Sharp knee pain can be extremely unpleasant, often stopping people in their tracks. It usually indicates a problem in one of the knee bones, or the surrounding neural structures. Sharp pain can also occur when there is damage to the soft tissues in and around the knee.
Sharp knee pain is often fairly short lived, coming on suddenly with a particular movement and then easing quickly when you stop the aggravating activity.
In some cases the sharp pain in and around the knee will persist, but often it either settles completely, or eases leaving behind a residual, ongoing ache or throbbing type pain.
When the sharp pain is confined to the knee joint, it usually indicates a problem in the knee joint itself such as a soft tissue injury or inflammation of the joint. If it accompanied by a shooting pain that travels down the leg, that usually indicates a neural problem either at the knee itself, or in the lower back.
The most common causes of sharp knee pain are:
Here we will look at the common causes of sharp knee pain, how they present and how to work out what is going on in your knee. We then look more in-depth at how to treat these different causes of sharp pain in the knee.
Injuries to the soft tissues in the knee are the most common cause of sharp knee pain. Most typically sharp pain develops when there is damage to the cartilage lining the knee joint or inflammation in the knee bursa.
Sharp pain in the knee is most commonly caused by something getting stuck in the knee joint.
The surface of each knee bone is covered in a thick layer of cartilage which allows smooth, pain-free movement by working as a spacer between the joints so that as the knee moves, there is no friction on the bones. The knee cartilage also works as a shock absorber to reduce the forces going through the knee with activities such as running and jumping.
If this knee cartilage gets damaged, then small fragments can tear off and get stuck in the joint.
There are two ways this can happen:
When a loose portion of cartilage gets stuck in the joint, it typically causes a sharp pain and often results in locking, where the knee joint gets stuck and you can't move your leg. Usually after a few seconds of wiggling the knee around, the cartilage moves slightly and once the fragment is no longer stuck, the pain subsides and the knee moves freely.
You can find out more about the causes, symptoms, diagnosis and treatment options in the Knee Cartilage Injuries section.
Knee bursitis is another cause of sharp knee pain and can affect any part of the knee.
Around the knee are various fluid filled sacs, known as knee bursa, which sit between soft tissues and bone to reduce friction and pressure on the knee structures.
If the bursa get inflamed and then squashed, it can result in a sharp pain in the knee.
The location of the pain indicates which bursa is affected. If the sharp pain is at the:
You can find out loads more about the different types of bursitis, how they present and how to treat them in the knee bursitis section.
There are also a number of bone problems that can cause sharp knee pain. There are three bones associated with the knee which form two separate joints.
A sharp pain in the knee may be a sign of wear and tear inside the joint. Damage to the cartilage, either through wear and tear causing it to thin and fray, or through an injury which causes it to tear, can lead to the formation of osteophytes, small lumps of bone which stick out slightly.
These osteophytes reduce the space between the bones and without the cartilage to protect and cover them, bone rubs against bone. This typically leads to arthritis.
When the knee moves, there is friction and pressure on the osteophytes which results in sharp knee pain. In this instance, the sharp pain comes on quickly when the knee moves into a position that places pressure on the osteophytes, typically with activities where there is weight going through a bent or twisted knee.
Once you move the knee into a different position and relieve the pressure on the osteophytes, the sharp pain goes away, but it may leave a residual aching pain.
Often, walking itself feels ok, but when you add any extra pressure to the knee joint such as squatting, twisting, running or going up and down stairs, that brings on the sharp knee pain.
If the sharp pain gets worse going upstairs typically indicates a problem with the tibiofemoral joint, whereas if your sharp knee pain is worse coming down the stairs it is more likely to be a problem with the kneecap.
You can find out all about the common causes, symptoms, diagnosis and treatment options in the Knee Arthritis section.
Sharp knee pain can also occur when something gets stuck in the knee joint as it moves. In most cases, it is a small fragment of bone that gets stuck, typically a osteophyte that has broken off. Alternatively, it could be a small fragment of cartilage that has torn off the meniscus.
One or more of these small fragments, known as loose bodies, may be floating around within the joint capsule. It may at times get trapped in the joint causing sharp knee pain and may even cause the knee to lock. Once it moves out of the way, the pain typically subsides and normal knee movement returns.
Pain from a loose body tends to be intermittent rather than constant. It won’t happen every time you do a certain activity, it will most likely catch you off guard when you are not expecting it. You can find out loads more about how cartilage tears cause sharp pain in the knee and how to treat them in the meniscus tear section.
If there is severe sharp knee pain, that is unrelenting and started due to an injury may indicate a break in one of the knee bones.
With a broken bone, there is often considerable swelling and there may be an obvious deformity. Any movement of the bones, however small, is likely to produce a severe, sharp pain in the knee as the broken pieces of bone rub on each other.
It takes a lot of force to break one of the knee bones so you normally know straight away that something is wrong.
The break may be in either the tibia or femur, or if you have fallen onto the front of the knee, there may be a patella fracture.
Sharp pain in the knee can also be caused by a neural problem - something wrong with one of more of the nerves travelling from the spine down to through the legs.
Our nerves are like electrical cables and run all over our body. The nerves of the leg arise from the bottom part of the spine branching out to the different parts of the thigh, knee, calf and foot. They transmit messages from the brain and spinal cord to the muscles to tell them what to do and carry signals regarding sensation such as pressure, pain and temperature.
If a nerve gets squashed or irritated, we typically experience a sharp pain. This may be felt locally at the point where it is trapped, or it may also travel further along the path of the nerve, feeling more like a shooting pain. The sharp pain may also be accompanied by pins and needles or numbness or in more serious cases muscle weakness.
Nerve pain can be due to the nerve getting squashed or trapped, for example by an osteophyte, a particularly tight muscle or a disc bulge in the spine. The nerve can also get irritated if it is surrounded by inflammatory chemicals found in swelling.
So sharp knee pain from a neural problem may be caused by:
You can find out lots more about nerve pain on our sister site.
Page Last Updated: 17/11/20
Next Review Due: 17/11/22