This topic discusses pain in one arm or leg. It could be from an injury, or start on its own. Here we don’t describe specific body parts (knee, forearm, etc.), but rather illustrate how we can identify the body structure involved (e.g. bone, tendon, etc.), wherever it might be. For generalized pain all over, see separate topic Body Aches. For Back Pain or Neck Pain, see those symptoms. See also Joint Pain if it’s a joint that hurts.
Someone has pain in an arm or leg — Can’t we just get an X-ray? No, not really. X-rays can detect bone disease, like fractures, bone tumors, & sometimes bone infections. They can show arthritis that’s advanced. But they can’t find the most common causes of pain, like sprained ligaments, strained tendons, or bursitis.
An MRI can identify major tears (which we can invariably suspect from examination), but not the more common minor injuries. But even worse, they’re notorious for false-positive findings. One study found 97% of adults with no knee pain have MRI abnormalities. Another found the same for 98% of shoulders. So for a patient with knee or shoulder pain, if the MRI is abnormal, there’s no proof at all that it’s the cause of their symptoms!
The following discussion details what a brilliant physical therapist taught me in Kentucky. There are no studies to prove it accurate, and the key points are meant as guides, not absolutes. Ambiguous findings are common; what helps best is identifying which maneuver on exam elicits the most pain. Still, the systematic approach is enormously helpful in determining who may need an x-ray, & clarifying symptoms to both examiner & patient alike.
Let’s say a patient comes to see us for “forearm pain” as a typical limb. What body structures might be involved?
BONE — This is our main concern — Bone Disease is the worst. A fracture probably needs casting. Bone infections & tumors are nasty. How do we tell if pain comes from bone?
Percussion! I’ve never had a fracture myself, but can imagine that the last thing I’d want would be for someone to pound on it. However, we start gently. Look First — If we see an obvious gross deformity, don’t touch! Get an x-ray.
Say there’s no deformity, and we see swelling on top of the arm. If gentle palpation is tender, we won’t hit harder. But maybe it’s just swelling from a bruise under the skin, nothing to do with the bone. So we palpate, & then percuss, from underneath — in other words, attack the bone from a different angle to avoid the obvious point of injury. If we can percuss & then pound the bone that way, the bone’s likely OK.
We might also try jarring the elbow, or the wrist, & see if it provokes pain at the point of concern. If so, might be the bone (vibrations carry through bone).
Depending on the injury, or location, we may have to invent ways to explore for possible bone involvement. But ultimately, the bottom line is the same — if we can percuss or even pound on the area in question, without it hurting, the bone is probably fine.
This principle can be used for other sites. Low back pain? We lightly palpate each vertebra in the spine. If that’s not tender, we palpate more firmly. Still non-tender? Percuss gently. Percuss harder. Pound! If that doesn’t hurt, it’s not bone cancer or spinal abscess.
Note — When we use this principle for acute trauma, we need beware of outside factors that ruin it. If the patient is mentally “altered” (like drunk, or has a concussion), we can’t count on this exam to rule-out a broken neck. The same holds true if there’s a larger, painful, distracting injury elsewhere — a big broken leg might mask the pain from a small (but potentially paralyzing) fractured spine. See Neck Fracture.
The worst kind of fracture (aside from the neck) is an “open” or “compound” fracture. They mean the same: a fracture with a wound deep enough to communicate with bone. If so, there’s great risk of bone infection, causing permanent disability. It’s not immediately life-threatening, but the patient needs IV antibiotics ASAP. The bone doesn’t have to be sticking through the skin or be visible, as long as the wound seems deep enough for outside germs to reach it.
JOINT — The knee is swollen, maybe even reddish or warm. How do we determine if this is joint disease (worst case: Infected Joint), or due to a structure around but not inside the actual joint, such as tendon, bursa, etc?
Affected joints hurt when they move. Conditions include Osteoarthritis and Inflammatory Arthritis (Rheumatiod Arthritis, Gout, etc.; see Joint Pain). But active range of motion (AROM) involves lots of structures. I usually find AROM non-helpful diagnostically. It’s fine for a ballpark idea of how one copes with injury, but except for perhaps bursitis, won’t sort out one structure from another.
Passive range of motion (PROM) is the key. If the patient can relax well (which may be hard), we support the affected area however possible, and gently wiggle the joint to and fro. Not tender? Slowly wiggle it further. If we can carry a joint through much of its PROM, say from bent to fully extended straight, without any tenderness, a joint condition is unlikely.
However, swelling around the joint from whatever condition will often cause uncomfortable external pressure when the joint bends. If the patient begins to flinch at that point — we Pause. Then smoothly move the joint all the way in the other direction to completely straighten it. If the latter movement doesn’t hurt, there’s no joint disease [because we will have fully manipulated the joint without a problem].
LIGAMENT — Passive ROM will also elicit tenderness from a sprain, but only in the direction that stretches the ligament. So if the ligament on the outside of the ankle is partially torn, passive inward ankle movement will hurt. But passive outward movement, or bending / straightening won’t. In joint disease (like gout), all the PROMs, whatever direction, will hurt (because the joint is being manipulated).
Injured ligaments (Sprains) are tender to direct palpation, but not to tapping the joint from the other side. Try that to any area of a joint with acutely inflamed arthritis, and we’ll get a response!
TENDON — Testing strength against resistance maximizes the pain of a strained or inflamed tendon. We do this by holding the joint still, and pulling on the distal part of the limb while the patient resists as strongly as possible. This puts the tendon and muscle in full use.
By holding the joint still, strength against resistance only involves tendon and muscle. The location of provoked tenderness will distinguish between those structures. Pain over the tendon or joint area is the tendon, pain further up the arm or leg (proximal) is the muscle. [Obviously, we don’t attempt this until we’ve pressed & pounded on the bones to be sure there’s no injury or disease there).
Passive ROM barely bothers tendons, because they aren’t actually doing anything. Active ROM may hurt with tendon injury, but will also hurt with ligament, joint, bone, muscle, bursa, & even skin & soft tissue diseases or injuries, because all the structures are being manipulated.
Testing Strength Against Resistance
#1 above: The examiner holds the forearm steady, and has the patient bend her wrist back hard against resistance. If this hurts in the wrist, there’s a tendon strain or tendonitis. (If it hurts in the forearm, where the muscle is located, it’s a muscle strain.) Note that the wrist joint itself isn’t moving; only the muscle & tendons are active.
#2 above: The examiner holds the upper arm steady, and has the patient bend her elbow hard against resistance. If this hurts in the crook of the elbow, there’s a tendon strain or tendonitis. (If it hurts in the upper arm, where the muscle is located, it’s a muscle strain.) Note that the elbow joint itself isn’t moving; only the muscle & tendons are active.
MUSCLE — Muscle Strains also hurt when testing strength against resistance. But the tenderness is upward from the joint (proximal). If, say, bending elbow against resistance hurts in the upper arm over the biceps, that’s muscle. If the pain is felt down by the front of the elbow, it’s tendon.
BURSA — These are fluid-filled sacks near bony prominences that protect our soft tissue, and get inflamed by repetitive motion or pressure (Bursitis). Bursae (plural) are found all over, near joints.
We suspect bursitis when pain occurs at location of a bursa. Active ROM in any direction is tender, but Passive ROM shouldn’t hurt. Superficial bursa may swell. There’s often point tenderness to palpation, though some bursa are too deep to provoke by palpation.
FASCIA (COMPARTMENTS) — “Compartment Syndromes” are uncommon but potentially devastating. Pressure accumulates under inflexible fascia, causing permanent damage to tendons, nerves, or arteries. This usually happens soon after trauma, commonly fractures but also crush injuries, and very rarely minor trauma or spontaneous bleeding (perhaps among people taking anticoagulants, called “blood thinners”), Rapid surgery is essential to preserve function and even limb.
We’d suspect a Compartment Syndrome when local pain, usually out of proportion to minor physical findings, progresses rapidly after trauma. Distal symptoms, downstream from the injury, are the key (like broken shinbone, with symptoms in the foot!). Tingling is often the first symptom. The local fascial compartment swells; distal sensation and then motor strength diminish. Any hint requires immediate measurement of compartment pressure: We send right to ER [& they’ll send to OR].
In the leg, a key finding for Compartment Syndrome is loss of sensation in the web between the first two toes. If they can’t feel us touch them there, especially with a sharp point like a pinprick, they may need immediate surgery.
SKIN & SUBCUTANEOUS TISSUE — Bruises (contusions & hematomas) from trauma cause pain. We distinguish this from fractures as described above under BONE.
Imagine the front of the knee is red and hot — is it a skin infection (Cellulitis), or a type of arthritis [infected arthritis, a.k.a. Septic Arthritis, as a worst case]? Both may hurt with palpation. Passive ROM will hurt with arthritis, but may also with cellulitis due to skin manipulation.
So we improvise. Manipulate the skin very superficially; if this elicits tenderness, we think cellulitis. Then we passively bend the knee, causing pain with either condition. Pause, then gently passively straighten the knee slowly. This may relieve the pain from having stretched infected skin, but will hurt equally if there’s joint disease.
To distinguish kneecap bursitis from infection, we’d try manipulating the skin at the edge of redness furthest from the bursa [tender with cellulitis]. We palpate different areas within the redness: all will hurt if it’s cellulitis, but only the point directly over the bursa will with bursitis.
Again, none of these maneuvers is scientific, validated, or exact. But they’re helpful, especially in terms of underlying principles. Unfortunately, many clinicians aren’t familiar with them.
ONE LAST PUZZLER: Reflex Sympathetic Dystrophy (RSD) — In my Kentucky ER in the early 1980s, a patient came in with a painful, cool, swollen hand. He’d accidentally hit it with a hammer months before, but x-ray was normal (no broken bones). The skin was shiny. He explained how this had occurred on and off since his injury, but whenever he saw a doctor or even a specialist, the hand was normal. I actually got to see it swollen.
RSD, not widely known about back then, is now called “Complex Regional Pain Syndrome (CRPS)“. As with many conditions (“syndromes”) with vague-sounding names, nobody knows what causes it (click for explanation of what “Syndrome” means). With RSD / CRPS, nerves have likely been injured, and stimulate activity of lots of hormones & other body chemicals. Maybe the brain even plays a role. The condition can occur after accidents, strokes, heart attacks, surgery, & in over 1/3 or cases, nobody-knows-what.
The skin can experience texture & temperature changes. Eventually bone can waste away (osteoporosis). Treatment is difficult (as with most diseases of unknown cause).
See also Musculoskeletal Pain for the clinician’s condensed thought-process when face-to-face with a patient.