Knee Pain When Squatting

A total knee replacement, also known as total knee arthroplasty, is the most common outpatient, elective surgery with over 1 million procedures completed each year. Total knee replacement surgery or partial knee replacement surgery is commonly performed to relieve pain and restore function in individuals with severe knee arthritis or joint degeneration. Partial knee replacement is recommended when the patient has medial or lateral knee arthritis. While many patients experience significant improvement in daily activities after knee replacement surgery, such as improvements with walking, standing, and less pain with general daily activities, some continue to experience pain or difficulty with more demanding movements like squatting. This can be a very frustrating symptom to experience, especially when the surgical knee is otherwise healing well. Most knee replacement patients have a perfect x-ray report from their surgeons, but are still experiencing pain. Squatting is a complex movement that places high loads on the knee joint, particularly at deeper angles of flexion. The lower the squat, the more pain. Squatting and stooping is also a common movement needed to get on and off the floor after surgery. Many knee replacement patients have significant difficulties with this movement. After a knee replacement, several factors can contribute to pain during squats: residual muscle weakness (especially in the quadriceps and glutes), limited joint mobility, soft tissue tightness or laxity, scar tissue, altered movement patterns, and/or lingering inflammation. Additionally, the mechanics of the new knee joint are different from the knee you were born with. A knee replacement may not tolerate deep flexion or rapid, intense loading as well. After a total knee replacement or partial knee replacement, knee pain during squatting becomes a unique issue because the joint mechanics, soft tissue behavior, and neuromuscular control are all altered. While some reasons overlap with those in non-replaced knees, others are specific to the post-surgical state. Understanding these contributing factors is essential for managing expectations, preventing injury, and developing targeted rehabilitation strategies to regain strength and confidence in functional movements like squatting. Here’s a detailed look at why knees might hurt during squatting after knee replacement, related back to the causes we just covered:

Altered Biomechanics Due to the Prosthesis

Any type of prosthesis in the body is not going to feel “right”, especially when it replaces a joint. Not only do they remove key proprioceptive tissues such as the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL), but they also change the shape of the knee. The new knee does not communicate as effectively with the brain right away. The neuromuscular connection takes many months to master as you continue to rehabilitate your knee. Some implants restrict flexion past ~120 degrees, so deep squats may be uncomfortable or mechanically limited. Also, the patella is often resurfaced or realigned during surgery, and may not track naturally under load or force, causing anterior or front of the knee pain when squatting.

Muscle Imbalances & Weakness

Muscle weakness is probably the most common reason for knee pain when squatting, especially if you are in the later phases of recovery around 6+ months post knee replacement surgery. Muscle weakness is especially prominent after surgery due to surgical trauma, pain, knee swelling and pre surgery disuse atrophy. Disuse atrophy means you have been unable to use or strengthen your muscles due to pain and now the muscles have weakened or atrophied. 

The most common muscle to have issues after a total knee replacement or partial knee replacement are the quads. The quads are heavily impacted during surgery and are slow to recover. Weak quads cause difficulty controlling a downward and upward movement during squatting. Many people will feel pain directly in the knee cap, above the knee cap or even below the knee cap. The weakness of the quads can lead to overloading other tissues, such as the patellar tendon and quad tendon. 

Other muscles that are commonly weakened after surgery are the glutes and hamstrings. While these muscles regain strength sooner post surgery than the quads do, they are very commonly weak as we age. Most older adults have weak glute muscles due to hip tightness and lack of exercise. Weak glutes have been directly correlated to knee arthritis since the glutes help control the knee joint. Strengthening your glutes post knee replacement can be very beneficial for squatting, but also for reducing overall knee pain. If you need a safe and effective program to follow, the 4 Week Strength, Balance & Stretching Class is a great online exercise program to take specifically designed for knee replacement patients.

Patients often compensate during squatting due to pain, stiffness, or weakness. It is common to try to avoid pain and use the stronger limb during any movements, but especially squatting since it is a very taxing activity. A common compensation with squatting after a total knee replacement or partial knee replacement is shifting weight to the non-operated leg. This causes continued muscle imbalances due to the asymmetric movement. Other compensations can occur due to more mobility in the surrounding joints. The ankles, hips and low back commonly cause movement errors while squatting. Stretching these areas can help reduce unnecessary stresses to the knee. The knee itself also needs to have adequate flexion (bending) range of motion to properly complete a squat. If you have not reached 120 degrees or more of knee bending, this will cause stiffness and pain when squatting. Most patients need to continue stretching their knee for at least 1 year post surgery. If you are having difficulty with knee bending, please check out the Knee Bending Course, which has proven to help increase knee bending after a knee replacement. 

Scar Tissue and Soft Tissue Restrictions

A less common issue that causes knee pain when squatting is scar tissue. Scar tissue can sometimes adhere around the quadriceps tendon and around the knee cap (patella), limiting movement and causing pain during flexion. Most patients will have a tightness feeling when moving into a deep squat, which can be indicative of scar tissue. The tightness can be felt in the front of the knee near the patella or at the back of the knee joint. Scar tissue is a normal part of the healing process after a knee replacement. Everyone should expect some sort of scar tissue in their knee, but we do not want the scar tissue to cause issues with knee bending range of motion or pain with functional activities such as squatting. 

During a knee replacement surgery, the surgeon has to move things out of the way so he or she can access the knee joint and carefully place the new implant. When the surgeon moves “things” out of the way, this can cause a lot of problems post surgery. The quad muscle and quad tendon become very irritated during surgery. If the tendon was moved or irritated during surgery, pain may persist during loaded flexion.

Overuse or Doing Too Much

Many patients need (and want) to return to normal activities by 4-8 weeks post surgery. This is a common time where pain starts to increase due to the increased activity. The knee joint needs months to remodel and strengthen post knee replacement surgery. Aggressive squatting (too deep, too heavy, too frequent) can overload healing tissues. Also, starting weights or resistance bands too soon post surgery can also lead to pain flare-ups. Strength training should start out slow and steady. You should work through a progressive exercise program for 4-8 weeks to build strength. Starting out with body weight only exercises and building from there is key to ensuring you are not overdoing it. Taking rest days in between is also very important for muscle recovery. If you are experiencing soreness for more than 48-72 hours post exercise, you may be overtraining. If you are experiencing ongoing pain in the knee and you are 3+ months post surgery, you may need to reconsider your exercise routine.

Underlying Conditions or Surgical Complications

Lastly, a less common issue with squatting can be related to the implant itself. If the implant was placed in the knee incorrectly, pain while can continue to persist. If you have sudden increased pain while squatting, sudden clicking in the knee, or a sudden increase in swelling, this indicate an issue with the implant. If these symptoms occur, a call to the surgeon is warranted. Some patients also experience continued low grade inflammation for months and months post knee replacement surgery. This can contribute to pain while squatting and stiffness of the knee joint. Generally, this resolves itself as the knee heals over time. Most people have a reduction in these symptoms by 18-24 months post surgery.