Pain at the bottom of the knee, just below or around the lower edge of the kneecap, is most often caused by irritation of the patellar tendon, the thick band of tissue that connects your kneecap to your shinbone. But several other structures sit in this small area, and pinpointing which one is the source matters for getting the right treatment. The most common culprits are patellar tendonitis, fat pad impingement, and in younger people, a growth-related condition called Osgood-Schlatter disease.
Patellar Tendonitis (Jumper’s Knee)
This is the single most common reason adults feel pain at the bottom of the knee. The patellar tendon runs from the lower edge of the kneecap down to a bony bump on the top of the shinbone, and when it gets overworked, it develops tiny tears that accumulate over time. Most people describe the pain as a low, dull ache right at the front of the knee, with tenderness to even a light touch just below the kneecap.
The pain typically gets worse when you use or straighten your knee. Climbing stairs, squatting, and lunging are common triggers. It’s a repetitive strain injury, meaning the damage builds up gradually rather than from a single incident. Repeated jumping, sprinting, or a sudden spike in training volume are the usual causes. If you recently increased your activity level or started a new sport, that’s a strong clue.
Recovery depends on severity. Mild cases can improve in about three weeks with rest and modified activity. More severe tendonitis, where the pain has been present for months or limits daily tasks, can take three months or longer. The key is giving the tendon time to heal while gradually reloading it, not simply resting until the pain disappears and then returning to full activity.
Fat Pad Impingement
Directly behind the patellar tendon sits a cushion of fatty tissue called Hoffa’s fat pad. When this tissue gets pinched between the kneecap and the thighbone, it swells and becomes a persistent source of pain. The tricky part is that fat pad impingement feels very similar to patellar tendonitis: anterior knee pain right near the lower edge of the kneecap.
One distinguishing feature is that people with fat pad impingement often stand with their knees slightly hyperextended, or “locked back.” The pain tends to flare when the knee is fully straightened rather than during loaded bending. A clinician can test for it by pressing on both sides of the lower kneecap with the knee slightly bent. If that reproduces your pain, the fat pad is likely involved. Because the two conditions overlap so much, fat pad impingement is sometimes only confirmed after a local anesthetic injection into the fat pad relieves the pain.
Osgood-Schlatter Disease in Young Athletes
If the person with bottom-of-knee pain is between roughly 11 and 14 years old, Osgood-Schlatter disease is a likely explanation. During growth spurts, the patellar tendon pulls on the bony bump (tibial tubercle) at the top of the shinbone before that bone has fully hardened. The result is a hard, painful lump just below the kneecap that’s tender to touch and worse with running, jumping, or kneeling.
A related condition called Sinding-Larsen-Johansson syndrome causes similar symptoms but at the opposite end of the tendon, right where it attaches to the bottom of the kneecap itself. Both are self-limiting, meaning they resolve once growth slows down, but activity modification and ice help manage pain in the meantime.
Could It Be Something Else?
A meniscus tear can sometimes cause pain that feels like it’s at the bottom of the knee, though meniscus pain is usually felt more along the sides of the joint, right at the level of the space between your thighbone and shinbone. The hallmark signs are a locking or catching sensation when you move the knee, a feeling that the knee might buckle, and pain that worsens with twisting or pivoting rather than with straightening or squatting. If your pain started after a specific twisting injury and you notice the knee catching, an MRI can confirm or rule out a tear.
Less commonly, irritation of the tissue lining the joint (the synovium) around the kneecap or strain on the bands of connective tissue on either side of the kneecap can produce pain in a similar location. These are harder to self-diagnose and usually require a hands-on exam.
What You Can Do at Home
For most causes of bottom-of-knee pain, the initial approach is the same: reduce the activity that provokes it, apply ice for 15 to 20 minutes after activity, and avoid prolonged kneeling or deep squatting while symptoms are acute.
Once the sharp pain settles, progressive loading exercises are the most effective long-term strategy for patellar tendon problems. Research published in the British Journal of Sports Medicine tested a structured program that starts with isometric holds (pushing your leg against resistance without moving the joint) at about 60 degrees of knee bend, held for 45 seconds at a time, repeated five times. The goal is to gradually increase the load on the tendon in a controlled way, progressing through stages based on your pain level. A good rule of thumb: exercises should be mildly uncomfortable but not produce pain above a 3 out of 10.
Eccentric decline squats are another well-studied option. These are done on a sloped surface angled at about 25 degrees, slowly lowering yourself on the affected leg while using the other leg to push back up. This targets the tendon during the lengthening phase of the movement, which stimulates healing. Both approaches require consistency over weeks, not days.
Signs That Need Prompt Attention
Most bottom-of-knee pain is manageable with activity modification and rehab exercises, but certain symptoms point to something more serious. Seek urgent care if your knee joint looks visibly deformed or bent out of shape, if you heard a popping sound at the time of injury, if the knee can’t bear any weight, or if it swelled suddenly and significantly.
You should also get evaluated if the knee is red, warm, and tender to touch alongside a fever, which can signal infection. And if lower-grade pain is disrupting your sleep or making everyday tasks difficult for more than a couple of weeks, that’s reason enough to get it checked rather than pushing through.