Pain Behind My Knee: What Is Causing It?

Pain at the back of the knee is harder to describe than pain at the front. There is no kneecap to point at, and most people call it tightness rather than pain. Most of it is mechanical. One version is not, and that one goes first.

A swollen calf comes first

Pain and swelling behind the knee that carries into the calf is one of the classic presentations of a blood clot in a deep vein of the leg. The calf may look bigger than the other side, feel warm, look red, or be tender, and it can arrive with no obvious cause. The risk goes up after a long flight, after surgery, after days off your feet, and in anyone who has had a clot before. Flights in and out of St. Thomas are long ones, and back pain on long flights covers that side of it.

If your calf is swollen, warm, red or tender, do not massage it, stretch it, or put a foam roller on it, and do not wait overnight to see whether it settles. Get it looked at medically the same day. Working on a clot is not a neutral act. If any of that comes with chest pain, breathlessness or coughing up blood, call 911 or go to the nearest emergency room, because the clot may have reached the lungs. This is not a question you can answer by pressing the leg. It takes a scan and a blood test.

The soft bulge in the crease

A fluid-filled swelling can form behind the knee and sit there as a tight bulge, more obvious when the leg is straight and in the way of full bending and kneeling.

Here is the honest part. It is usually a consequence rather than the problem. The joint makes extra fluid because something inside it is irritated, often a cartilage tear or arthritis, and that fluid pushes back into a pocket already there. Chasing the lump alone misses what set it off.

One of these can also leak or burst. The fluid then tracks into the calf and produces pain, swelling and tenderness that looks very much like a clot. They cannot be told apart by feel, and a known swelling does not take a clot off the table. That is why the clot gets excluded medically rather than assumed away.

Tendon and muscle pain

The hamstrings come down either side of the knee and attach just past it. Pain from one of those tendons sits to one side of the crease rather than the middle, findable with a fingertip, and is provoked by resisted knee bending, sprinting and hill work.

The calf muscle starts above the knee, not below it, so a strain where it begins gives pain lower and more central, usually with a moment attached: a push off, a jump, a sprint for the ferry. Pain in the cord at the back of the ankle is on Achilles tendinitis.

The joint, and the back

The back of the joint line gets sore when the cartilage there is irritated, which shows up with deep bending, squats and kneeling rather than walking. Our knee pain page covers treatment once the source is known, and front-of-knee pain on descents is on knee pain going down stairs.

Less often, the back of the knee is where you feel a problem living in the lower back. Nerve pain refers down the thigh and can land there, though rarely alone. The giveaway is back or buttock symptoms with it, on sciatica.

What narrows it down

Full straightening, deep bending, squatting and kneeling each load different structures back there, so whichever reproduces the pain narrows it. A knee that locks, catches or gives way is a different conversation. And swelling that arrived within an hour of an injury is a different animal from swelling that built over days.

How we sort it out at Tradewinds

At Tradewinds Chiropractic & Wellness in Charlotte Amalie, St. Thomas, the visit opens with the history that matters here: recent flights, surgery, time off your feet, any previous clot, and whether the calf has changed size. If that points at a clot, you are sent for a medical assessment instead of examined further. If it points at the knee, the exam maps where the pain sits, tests the hamstrings and calf, and checks straightening, bending, hip and foot. Dr. Keys is the Chair of the Virgin Islands Board of Chiropractic Examiners, a member of the Virgin Islands Chiropractic Society, and the International Chiropractors Association representative for the U.S. Virgin Islands. Methods are on our services page.

When you should see someone else

Some of this belongs elsewhere:

• Calf swelling, warmth, redness or tenderness. A clot has to be ruled out, and that means a medical assessment the same day. Do not massage or stretch the leg while you wait.
• That plus chest pain, breathlessness or coughing up blood. Call 911 or go to the nearest emergency room now.
• You cannot bear weight on the leg after an injury.
• A hot, swollen, red knee, especially with a fever. A joint infection is urgent.
• A knee that locks, catches or gives way. That needs an exam soon, and usually an orthopedist, since it calls for imaging.

Getting seen

Call (340) 690-4994 to book an exam. We take walk-ins and same-day appointments. We are in the VI Medical Foundation Building, Suite 202, 9150 Estate Thomas, St. Thomas, USVI 00802. Hours are Mon, Wed, Thu: 10:00 am to 1:00 pm and 3:00 pm to 7:00 pm. Tue, Fri: 7:00 am to 2:00 pm. Closed Sat and Sun. New patient forms are online, and Tradewinds has more than 180 five-star Google reviews. If your calf is swollen and painful, do not call us first. Get it cleared medically.

Questions patients ask

What causes pain behind my knee?

Usually one of four mechanical things: a fluid-filled swelling in the crease, a hamstring tendon where it crosses the back of the knee, a strain where the calf muscle starts above the joint, or irritation at the back of the joint line itself. Nerve pain referred from the lower back lands there too, though rarely on its own. Before any of that is assumed, pain behind the knee with a swollen, warm or tender calf has to be cleared of a blood clot medically, and that comes first.

What is the swelling behind my knee?

A pocket of joint fluid can collect behind the knee and feel like a tight, full bulge, more obvious when the leg is straight. It is usually a consequence of something irritating the inside of the joint, such as a cartilage tear or arthritis, rather than the original problem, so treating the lump alone misses the cause. One of these can also leak into the calf and produce pain and swelling that closely mimics a clot, which is why a swollen calf still needs medical assessment even when a swelling behind the knee is already known about.

Why is there tightness behind my knee when I straighten it?

Full straightening puts the structures at the back of the knee on stretch and squeezes anything sitting in the crease, so fluid, a tight hamstring tendon or an irritated joint line all show up in that position. If the tightness is a firm block that stops the leg short rather than a stretch, or the knee catches on the way through, that is a mechanical finding and needs an exam. If the calf is also swollen or warm, that changes the priority entirely.

When is pain behind the knee serious?

When the calf is involved or the knee stops working properly. A swollen, warm, red or tender calf raises the question of a clot and needs same-day medical assessment, and that with chest pain, breathlessness or coughing blood is a 911 call. A hot swollen red knee with a fever, an inability to bear weight after an injury, and a knee that locks or gives way all need a different door than a chiropractic appointment.

Can a chiropractor help pain behind the knee?

For the mechanical causes, yes: tendon and muscle pain at the back of the knee, joint restriction, and the hip and foot problems that load the knee badly. The job of the first visit is to work out which one you have, and to route the clot question out to a physician rather than treating around it. A knee that locks or gives way, or a swelling that turns out to be driven by a cartilage tear, is referred on.