When knees are sore, stiff, and swollen from osteoarthritis, several treatment options are available.
Treatment for osteoarthritis (OA) of the knee may start with non-medicinal interventions, such as exercise or weight loss. Another option is over-the-counter (OTC) pain relief medication. Options include acetaminophen (Tylenol), aspirin, or ibuprofen (Motrin, Aleve).
If these treatments do not resolve symptoms, injections are available that can help achieve the desired effects. The United States Food and Drug Administration (FDA) has approved two injections to treat OA of the knee: Hyaluronic acid and corticosteroids.
This article provides an in-depth examination of both types of injection, their uses, and their possible side effects.
Hyaluronic acid injections
Hyaluronic acid injections can help to lubricate the joint and protect the knee against wear and tear.
Hyaluronic acid is a gel-like substance found naturally in the synovial fluid surrounding the joints.
This substance provides lubrication and cushioning. It acts as a shock absorber, helping the bones move smoothly instead of grinding against one another.
People with OA have reduced amounts of hyaluronic acid in their joint fluid. Hyaluronic acid injections can help restore normal levels. These injections not only lubricate the joint, but they may also reduce inflammation and protect the cartilage from further wear and tear.
A doctor or another healthcare provider will give between one and five shots in the knee. The number of shots depends on the brand of hyaluronic acid being used. The injections occur at weekly intervals.
Before giving an injection, the doctor may remove some of the fluid from the knee joint with a needle to reduce swelling. This procedure is called aspiration.
The patient should avoid putting a lot of weight on the affected knee. They should not jog or run, stand for long periods of time, or lift heavy objects.
Typical side effects from hyaluronic acid injections include:
- pain in the knee
- slight swelling
These side effects should resolve after a few days. Applying an ice bag to the knee can help relieve discomfort and prevent swelling after the shots.
In rare cases, people can have more serious side effects, such as bleeding, infection, or an allergic reaction.
Call a doctor right away if any of these symptoms occur:
- severe swelling in the knee
- redness or warmth in the knee
- severe pain
It can take several weeks after the injections before the pain of OA starts to ease up.
The pain relief effects of the injection typically last for about 6 months. Once this wears off, another round of shots or a different treatment is needed. Most insurers will cover a second round of injections 6 months after the first series of injections, so long as the initial treatment was covered and it helped alleviate the pain.
Hyaluronic acid injections do not stop or reverse arthritis. However, they may temporarily ease OA pain in some people who get them. These injections may also improve mobility and movement. People with mild OA are likely to see the greatest benefit from hyaluronic acid injections.
Steroid medicines act in a similar way to the hormone cortisol. Cortisol works on the immune system to reduce inflammation in the body, which also serves to relieve pain. The FDA has approved five different steroid medicines for the treatment of OA. All of them are about equally effective.
Patients will need to visit a doctor for the injection. Doctors sometimes use ultrasound to see where to place the needle. Ultrasound is a type of scan that uses sound waves to create images of the inside of the body. Using ultrasound can help the doctor find the joint space.
The doctor may also give an injection of anesthetic pain relief along with the steroid injection. The anesthetic will provide immediate relief. The steroid should then start working within a few days.
Corticosteroids go to work faster than hyaluronic acid injections, but their effects do not last as long. In some people, corticosteroid injections can help relieve pain and improve movement in the joint. Others do not find any pain relief from these shots.
People with a lot of knee joint damage are less likely to see results. Even if the pain does improve, it may start to come back about several weeks to a few months after the shot.
Although corticosteroid shots are considered safe, it is possible to have side effects such as:
- crystal flares, or irritation in the joint similar to gout
- nerve damage
- in rare cases, infection
- an increase in blood sugar levels, a side effect particularly common in people with diabetes
- thinning of the bones near the knee
If the effects wear off, people receiving the injection may not be able to get another shot right away. Corticosteroid injections are only recommended once every 3 to 4 months. Too many shots can increase the risk of side effects like damage to soft tissues in the knee.
If injections every few months are not frequent enough to relieve the pain, another type of treatment may be needed. If the interval between injections is less than 3 to 4 months, the relief of pain from the injection is not as pronounced and wears off faster.
Talking to a doctor about injections
Speak to a doctor about whether knee injections will help your presentation of OA.
People who think they might have OA of the knee should ask a doctor if knee injections are right for them.
Two other types of injections are available. Although these treatments are still experimental and not yet FDA-approved for arthritis of the knee, some doctors may be able to use them.
Platelet-rich plasma (PRP) injections
These injections use cells called platelets. These help wounds heal and blood clot. The doctor will take the platelets from the patient's own blood. Once inside the knee joint, platelets release substances called growth factors that help fix damaged tissues.
PRP injections may relieve OA pain and improve function, although further evidence is needed before this treatment enters the mainstream.
Stem cell injections
These injections use cells that can develop into any type of tissue in the body to repair damaged cartilage in the knee. Stem cell injection treatment can help reduce swelling and relieve pain.
Before turning to injections, more conservative treatments are available, like physical therapy, heat, ice, and weight loss. Insurers will often not cover injections for osteoarthritis until they receive evidence confirming that conservative treatment has been attempted without success.