Steve Graepel
Rehab

Rest! Sorry. But that is what you need.Rehabilitating a lumbrical strain begins with appropriate rest from climbing:

• Grade I strains – expect to rest one to two weeks. • Grade II’s – four to six weeks.
• Grade III’s – six weeks or more.

First in rehabilitation is the remodeling phase, and later you can regain strength.

With Grade I’s and II’s, you may begin gentle range-of- motion exercises within the first week, but not aggressive stretching.

Once you feel that full, pain-free active range of motion is restored, and have no pain with daily activities such as opening your car door, you may begin a gradual loading progression to rebuild tissue strength and durability.

• Grade I’s – you could start in two to three weeks. • Grade II’s – three to four weeks.
• Grad IIIs – four or more weeks.

This loading phase would start with low-load isometrics, first by using a sling/runner as if it is a mono. Adjust the amount of resistance so there is no pain. Hold the isometric for 10-15 seconds each set, two to three sets, three times per week for two to three weeks.

If that is painless, then move on to hangboard progression (unweighted as needed), starting with a three-finger pocket and using the same parameters. If you could do this previously, progress toward holding body weight.

Then progress to a two-finger pocket and repeat, again adjusting weight according to tolerance. Mono deadhangs are strictly reserved for those who were previously at this level.

Remember, the load needs to be very submaximal. The purpose is to remodel the healing tissue. Regaining strength will come later.

Photo Steve Graepel
Returning

When you resume climbing, buddy taping the injured finger to the adjacent finger may help decrease loading and isolation. At first use holds the injured and adjacent fingers can share, to avoid the quadriga effect. Hold off on pockets and open-handed grips that isolate the injured finger until last. With pockets, begin with three-finger pockets, then use two-finger ones, and last try monos.

Prevention

Hangboarding from two-finger or mono pockets to prepare yourself for the positioning is one method, but not everyone is ready for this type of loading. Another option is to use a sling/runner girth-hitched to a weight, and perform an isometric hold in this position. Other specific exercises that can strengthen the lumbricals include using pinch blocks or hanging from pinches with the fingers straight, or deadhangs from slopers using a “cupping”-type grip. Basic exercises include pinching a towel roll or rubber ball as shown in the picture. Last, always hydrate and always warm up, especially if the route requires pulling on pockets.


Also Read

Hamstring Injuries

Speedy Recoveries

  • Zack DiCristino is the lead physical therapist the for USA Climbing Team. He travels to both Open and Youth competitions to ensure the safety and well being athletes. DiCristino currently lives in Salt Lake City and conducts research on climbing-related injuries.

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