Patella Problems and Injuries

Anatomy and Function of the Knee

Before you start, it will be very helpful to read our knee anatomy information so to better understand the knee, where the patella (knee cap) is located, and how the knee works. You can always refer to this information later in the article.

Anatomy and Function of the Patella

The patella, or kneecap, is the loose, moveable bone on the front of the knee. The patella is a link between the pelvis, hip, and foot. The patella is part of the extensor mechanism of the leg; the extensor mechanism acts as a stabilizer when we straighten our leg. This mechanism is composed of the quadriceps, the quadriceps tendon, patella and patellar tendon. The patella gives power to the quadriceps muscle on the front of the leg. In order for the patella to track up and down normally in the patellofemoral groove formed by the medial and lateral condyles, there has to be balance on both the lateral (outside) and medial (inside) side of the patella as the patella moves up and down the groove throughout the knee’s full range of motion.

The underside of the patella is covered with articular cartilage, which is a smooth, spongy covering on many joint surfaces. This slippery surface helps the patella glide inside the patellofemoral groove in the femur.

How The Patella Causes Knee Problems

Problems develop when the patella suffers wear and tear. The underlying cartilage begins to soften, called chondromalacia patellae. Wear and tear can develop for several reasons. Degeneration can develop from generalized wear and tear—similar to putting a lot of mileage on a car. Problems can also be caused when the muscles on the front or outside of the thigh are way too tight.

A very common knee problem is when the patella moves as the knee bends or straightens. This happens because of a muscle or structural imbalance. Normally the patella moves along a path controlled by the quadriceps muscle. If the inside of this muscle group is weak, a muscle imbalance occurs, and the patella can move from its normal path. In time this abnormal movement can cause wear and tear to the cartilage.

A structural imbalance can exist if there are variations in the anatomy of the bones in the leg or the angle at the knee joint made by the femur and the tibia. Women tend to have a greater angle than men. The patella sits in the femoral groove at the center of this angle. When the quadriceps muscle contracts, the muscle tries to straighten this angle, and pushes the patella out of the groove to the outside of the knee. If this angle is increased, the patella tends to shift outward with more easily.

Another variation in the leg bones can happen when the femoral condyle is smaller than normal. The femoral condyle on the outside part of femur normally keeps the patella in the patello-femoral groove. If the femoral condyle is too small, the patella has a tendency to slip outward.

By viewing the knee joint on end, it’s easy to see how this shift affects the patella. As it slides through the femoral groove, the patella shifts to the outside. This places more pressure on one side of the underlying cartilage than the other. In time this pressure can cause damage to the articular cartilage.

Symptoms Of Patellar Problems

Bones of the knee jointMost patients with chronic patellofemoral problems complain of knee pain when squatting, going up and down stairs, getting up after sitting a while, popping, giving way, a crackling sound in the knee, and possible mild fluid (blood or synovial fluid) on the knee.

Chondromalacia patellae exists when there is softening of the cartilage, which may develop into small fractures in the underside bone of the patella. Some people never have problems with this condition. Others have vague pain in the knee that is hard to figure out where the pain is coming from. Pain may or may not be felt along the inside edge of the patella. Typical complaints include pain when walking down stairs or hills, keeping the knee bent for long periods as in the car or theater, or with pressure to the patella. The knee may feel as if it gives out on occasion, but this is thought to be a reflex response to the pain and not an indication of instability in the knee.

The knee may feel like it’s grinding or your may hear grinding when squatting or going up and down stairs. If there is a lot of wear and tear, you may have a feeling of popping when you bend your knee. Popping and grinding can happen when the uneven surfaces of the patella and the femoral groove rub against each other.

How Are Patella Problems Diagnosed

Diagnosis begins with a complete history, which is your story of your knee problem including did you have an injury and when does it cause you problems. An examination of the knee is done, including the patella to find out the source of your pain and to find the position of your patella. You may be examined standing, sitting and lying down. Muscle strength will also be tested for muscle imbalance that can affect tracking of the patella. Xrays are done on your first visit with the orthopedist. An xray helps decide if the patella is in staying in the normal groove when the knee moves. As chondromalacia progresses, arthritis may be seen between the patella and femur. Chondromalacia is sometimes mistaken for other knee problems because the cause of the symptoms are hard to pinpoint. In these cases, other tests may be done. An MRI scan can help rule out other conditions like a torn cartilage or bone damage.

A physical therapy exam can help decide whether a muscle imbalance or other alignment problem is present. A physical therapy program may be able to resolve symptoms.

If symptoms persist, knee arthroscopy may be needed to diagnose the exact cause of your problem. The arthroscope allows the surgeon to look into the knee joint and actually see the condition of the articular cartilage on the back of the patella.

What Are The Treatments For Patella Problems

The Initial treatment for a patellar problem starts by reducing pain and swelling in the knee before. Strengthening exercises done with a swollen knee can inhibit contraction of the quadriceps causing weakness and wasting of the muscle. Rest and anti-inflammatory medicines, such as aspirin or NSAIDs, can help reduce pain and swelling.

In the early stages, physical therapy can help reduce pain and inflammation. As symptoms are controlled, your physical therapist can offer several treatment choices to correct problems with flexibility, strength, alignment, and muscle balance in the knee and leg.

If non-surgical treatment fails to improve your condition, surgery may be needed. A lateral release may be done to allow the patella to move back into its normal track and relieve pressure on the articular cartilage. In a lateral release, the tight lateral ligaments on the outside of the patella are cut to allow the patella to move towards the center of the femoral groove. These ligaments heal over with scar tissue and fill in the gap created by surgery. Looking at the end view of the knee shows how loosening these ligaments relieve pressure on the articular cartilage.

In cases of more severe misalignment, a lateral release alone may not be enough. The tendons on the inside of the knee (the medial side) may have to be tightened, pulling the patella to the center of the groove.

In very severe cases where the patella keeps dislocating, the attachment of the patellar tendon may also have to be moved. Once the surgery heals, the patella will track up and down in the patellar groove, reducing pressure on the articular cartilage.


  1. I was in a car accident 28 years ago. Fractured my right femur, right pelvis, pubic bones, tailbone, peroneal nerve palsy, both lungs collapsed and traumatic head injury. The nerve damage caused ultra sensitivity from knee down and drop foot. Myfoot felt like it was in a pan of boiling water for years. Anything that touched it exacerbated the pain, socks, shoes, water, blankets, even the air. I was in the hospital for 2 months. In the hospital, I held my foot in my arms up to my chest to keep anything from brushing against it. I’m not sure why I was allowed to do this. My femur healed malrotated 90° and my tendons and ligaments behind my knee shortened so I couldn’t straighten my leg. My pelvis, pubic bones and tailbone all healed misaligned . I was in a wheelchair for over 2 years before they did the corrective surgery to straighten my femur, but they didn’t correct the rest. 16 months on crutches, another year back in my wheelchair, 14 months on crutches. Early 1997, I was upright with a foot brace. Within a few months, the knee pain started. The inside of my knee hurt with every step. If I layed down on my left side, it felt like my bones were pinching ligament. On my right, it felt like it was separating. I have seen dozens of doctors, orthopedics, endocrinologists, neurologists. I have had over a dozen MRIs, multiple CT scans, atleast 20 cortisone shots, 3 arthroscopic surgeries, several dozen arthritis meds, anti-inflammatories, muscle relaxants, pain killers, nearly 100 needle aspirations….none of it has helped. Now, the cartilage is completely worn away. It hurts to walk, sit, stand and lie down. I slide my foot when I’m walking to keep my knee from separating when it comes off the ground. I was scheduled for a total knee replacement but they cancelled it when my doctor actually looked at my knee without xrays. I have an 8° femoral neck anteversion, my knee is externally rotated over 35° but my tibia and foot are straight. I wish someone had answers. I’m tired of being a big pharma guinea pig. Thoughts?

  2. MaryAnn Fox says

    Hi, I broke my left knee cap 20 years ago. I never had any problems until recently when I sprain my LCL ligament On my right knee. I had to use crutches for almost three months therefore my left knee took all my weight. So now, whenever I’m getting up, walking up a hill or walking for a long period of time it really hurts. Can just three months of over using my left knee cause so much damage that now it hurts on the daily? My doctor said it’s because I lost my muscles around the knee that’s why it is hurting. I’m wondering what kind of exercises I should do to strengthen the muscles around my left knee. Can’t do squats they cause more pain. Thank you!

  3. Sergei simon says

    Hi Doctor
    My daughter was born with a deformed patella ( where our knee cap is in its right place, hers is slightly a little higher), which cause her not to be able to straighten the leg At all, so she’s walking with a limp. Can surgery be done

  4. Angela Younger says

    My doctor I went to told me my joints in knees look good but my knee caps are worn out and rubbing against bone and I should lose weight to see if that helps cause he couldn’t do anything.

  5. I have noticed for a while that when I walk it feels like my knee cap has slid down. My mother has taken me to a physio and we’ve had an X-ray and nothing has shown up. Could this maybe be whats causing the pain?

  6. James grooms says

    My knee has popped out the times in the past two months. If I get on my knees at work to plumb a sink or anything it pops out. When in get up I can’t walk. I got to bend it back and forth then it pops back into place. What is going on? I’m 44 and never had any knee problems.

  7. My knee cap can move up and down + left and right.. I don’t know if it’s broken or if it’s just normal.. and when i stand up, i can move it up without touching it. Please give me some advice. Thank you.

  8. Years ago I was playing a 2-on-2 game of street basketball. I was driving to the hoop for a lay-up, getting by this kid, he then kicked my left knee out on purpose and my patella/kneecap was completely dislocated.

    So I am on the ground in excruciating pain and everyone is freaked out because they have never seen an injury like that before. So I go to try and adjust my leg and there was a loud POP. My kneecap slid back in place and surprisingly felt OK. I could move it and all. I even refused the ambulance when it had arrived because I thought I was OK. Til the swelling began to kick in….

    So of course I wound up in the hospital because my knee swelled up to the size of a volleyball. They just gave me 1 Vicodin with no prescription for more, which sucked. They also just gave me a knee splint, and some papers about the R.I.C.E healing method (Rest Ice Compression Elevation).

    I was completely immobilized for 3 weeks. Since I didn’t have meds for the pain, the healing time was one of the absolutely most painful periods of my life!

    3 weeks later I thought I was good enough to move around as long as I wore a brace. One day, I was getting ready to leave the house and out of nowhere the loud POP sound came, and down to the ground I went. So I wasn’t fully functional after 3 weeks, and it took about 6 months for the swelling to subside and make my knee not look slightly deformed any more.

    Years later now, I notice my knee still tries to slide out of place. If I tweak it bad enough it will almost try to slide out all the way. It just happened to me yesterday. It hurt so bad, now I have some pain and swelling on the inside of my knee. It hurts when I crouch and turn corners mostly.

    My question is, since this is a chronic problem (14 years later after initial injury) does this constitute needing surgery ?

  9. Hey! I see some stories of people saying ‘’ I went to the doc and he said he can’t do anything for me” if you honestly think it’s bad go and see someone els!!

    My doc told me that and I just left it. When I would bend down my right knee would grind not crack it would make a loud 1second grinding sound. After 9months seeing him I jumped onto a small stage and dislocated my right knee. I needed surgery and had loose bone fragments and cartilage. Got a latteral release done and have level 4 (highest) wear and tear on kneecap. It’s been 2 months swine surgery and still not back on track. Keeps getting stiff after being on in for 3+ hrs and starts to hurt after 5hrs. Hurts when I try and lift it up while the leg is straight. Still going back to the doctor every month per his request.
    I’m 26 haven’t had a if sports life.

    Always get a second opinion

  10. what can I do for the patella against shin bone

  11. My dr said to give up running and cycle to build up the quads. To balance the muscles

  12. MAULIK PARIKH says

    I am facing, the problem, exaclty the way it is written out here. it looks like my story, word to word. I am 46yrs and am a long distance runner and a tri-athelete. as said here, the medicines do give a relief but not a cure. it seems, the strength of the muscles surrounding and attached to my patella is unequal and not properly structured, may be because of impropermuscle development on account of my long distance activity. i fear a surgery, as i feel it might disturb the natural setup of my knee design, and would not be able to run again. the pain is bearable but resting without any daily workout, over this last 4months is a big agony.

    if anybody can direct me to the correct ailment, i would be deeply obliged

  13. My left. Knee keep pop and cracker a lot I went the doc I did threpy for it it didn’t help made it worst go back my doc he want me to MRI I did that after he told me that he can’t do anything for me I’m reading this and sound like it can be fix I’m a running I can’t run anymore I’m 37 years old

  14. hello
    dr. i had my kneecap operation before 2yrs, my kneecap is removed as it was broken into 5pieces. but till now i m not able to walk properly. i can only band my leg to 15degree.
    i really want to be like a normal boy i want to live my life normally like others. please help me. please tell me what should i do to get the movement!!
    i m going in depression day by day. please help me!!

  15. My Dr said that I may have burst a cushion in my knee but he wanted the x-ray and ultrasound back before speculating on options. When I was 39 weeks pregnant I had a fall and protected my belly by landing on my left knee. The knee was very swollen and bruised immediately after the fall. The knee is still swollen after 6 weeks as past since the injury happened. Does a knee cushion repair its self or does it need medical intervention?

  16. Regarding patella knee problems what sort of exercises should be conducted to help or elevate this problem?
    Thank you

Speak Your Mind