Maybe you can barely raise your arm overhead to blow dry your hair. Maybe if you sit for too long at your desk, your knee will scream with pain. Maybe you are just wondering how you can avoid these common problems. Take a journey into the inner workings of your knees and shoulders. Learn what causes knee pain and shoulder impingement and what you can do to prehabilitate and rehabilitate your body.

Knee Anatomy
The knee joint consists of the femur (thigh bone), the tibia (shin bone), and the patella (kneecap). The patella and the femur form the patellofemoral joint (PF). The patella is located inside the tendon of one of the quadriceps (thigh) muscles. The femur has a concavity or groove that guides the patella up during knee extension (straightening) and down during knee flexion (bending). The underside of the patella has many ridges that are covered with protective cartilage. When the cartilage is healthy and the ridges fit into the femur well, the knee is pain-free. However, if the patella and femur do not mesh well together, the cartilage can wear down and it could predispose a person to PF pain.

Shoulder Anatomy
The bones that form the shoulder are the clavicle (collarbone), scapula (shoulder blade), and humerus (arm). The scapula and the clavicle form the acromioclavicular (AC) joint at the end of your shoulder. You can feel the bony projection of this joint by following your clavicle out to the end of your shoulder. A strong band of tissue called a ligament attaches these two bones. The rotator cuff muscle tendons run under this joint. To protect the tendons from rubbing directly on the bones, fluid-filled sacs called bursae are strategically located around the joint. The entire shoulder joint is surrounded by a fibrous but loose sleeve called the shoulder capsule.

Knee Biomechanics
The patellofemoral joint reaction (PFJR) force is the result of the amount of knee flexion and the force of the quadriceps muscles creating pressure on the patella against the femur [1]. As the knee flexes, the patella is mostly in contact with the femoral groove [2]. This large amount of contact area can help dissipate compressive forces. However, as the knee extends, the patella has minimal contact with the groove. This small contact area cannot disperse compressive forces well. When applying this concept to exercise, large compressive forces can be seen when performing a seated knee extension as the quadriceps have to generate great force to overcome gravity and lift weight. As the knee flexes while squatting, the PFJR force increases, but the load is more evenly distributed across the patella, which is coming into contact with the femur.

Shoulder Biomechanics
The space beneath the AC joint is called the subacromial space. The coracoacromial ligament is the roof of the space and the humerus is the floor. The subacromial space varies with shoulder movement, but one cadaver study showed the mean space to be 11.1 mm without arm movement and decreased to 5.7 mm when the arm is elevated to 90 degrees [3]. Located inside this space are the subacromial bursa, the rotator cuff tendons, and the long head of the biceps tendon. It’s definitely crowded in that small space, and easy to see how an impingement could occur.

The Grind Line
Women and knee pain just seem to go hand in hand. Actually, knee pain, or patellofemoral (PF) pain, is one of the most common disorders that orthopedic and sports medicine physician’s evaluate. The why’s and how’s of PF pain are still a subject of debate. One popular theory blames PF pain on abnormal patellar (kneecap) movement. This faulty movement pattern increases the stress between the patella and the femur (thigh bone) and wears out the cartilage on the underside of the patella [4]. Although the cartilage itself has no pain receptors, the bone underneath does [5]. But the “why” question of PF dysfunction is really an individualized issue and based on a woman to woman case. In some cases, a congenital malalignment of the lower body may be the culprit. Tight and/or weak muscles may be to blame. Overuse of a body part is always going to cause inflammation, pain, and weakness. Knees can also become painful as a result of injuries that stretch ligaments or that bruise the patella. Whatever the “hows” and “whys” may be, the signs and symptoms are generally the same. They run the gamut from swelling, loss of range of motion, a sense of instability where the knee might “give-away,” to pain with prolonged sitting, squatting, and walking up and down stairs.

Treat Your Knees
If your knees are already hurting, your first course of action is to treat the symptoms with rest and ice until the pain lessens or stops. If this has been a chronic, long-standing problem, or if the ice and rest don’t decrease your pain, your next step is to visit an orthopedic surgeon who specializes in sports medicine. Once the painful symptoms are reduced, treating the cause of the problem can be tackled. Strengthening and flexibility of the entire lower extremity from the hip to the foot is important. Strong legs and hips can help decrease stress on the PF joint (see Top Ten Knee and Shoulder Pre- and Rehabilitation Exercises). When the entire quadriceps group is strengthened, it may help change the contact areas between the patella and femur and redistribute the pressures [6]. This, in turn, can relieve painful areas of worn cartilage. Remember, the rule of thumb is that all exercises are performed pain-free.

A Whole Lot of Clicking Going On
That pain or clicking on the top and front of your shoulder during arm movements may be from a shoulder impingement. A shoulder impingement is the trapping of the rotator cuff tendons (primarily the supraspinatus), the subacromial bursa, and/or biceps tendon in the subacromial space [7]. Shoulder impingement is actually a syndrome, where the causes are multifactorial and one problem frequently leads to another. Impingement can be caused by muscular weakness, overuse, and/or degeneration. The shape of the acromioclavicular (AC) joint and shoulder capsule tightness or laxity can also play a role [8].
When the muscles that support the shoulder are weak, the humerus is not stabilized in the joint. The same is true if the shoulder ligaments and capsule are stretched. This instability can cause the top of the humeral head to “bump” into the ligament that creates a roof over the shoulder joint and put pressure on the tendons and bursa that are trapped in between. On the other hand, if the capsule and ligaments are too tight, there won’t be enough space available for all of the structures to move without compression. Poor posture with a forward head and rounded shoulders will close off even more of this small space and cause rubbing of the tendons and bursa. It is even possible that the shape of the AC joint itself may lead to a shoulder impingement syndrome. In addition, excessive overhead use of the shoulder joint without strengthening and stretching can also cause pain.

Treat Your Shoulder
The primary goal of shoulder rehabilitation is to reduce the compression and friction that leads to pain and dysfunction [9]. In acute impingement syndromes, rest, ice, nonsteriodal anti-inflammatory drugs (NSAIDS), and strengthening and flexibility are beneficial and may reverse the syndrome. Again, if these tactics don’t work, consult an orthopedic sports medicine physician. A rehabilitation program should focus on the reason for the impingement. If it is an overuse syndrome, rest and alterations of lifestyle are needed. If muscle weakness or imbalance is the problem, specific exercises should target strengthening the rotator cuff and other stabilizer muscles (see Top Ten Knee and Shoulder Pre- and Rehabilitation Exercises).

What’s A Girl To Do?
So what’s a girl to do if she wants to prevent knee and shoulder injuries or if she’s already got them and needs to rehab them? First, realize that these problems are definitely preventable and easily treated. Second, train smart in the gym and analyze your exercise program to determine if you may be setting yourself up for an injury or if your program contributes to your pain. Keith Meister, MD, orthopedic surgeon, says that women can prevent many injuries by just adding some weight training and stretching into their cardio programs. “I see so many women in my gym spending hours grinding their knees away in spinning classes or raising their arms overhead in aerobics classes and never spending any time with weights. It doesn’t surprise me when they come to my office with knee and shoulder pain. They haven’t prepared their joints with proper strengthening for these stresses,” he says. He recommends acquiring a base of strength and a degree of flexibility to lessen the damage that constant repetitive motions can cause.

Top Ten Knee and Shoulder Pre- and Rehabilitation Exercises
Knee
1. Backward Walking and Stair Climbing
These exercises are best done slowly so that full extension of the knee and the quadricep muscles are emphasized.
2. Straight Leg Raises
Straight leg raises in all directions (to the front, back, outside and inside) strengthen the hip muscles that stabilize the leg during movement. Try these exercises lying down or standing up using ankle cuff weights, in a multi-hip machine, or in the pool.
3. Lateral step ups/downs
Stand with one leg sideways on a step about six inches high. Slowly bend your knee and lower yourself until the heel of your other foot touches the ground. Straighten your knee to return to the beginning position. The key to this exercise is keeping all of your body weight on the leg that’s on the step.
4. Wall sits
Remember this punishment for the bad kids in gym class? With your back against a wall and your legs shoulder-width apart and out from the wall about six inches, bend your knees to squat down to a position not more than 900, or just before any knee pain occurs. Keeping your arms at your sides (and not on your thighs), hold this position for ten seconds. Slide up the wall to return to the starting position. Try ten reps for a great quad burn!
5. Leg Presses and Squats
For rehabilitation, leg presses and squats should be kept in the range of 0o to 30o [10]. If more pain-free range-of-motion can be obtained in the leg press or squat, the best quadriceps strengthening can be found from 88o to 102o [11].

Shoulder
1. Scapular Retraction
Your mother’s advice about standing up straight was right! For scapular retraction exercises, simply stand up tall and squeeze your shoulder blades back. Hold the contraction for five seconds like there is a winning Lotto ticket between your blades that no one can grab. Repeat throughout the day and you’ll get wonderful posture that mother will love!
2. Y,s, T,s, I’s
Lie on your stomach on a flat bench. Lift both arms up toward your head so you make the letter "Y" with your arms; slowly lower and repeat. Bring your arms to your sides to make the letter "T"; lower and repeat. Lift your arms toward your back as close to your body as possible, making the letter "I"; lower and repeat. Try two sets of ten reps in each direction. Progress to weights when you get strong!
3. Straight Arm Lat Pulldown
Use a straight bar on a cable while standing. With straight arms pull the bar down to your thighs. Make sure you’re still holding that Lotto ticket!
4. Empty Can Scaption
Scaption is the plane of motion that the scapula moves in. Perform this exercise standing in front of a mirror. Pronate both hands to a thumbs-down position. Lift your arms up to shoulder height at a 45-degree angle from your trunk, trying not to use your upper traps to lift your arms.
5. Rows
Choose from cable rows, dumbbell rows, T-bar rows or bent-over barbell rows.

References
1. Weber, M.D. and A.N. Ware, Knee rehabilitation, in Physical Rehabilitation of the Injured Athlete, J.R. Andrews, G.L. Harrelson, and K.E. Wilk, Editors. 1998, W.B. Saunders Company: Philadelphia. p. 330-404.
2. Hungerford, D.S. and M. Barry, Biomechanics of the patellofemoral joint. Clin Orthop, 1979(144): p. 9-15.
3. Flatow, E.L., et al., Excursion of the rotator cuff under the acromion. Patterns of subacromial contact. Am J Sports Med, 1994. 22(6): p. 779-88.
4. Grana, W.A. and L.A. Kriegshauser, Scientific basis of extensor mechanism disorders. Clin Sports Med, 1985. 4(2): p. 247-57.
5. Goodfellow, J., D.S. Hungerford, and C. Woods, Patello-femoral joint mechanics and pathology. 2. Chondromalacia patellae. J Bone Joint Surg [Br], 1976. 58(3): p. 291-9.
6. Powers, C.M., Rehabilitation of patellofemoral joint disorders: a critical review. J Orthop Sports Phys Ther, 1998. 28(5): p. 345-54.
7. Neer, C.S.d., Anterior acromioplasty for the chronic impingement syndrome in the shoulder: a preliminary report. J Bone Joint Surg [Am], 1972. 54(1): p. 41-50.
8. Bigliani, L.U. and W.N. Levine, Subacromial impingement syndrome [see comments]. J Bone Joint Surg Am, 1997. 79(12): p. 1854-68.
9. Wilk, K.E., et al., Shoulder rehabilitation, in Physical Rehabilitation of the Injured Athlete, J.R. Andrews, G.L. Harrelson, and K.E. Wilk, Editors. 1998, W.B. Saunders Company: Philadelphia. p. 478-553.
10. Steinkamp, L.A., et al., Biomechanical considerations in patellofemoral joint rehabilitation. Am J Sports Med, 1993. 21(3): p. 438-44.
11. Wilk, K.E., et al., A comparison of tibiofemoral joint forces and electromyographic activity during open and closed kinetic chain exercises. Am J Sports Med, 1996. 24(4): p. 518-27.